Site Visits Related to Combustible Dust

Synthesis Report

	Prepared for:

U.S. Department of Labor

	Occupational Safety and Health 

Administration

	Directorate of Standards and Guidance

	

	Prepared by:

	Eastern Research Group, Inc.

Lexington, MA 02421

January 11, 2010

Table of Contents

  TOC \o "1-5" \h \z \u    HYPERLINK \l "_Toc250920211"  Introduction
and Project Overview	  PAGEREF _Toc250920211 \h  1  

  HYPERLINK \l "_Toc250920212"  1	Industry and Facility Background	 
PAGEREF _Toc250920212 \h  2  

  HYPERLINK \l "_Toc250920213"  2	Combustible Dust Definitions Used	 
PAGEREF _Toc250920213 \h  3  

  HYPERLINK \l "_Toc250920214"  3	Hazard Recognition	  PAGEREF
_Toc250920214 \h  5  

  HYPERLINK \l "_Toc250920215"  4	Hazard Assessment	  PAGEREF
_Toc250920215 \h  6  

  HYPERLINK \l "_Toc250920216"  5	Hazard Communication and Training	 
PAGEREF _Toc250920216 \h  7  

  HYPERLINK \l "_Toc250920217"  5.1.	Content of Material Safety Data
Sheets (MSDSs)	  PAGEREF _Toc250920217 \h  7  

  HYPERLINK \l "_Toc250920218"  5.2.	Training	  PAGEREF _Toc250920218 \h
 10  

  HYPERLINK \l "_Toc250920219"  6	Consensus, Industry, and Insurance
Standards Used	  PAGEREF _Toc250920219 \h  10  

  HYPERLINK \l "_Toc250920220"  7	State and Local Code Enforcement	 
PAGEREF _Toc250920220 \h  11  

  HYPERLINK \l "_Toc250920221"  8	Engineering Controls	  PAGEREF
_Toc250920221 \h  11  

  HYPERLINK \l "_Toc250920222"  8.1.	Primary Engineering Controls	 
PAGEREF _Toc250920222 \h  12  

  HYPERLINK \l "_Toc250920223"  8.2.	Secondary Engineering Controls	 
PAGEREF _Toc250920223 \h  14  

  HYPERLINK \l "_Toc250920224"  9	Administrative Controls	  PAGEREF
_Toc250920224 \h  17  

  HYPERLINK \l "_Toc250920225"  9.1.	Housekeeping Procedures	  PAGEREF
_Toc250920225 \h  17  

  HYPERLINK \l "_Toc250920226"  9.2.	Other Administrative Controls	 
PAGEREF _Toc250920226 \h  19  

  HYPERLINK \l "_Toc250920227"  10	Emergency Response	  PAGEREF
_Toc250920227 \h  20  

  HYPERLINK \l "_Toc250920228"  11	Investigation of Incidents	  PAGEREF
_Toc250920228 \h  20  

  HYPERLINK \l "_Toc250920229"  12	Regulatory Approaches	  PAGEREF
_Toc250920229 \h  21  

  HYPERLINK \l "_Toc250920230"  13	Economic Impacts and Benefits	 
PAGEREF _Toc250920230 \h  25  

  HYPERLINK \l "_Toc250920231"  14	Impacts on Small Entities	  PAGEREF
_Toc250920231 \h  27  

  HYPERLINK \l "_Toc250920232"  15	Compliance Assistance	  PAGEREF
_Toc250920232 \h  27  

  HYPERLINK \l "_Toc250920233"  16	References	  PAGEREF _Toc250920233 \h
 29  

 

Abbreviations

ERG		Eastern Research Group, Inc.

Kst			deflagration index

LOC		limiting oxygen concentration

MEC	 	minimum explosible concentration

MIE		minimum ignition energy

MSDS		Material Safety Data Sheet

NFPA		National Fire Protection
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浤湩獩牴瑡潩൮浰硡उ洉硡浩浵攠灸潬楳湯漠敶灲敲獳
牵⁥倍䕐उ数獲湯污瀠潲整瑣癩⁥煥極浰湥൴卐्瀉潲
散獳猠晡瑥⁹慭慮敧敭瑮

μm			micron (or micrometer) 

Introduction and Project Overview 

Under contract to the Occupational Safety and Health Administration
(OSHA), Eastern Research Group, Inc. (ERG) conducted site visits to six
industrial facilities to gather information on the development and
implementation of combustible dust recognition, prevention, and
protection programs. This report documents common themes and important
observations from the six site visits. More detailed insights on the
individual visits can be found in the facility-specific site visit
reports.

ERG implemented this project according to specifications in a Project
Protocol (ERG, 2008), which OSHA reviewed and approved in December,
2008. As the protocol describes, ERG recruited facilities to host site
visits through telephone calls, focusing on industrial sectors
identified by OSHA. The six site visits were conducted between April and
November, 2009. During that time, ERG visited two food manufacturing
facilities, two metals processing facilities, a paper mill, and a
pharmaceutical manufacturing facility. Each visit lasted 2 or 3 days and
was conducted by chemical engineers from ERG and a fire protection
engineer, a consultant to ERG. Information on the facilities’
combustible dust safety programs was obtained during guided facility
tours; interviews with operators, process engineers, safety personnel,
and facility managers; and document reviews. Although the site visits
were not designed to assess facility adherence to National Fire
Protection Association (NFPA) consensus standards or compliance with
OSHA regulations, this report identifies certain instances where
facilities did not comply with these guidelines and regulations. During
some visits, samples of selected materials were collected and sent to
OSHA’s laboratory in Salt Lake City and analyzed for explosibility and
combustibility parameters. 

The remainder of this report documents common themes and salient
findings from the six site visits, based on the judgment of the site
visitors. While this report presents summary information on selected
facilities’ perspectives and experiences with combustible dust, the
report does not document every observation made during the site visits.
Readers should refer to the individual site visit reports for a more
complete account of observations made throughout this project. Moreover,
because the project is based on visits to only six industrial
facilities, the report should not be viewed as a comprehensive
nationwide survey of current combustible dust safety programs. 

The remainder of this report organizes the site visitors’ observations
into 15 different topics. These topics were selected because they
parallel the organization of information in OSHA’s Advanced Notice of
Proposed Rulemaking (ANPR) for combustible dusts (OSHA, 2009b). Some
observations are relevant to multiple topics. Rather than repeating
these observations throughout the report, such observations are
described in detail once, and then referenced in other sections as
appropriate. 

Industry and Facility Background

Site visits were conducted at two facilities in the food manufacturing
industry, two facilities in the metals processing industry, one paper
mill, and one pharmaceutical manufacturer. Facilities were visited at
locations throughout the United States. The facilities varied greatly in
terms of many factors: the number of employees at each facility ranged
from 80 to more than 2,000; some facilities had only a few production
lines while others had more than 10; and some production processes were
more than 30 years old while others were constructed within the last 5
years. The site visit reports include more detailed information on each
facility visited, and this section describes the facilities’ in-house
and corporate resources for addressing combustible dust safety issues: 

The facilities had varying in-house capacity for conducting technical
analyses and evaluations of combustible dust safety issues.
Specifically, the facilities had between one and five employees who
worked nearly full-time on occupational safety issues, and these
individuals were responsible for implementing and overseeing a broad
range of safety (and environmental) programs. At the smallest facility
visited, only one person worked exclusively on health and safety issues,
and she reportedly spent approximately 1% of her time on combustible
dust safety issues (largely because most of her time was spent ensuring
compliance with other OSHA standards, particularly process safety
management). The individuals who worked on combustible dust issues had
varying academic backgrounds and professional experience. 

Every facility visited was part of larger corporations, and the
corporations had varying levels of influence on the individual
facilities’ combustible dust safety programs. At one extreme, a
corporation had its own “process safety” staff that was dedicated to
providing technical support on combustible dust (and many other safety
issues) to the company’s individual facilities. This corporation was
actively engaged with facility-specific safety issues and issued
corporate-wide policies on many topics related to combustible dust (see
Section 6 for further information). At the other extreme, two of the
facilities visited received minimal support from corporate officials on
combustible dust safety issues. 

When characterizing combustible dusts or constructing or implementing
major modifications to processes involving combustible dust, the
facilities relied to varying degrees on external engineering and design
firms and consulting companies. Some facilities relied entirely on these
external resources, while others sought external engineering and design
support only for specialized tasks not adequately covered by in-house
expertise. 

The facilities’ experiences with insurance underwriters varied. Each
facility’s insurance underwriter reportedly conducted annual visits to
evaluate fire protection measures and other safety issues. Some
insurance underwriters played a very active role in informing and
educating facilities about combustible dust safety issues, while other
insurance writers offered limited to no insight on the matter. One
insurance underwriter was noted as being particularly engaged in
facilities’ combustible dust safety programs (see Section 6 for more
information). 

Combustible Dust Definitions Used

The facilities visited for this project typically deferred to NFPA
definitions for identifying combustible dusts. However, the various
definitions published in current and former NFPA standards are not
consistent and may change in future editions of these standards.
Specific definitions cited during the site visits included
“combustible metal dust” as defined in NFPA 484; “combustible
dust” as defined in NFPA 499 and NFPA 654; and “agricultural dust”
as defined in NFPA 61. These definitions differ primarily in terms of
whether they specify particle size cut-offs. 

Given the lack of a universally accepted definition of combustible dust,
nearly every facility representative expressed interest in precisely how
OSHA’s standard will define the term. Some facility representatives
preferred a definition based on objective criteria (e.g., specified
ranges of particle sizes, deflagration indices, and so on) while others
facility representatives advocated for more open-ended definitions
(e.g., “combustible dust” as currently defined in NFPA 654). See
Section 12 for additional discussion of this issue.

Every facility visited in this project had some laboratory analytical
data that characterized materials that could be classified as
combustible dusts. Detailed information on these testing data can be
found in the facility-specific site visit reports. The testing data that
ERG reviewed quantified various parameters, including particle size
distribution, deflagration index (Kst), moisture content, maximum
explosion overpressure (pmax), minimum explosive concentration (MEC),
and minimum ignition energy (MIE). Facility representatives raised the
following issues when discussing how laboratory analytical data might be
used to help define which materials are combustible dusts:

While facilities recognized the need to characterize their materials,
facility representatives also noted the need for direction and guidance
from OSHA on many aspects of testing combustible dusts: What materials
must be tested (e.g., raw materials, intermediates, products, settled
dusts, material from dust collectors)? How often must this testing
occur? What parameters must be measured? Will facilities or their
suppliers be expected to provide testing data? Will OSHA publish
cut-offs for particle size, moisture content, and other properties when
defining combustible dusts? What laboratory analytical methods must be
used? Under what circumstances is it acceptable for facilities to refer
to published data for comparable materials? 

Facility representatives generally acknowledged the importance of having
extensive testing data for their materials. However, some
facilities—particularly the larger facilities that used many different
combustible materials in their processes—expressed concern about the
costs associated with running a full battery of laboratory tests on all
materials that are, or may generate, combustible dusts. (Refer to
Attachment 1 of this report for laboratory testing costs that commercial
laboratories quoted for two facilities.) To illustrate this concern, one
of the food manufacturers processed dozens of different dry ingredients,
which were subsequently milled, mixed, and blended into many mixtures;
and these various materials were found throughout the facility in
different particle size fractions (e.g., finer dusts settled on
surfaces, coarser material captured in dust collectors). According to
representatives at this facility, hundreds of laboratory tests would be
required to fully characterize these materials.  

Most facilities shared testing data with the site visitors. The
facilities generally tested bulk raw materials and products believed to
pose the greatest explosion hazards, but these materials may not have
reflected hazards associated with settled dusts in the workplace or
material from dust collectors. Even though the settled dusts and
collected dusts are chemically similar to their respective raw materials
and products, these dusts can have considerably varied particle size
distributions and therefore would be expected to exhibit different
explosion hazards. Facilities would likely benefit from guidance on how
to select materials for testing, especially when limited numbers of
samples will be collected (e.g., testing for milled products instead of
un-milled products, consideration for testing of settled dusts or
material collected in dust collectors). Some facility contacts stated
that they were not sure what parameters should be measured by
laboratories. 

One facility representative said suppliers, under OSHA’s Hazard
Communication standard, should be obligated to provide facilities a
broad range of testing data for combustible dusts and materials that can
generate combustible dusts under normal processing and use. Section 5 of
this report expands on this concern. 

Hazard Recognition

Employees at every facility visited exhibited strong awareness of which
materials are combustible dusts. Facilities generally did not assign
specific employees responsibility for making this determination. Rather,
identification of combustible dusts occurred through various means:
experience from process operators, engineers, and safety staff; input
from corporate officials and insurance underwriters; “common
knowledge” (e.g., facilities that handled certain pyrophoric metallic
dusts did not need to conduct research to determine that these materials
were combustible); and rules of thumb (e.g., finely milled grain
products and starches are likely combustible dusts). While facilities
were generally aware that Material Safety Data Sheets (MSDSs) contain
information about potential combustible dust hazards, MSDSs did not seem
to be a primary source of information for identifying combustible dusts.
Refer to Section 5.1 for facility feedback on MSDSs and the role that
suppliers play in providing quantitative information on potential
combustible dust hazards. Representatives from all six facilities said
that local fire authorities offered no useful insights on determining
which materials are combustible dusts. 

When seeking quantitative information on combustibility and
explosibility, facilities tended to have samples analyzed by
laboratories for various parameters or seek reported values from the
literature. In general, most facilities had materials tested only once
for explosibility parameters and did not re-test these materials,
presumably because the material composition did not change considerably
with time. 

Some facilities apparently assumed that testing data for a given
material, whether reported by a laboratory or taken from a publication,
apply wherever that material is found in the same chemical form, without
regard for changes in physical properties (e.g., particle size
distribution, moisture content). This assumption may have led to
facilities incorrectly concluding that certain materials were not
combustible dusts. For example, one facility used testing data for its
bulk product to conclude that a sugar compound was not a combustible
dust. However, the mean particle size for the bulk product was likely
considerably greater than that of settled dusts and one of the
facility’s milled products; and these finer materials—though
chemically identical to the bulk product—would be expected to exhibit
different explosibility properties. As another example, multiple
facilities referred to published parameters (e.g., deflagration indexes,
minimum ignition energies) for certain materials when evaluating
potential combustible dust hazards, even though those published accounts
did not document the particle size of the tested material. 

Note: 	ERG contacted dozens of facilities before identifying the six
facilities that agreed to host site visits. When other facilities were
asked why they chose not to participate, the facility representatives
often asserted that their operations did not generate combustible dusts,
even though some worked in industries known to have more frequent
combustible dust fires or explosions (e.g., aluminum foundries). Thus,
it is possible, if not likely, that facility recognition of combustible
dust hazards is much poorer than implied by the six facilities that were
visited in this project. 

Hazard Assessment

ERG asked representatives from all six facilities if they have conducted
hazard analyses on processes involving combustible dusts. Examples of
some facility practices follow:

One facility followed its corporate policy of applying process safety
management (PSM) requirements to every chemical production operation,
regardless of whether the process included chemical usage that would
actually trigger PSM applicability. Due in part to this policy, this
facility conducted detailed hazard analyses on every process involving
combustible dusts. Groups of up to 12 employees—typically safety
professionals, engineers, operators, and maintenance
personnel—conducted the hazard analyses and addressed many topics
included in PSM hazard analyses: human factors, siting, operating
procedures, process safety information, mechanical integrity, and
incident investigations. 

One facility developed a spreadsheet-based approach to prioritize its
resources for retrofitting existing processes with controls to minimize
combustible dust hazards. This facility had hundreds of unit operations
that processed materials containing combustible dust and developed a
scoring scheme to determine which unit operations should receive
immediate attention. In this scheme, each unit operation was ranked
according to several factors: fuel properties (e.g., type, quantity,
particle size, potential for suspension); operating temperatures;
potential ignition sources (e.g., static, friction, hot work); proximity
to employees; and history of past fires and explosions. The outcome of
this scoring scheme was a composite rank that was qualitatively
indicative of each unit operation’s combustible dust hazard. ERG site
visitors found this “risk assessment” approach to be a useful tool
in ranking hazards and prioritizing control upgrades for individual
process.   

Another facility established “Dust Explosion Protection Hazard
Analysis Criteria” to determine what specific controls may be
warranted on all newly installed equipment. The criteria were organized
into a decision tree that asked a series of questions (e.g., Is dust
combustible? Is equipment confined? Is the particle size less than 420
microns? Are ignition sources present? Has explosibility testing been
conducted?). Based on answers to these and other questions, the decision
tree would indicate whether equipment explosion protection is required,
whether fire protection options are necessary, and other design
considerations. A second tier of questions then provided additional
specificity on the required controls. For instance, if the first tier of
questions indicates that equipment explosion protection is needed, the
second tier of questions would help determine what type of protection
(e.g., venting, flame quench, suppression) is most appropriate. In
short, this facility’s hazard analysis criteria walked process safety
engineers through the process of determining whether protection is
required and, if so, what type of protection is preferred. 

Hazard Communication and Training

Though the site visits were not designed to assess the overall
effectiveness of facilities’ hazard communication programs, this
section documents several observations pertaining to hazard
communication in the context of combustible dusts. Observations are
organized into two topics: information documented on Material Safety
Data Sheets (Section 5.1) and information conveyed during employee
training programs (Section 5.2). 

Content of Material Safety Data Sheets (MSDSs)

During site visits, ERG reviewed approximately 100 Material Safety Data
Sheets (MSDSs) for both (a) materials suspected to be combustible dusts
and (b) materials that could generate combustible dusts under normal
conditions of use. The extent of documentation of potential combustible
dust safety hazards varied greatly across these MSDSs. In cases where
MSDSs acknowledged and characterized combustible dust safety hazards,
relevant information was typically found in sections on firefighting
measures, accidental release measures, handling and storage, and
stability and reactivity. Following are several general observations
about the MSDSs that the site visitors reviewed:

Quantitative information. MSDSs exhibit great variability in terms of
quantifying flammability and explosibility: some MSDSs presented only
qualitative descriptors of hazards, while others included quantitative
data on various parameters. Of the MSDSs reviewed, the parameters that
were most frequently quantified were minimum explosible concentration
(MEC), lower explosive limit, and cloud ignition temperature. Following
is an excerpt from the MSDS that included the most detailed quantitative
information (in this case, for a modified food starch):

Lower explosive limit: 	60 g/m3.

Starch is a class St1 dust at normal moisture level.

Minimum ignition energy (MIE): > 30 mJ at normal moisture level.

Pmax: 9.5 bar

Kst: 170 bar-m/s

Layer ignition temperature: > 450 oC.

Auto ignition temperature: 170 oC. (Above this temperature starch will
self-heat.)

Facility representatives also exhibited different expectations regarding
the anticipated level of quantitative information in MSDSs. One facility
contact noted that his company processes more than 150 raw materials
that are likely considered to be combustible dusts; however, the
facility received complete testing data for only 35% of these materials.
The specific testing data requested from suppliers and manufacturers, in
this case, were MEC, Kst, MIE, and pmax. This facility recommended that
OSHA clarify whether the supplier or facility is obligated to test for
these parameters.

Qualitative information. Most of the MSDSs that ERG reviewed had some
qualitative characterization of potential fire and explosion hazards;
however, the level of detail widely varied. At one extreme, certain
MSDSs included very generic information (e.g., “avoid dusty
conditions”) without acknowledging the full range of hazards and how
they can be minimized or controlled. At the other extreme, some MSDSs
offered much more detailed and thorough characterization of the
potential hazards and means for controlling them.  For example, one MSDS
included the following:

Sources of ignition can start a fire on fine particle sizes… Layers of
3-micron diameter dust are susceptible to spontaneous ignition.
[Material] burns with very little flame but with large quantity of
heat... Do not spray water on burning powder, fines, chips, or dust as
violent explosion may occur. This hazard increases with finer particles.
If a fire starts in a mass of wet metal fines, such as a drum of damp
machining chips, an explosion and a very high temperature flash
radiation may follow the initial fire. Therefore, when in doubt,
individuals should leave and not attempt to extinguish the fire but let
it burn out. The explosion characteristics of such material are caused
by the hydrogen and steam generated by the burning mass... Carbon
dioxide is not effective in extinguishing burning [material] and will
accelerate combustion. Fire extinguishers should not be pointed directly
at the burning material, so as not to stir up and aggravate the fire. 

Inclusion of hazards for “normal conditions of use.” According to
OSHA’s recent guidance on hazard communication for combustible dusts
(OSHA, 2009c), suppliers and importers must consider the potential
hazards of materials “that may occur under normal conditions of use”
and address known hazards on MSDSs. The MSDSs that ERG reviewed
exhibited considerable variability in meeting this requirement,
particularly in terms of various food items sold in bulk but
subsequently milled at other facilities and metal products sold as
“articles” (e.g., billets, ingots, rods, plates) but subsequently
machined at other facilities. 

To illustrate this point, ERG reviewed MSDSs for two bulk metal
“articles” that facilities sold to their customers, who then
machined the products. Both of these articles were pure forms of
combustible metals listed in NFPA 484. One MSDS provided no information
on potential hazards associated with machining the object, but the other
MSDS included the following disclaimer: 

This metal in its present state is an “article” as defined in 29 CFR
1910.1200. However, changing its shape or form may promote a chemical or
fire hazard… Shiny, odorless, metal that presents little or no unusual
hazard if involved in a fire in its solid mass state. When in a particle
state, it can be flammable to pyrophoric depending on its size, surface
area, and if wet or damp.

ERG also notes that one supplier completely avoided the issue of hazards
associated with normal conditions of use by claiming on an MSDS:
“…we cannot predict the uses of [wheat flour] and deny any liability
for injuries or illnesses that might be occasioned by unanticipated or
non-normal uses.” As a result, the supplier provided limited
information on this material’s MSDS, and the facility that purchased
and subsequently processed the wheat flour may not have been fully
informed of potential hazards.

Regulatory interpretations. In some cases, suppliers of specific food
items provided facilities letters or other communications claiming that
certain materials were exempted from OSHA’s Hazard Communication
standard. The rationale provided by these suppliers follows:

(1) Food grade products intended for edible uses do not require Material
Safety Data Sheets (MSDS) to comply with OSHA regulation 29 CFR
1910.1200 (The Hazard Communication standard). Under the standard, MSDSs
are only required for hazardous chemicals. Hazardous chemicals are
defined as any chemical which is a physical or health hazard. Physical
or health hazards are further defined and Appendix B of the standard
describes criteria used to determine whether or not a chemical is to be
considered hazardous. Foods regulated under The Food, Drug, and Cosmetic
Act (which all of our foods and food ingredients are) do not meet any of
the criteria which require them to be listed as hazardous. Therefore,
our rices and rice by-products do not require MSDSs.

(2) [Company] believes its wheat flour and other milled wheat products,
for human consumption, are not hazardous materials according to the OSHA
Hazard Communication standard (29 CFR 1910.1200). These products are
labeled according to the Federal Food, Drug, and Cosmetic Act and are
exempt from further OSHA or EPA labeling requirements.

These interpretations are included in this report to inform OSHA of
circumstances by which facilities may not be fully informed of potential
combustible dust hazards. It is outside the scope of this project to
comment on whether these suppliers’ regulatory interpretations are
correct. 

Training

Every facility visited offered numerous different initial and refresher
training programs to employees, contractors, and visitors. Training
topics varied across the facilities, but typically addressed plant
security, personal protective equipment, emergency response, standard
operating procedures, lockout/tagout, confined space entry, hot work
permits, smoking, and chemical safety. Most facilities had at least one
training course that addressed combustible dust safety issues at some
point, but only one facility developed and offered a training course
devoted entirely to this topic. Multiple different delivery methods were
used for the training, including classroom settings, videos, interactive
courses on CD-ROM, and on-the-job training. As time permitted, site
visitors viewed the various training materials, some of which did not
mention unique hazards of combustible dusts, while others offered
detailed information on this topic. 

Consensus, Industry, and Insurance Standards Used

The facilities listed various standards used for identifying combustible
dusts and controlling and mitigating their hazards. Specific examples
follow:

NFPA. Every facility that ERG visited was aware of NFPA standards on
combustible dusts (e.g., NFPA 61, 484, 654), though the awareness of
specific requirements varied greatly across these facilities. Some
facilities had employees who are actively engaged in the development of
NFPA standards, either by serving as Technical Committee members or by
commenting on proposed revisions to the standards. 

Industry. The six facilities that ERG visited were not aware of any
industry standards specific to combustible dusts. Some of these
facilities are members of industry-specific trade associations, though
none of these associations has published combustible dust safety
standards. One facility noted that the International Titanium
Association may soon be developing a manual to describe safe practices
for using and handling titanium (including titanium dusts). Further,
facility representatives noted that other industry trade associations
were actively tracking OSHA’s rulemaking process, though the
associations were not necessarily developing their own standards. 

Insurance. The six facilities that ERG visited were insured by different
underwriters. Of these, only one (Factory Mutual) was identified as
having developed extensive property loss prevention guidelines specific
to combustible dust (FM, 2009) and requiring its policyholders to adhere
to these guidelines, though exceptions can be negotiated. All six
facilities noted that their insurance underwriters conducted inspections
at least annually, but the extent to which those inspections addressed
combustible dust varied. Further, some facilities identified their
insurance underwriter as a trusted resource for current, technical
information on combustible dust safety issues, while others noted that
they tended to rely on other resources because their insurance
underwriter did not seem to offer strong expertise on combustible dusts.


Other. One of the six facilities was part of a corporation that had
recently prepared a process safety technical guideline on combustible
dusts that applied to all of the corporation’s research and
manufacturing facilities. These written guidelines were prepared by
corporate process safety officials, with input and comment received from
individual facilities. Many references were considered when developing
these guidelines (e.g., NFPA standards; Eckhoff, 2003; Bartnecht, 1981;
Barbauskas, 2003). The guidelines are not publicly available
information. 

State and Local Code Enforcement

For all six facilities visited, the local fire marshals and fire
departments conducted periodic inspections of the facilities, but these
inspections focused primarily on general fire detection and suppression
principles. The local fire authorities provided virtually no specialized
expertise in combustible dust safety issues, particularly for the
facilities that were located in sparsely populated areas and served by
volunteer fire departments. In most cases, the industrial facilities
actually educated the fire marshals (rather than fire marshals educating
the facilities) about the unique and specific combustible dust safety
issues found at their sites.

Representatives from all six facilities noted that their local fire
marshals did not suggest adherence to NFPA standards specific to
combustible dust. Therefore, at all six facilities visited, either (1)
compliance with various NFPA standards was not required in their
jurisdictions or (2) compliance was required but the local fire marshals
exhibited limited to no awareness of the potentially applicable NFPA
standards and how to evaluate facility compliance. 

Engineering Controls

ERG site visitors observed a broad array of industrial processes, which
included many unit operations that potentially posed combustible dust
hazards (e.g., dryers, ovens, dust collectors). This section reviews
ERG’s observations regarding the various engineering controls
facilities employed to prevent an incident from occurring (Section 8.1)
or to minimize the effects of an incident after it had been initiated
(Section 8.2). The need for engineering controls ultimately depends on
the potential hazards associated with the materials being processed. In
many cases, lack of extensive testing data complicated efforts to assess
the effectiveness of facilities’ engineering controls. For instance,
because some facilities lacked MIE data for their main products, site
visitors could not assess whether sufficient electrostatic prevention
measures were in place. Many of the engineering controls that site
visitors observed were installed more than 10 years ago, and original
design specifications, hazard analyses, and other documentation were no
longer available for review. 

Primary Engineering Controls

This section summarizes site visitors’ observations regarding primary
controls designed to prevent hazards from occurring. Observations are
organized according to specific types of engineering controls listed in
the combustible dust ANPR. This section covers only those controls that
were observed at the six facilities that participated in this program:

Features to prevent accumulation of dust on surfaces. Nearly every
facility faced challenges of preventing dust accumulations on surfaces,
particularly overhead horizontal surfaces. One facility addressed this
by installing overhead oscillating fans that continuously blew air over
and near surfaces where dusts previously accumulated. The fans proved
highly effective at reducing accumulations within a 35-foot radius and
minimized the need to periodically clean these overhead structures,
which was previously conducted manually with explosion-proof vacuum
cleaners. Further, emergency stop switches were installed in the working
area, which employees were instructed to activate in the event of a
fire; this measure was implemented to ensure that fans do not suspend
smoldering or burning material and possibly exacerbate a dangerous
condition. Industrial hygiene evaluations verified that operation of the
fans did not lead to excess noise exposure, and the fans did not
adversely affect employee comfort. 

Oxygen concentration reduction. Three facilities operated certain
production processes under inert atmospheres: two facilities used argon,
and the other used nitrogen. These processes were all equipped with
oxygen monitoring devices to ensure that oxidant concentrations remained
at safe levels. Original design specifications were not available at
these facilities, so site reviewers commented primarily on their
potential compliance with specifications in NFPA 69. While process
engineers generally knew the oxygen concentration that would trigger
process shutdown and other measures, they had less awareness for how
that oxygen concentration was derived. Additionally, site visitors had
some concerns about the reliability of sampling and monitoring
instrumentation used to measure oxygen concentrations—a critical
component of this engineering control. One facility commented on
technical difficulties associated with installing continuous oxygen
monitors in unit operations that were not stationary, such as rotating
blenders. 

Foreign material separation devices. Only two of the facilities used
equipment (e.g., scalping screens, magnetic separators) to remove
metallic scrap in process locations where tramp metal can introduce
serious spark-producing hazards, such as upstream of milling operations.
Use of these devices was observed only in food manufacturing facilities
and was motivated largely by product safety concerns, rather than out of
concern regarding combustible dust hazards. 

Monitoring and alarms for abnormal conditions. Facilities employed
various monitoring systems to detect abnormal operating conditions. Some
of these systems monitored parameters for production quality control
purposes, while others were implemented specifically to detect
potentially hazardous situations associated with combustible dusts.
Examples of monitoring systems observed included temperature sensors in
dryers and dust collectors, oxygen analyzers in processes required to
operate under inert atmospheres, and low-level water sensors in wet dust
collectors. Very few instances were observed where facilities operated
monitoring devices (e.g., flame sensors, spark/ember detection systems)
that might detect the presence of a fire that outlet temperature
monitoring equipment might otherwise fail to detect. 

Automatic interlocks, shutoffs, or overflow systems. Many examples of
automatic interlocks and shutoffs were observed at the six facilities.
At one facility, for instance, metal cutting operations could not be
operated unless the water reservoir in the wet dust collectors was at a
certain level. Processes operating under inert atmospheres could not be
started until measured oxygen concentrations were safely below the
limiting oxygen concentration (LOC) for a specified time frame. In
addition, site visitors also noted several instances where the absence
of interlocks was problematic. At one facility, for example, multiple
dust-generating operations vented to a single wet dust collector.
Operators had to visually verify that the proper ductwork connections
were in place and then confirm that the wet dust collector was ready for
operation (e.g., sufficient water reservoir). In cases like these,
engineering controls (interlocks) would help guarantee that dust
collectors were functioning properly before dust-generating operations
could be initiated. 

Manual emergency controls. Several facilities had manual emergency
controls that, when activated by employees, would trigger various
instantaneous actions. Examples included employee-activated steam
suppression in dryers, argon quenches in metal milling and grinding
operations, and fuel cut-offs for gas-fired dryers and roasters.

Class II electrical equipment and wiring. The facilities exhibited
widely varying appreciation for designating hazardous locations and
ensuring use of equipment rated for those designations. Some facilities
conducted very thorough process evaluations to identify and delineate
hazardous locations, and they also ensured that all equipment operating
in Class II locations was approved for the hazard classification.
However, other facilities were not as thorough in this regard, whether
completely failing to designate Class II locations in the first place
(as suggested by sample results collected by site visitors) or using
equipment (e.g., propane-powered forklifts, vacuum cleaners) not rated
for combustible dust atmospheres in their designated Class II locations.
Further, at one facility, site visitors noted visible dust accumulations
inside reportedly “dust-tight” electrical equipment enclosures.  

Grounding, bonding, and other electrostatic controls. Facilities adopted
different strategies for controlling electrostatic discharge. In some
cases, the adequacy of these controls could not be assessed due to the
lack of sufficiently informative testing data (e.g., MIE) for certain
materials. In other cases, extensive electrostatic controls were applied
in some parts of facilities, but not in others. For instance, one
facility grounded and bonded its pneumatic conveying lines in some but
not all of the production areas involving the same combustible dust
materials; further, one facility that processed a highly sensitive
material (MIE < 4 mJ) had extensive grounding and bonding of facility
equipment, but did not have comparable controls (e.g., use of grounding
straps, conductive shoes, static-dissipative clothing) to ensure that
employees themselves did not contribute to electrostatic hazards. 

Secondary Engineering Controls

This section summarizes site visitors’ observations regarding
secondary controls designed to minimize the effects of an incident after
it has been initiated. The observations are organized according to
specific secondary engineering controls listed in the combustible dust
ANPR. This section covers only those controls that were observed at the
six facilities that participated in this program:

Dust collectors. Every facility that ERG visited had dust collectors,
and these varied tremendously in terms of placement, design, operation,
and controls. Some facilities had “dry” dust collectors (e.g.,
baghouses) in which collected material was separated from an air stream
and later removed from the device, and others had “wet” dust
collectors in which collected material was collected in a water
reservoir and eventually removed as sludge. Given the commonplace use of
this technology to collect combustible dusts and the frequency with
which fires and explosions originate in these devices, the following
paragraphs present detailed observations about the facilities’ dust
collectors. However, most facilities no longer had extensive
documentation of the original engineering evaluations and design
specifications for their dust collectors.

The overwhelming majority of dust collectors that ERG observed were
located inside production buildings. Although most dust collectors
inside buildings were placed alongside or in close proximity to external
walls, many exceptions were observed, primarily for the older facilities
and processes. Later sections of this report comment on the potential
regulatory implications of the placement of these devices. 

Many dust collectors observed during the site visits vented exhaust air
to the outdoor, ambient environment. However, numerous exceptions were
observed where dust collector exhaust air was returned into the
workplace, sometimes after passing through one or multiple particulate
filters. Two reasons were cited for preferring to return dust
collectors’ exhaust air to workplaces: (1) environmental permitting
regulations in some jurisdictions require facilities to obtain air
permits before constructing any new vent from a production area to
outdoor air—a situation that presented a disincentive for venting dust
collector exhaust to the ambient environment; and (2) venting exhaust
air to the ambient environment increases demand for air conditioning in
the summer and heating in the winter. In almost every instance where
facilities returned exhaust air from dust collectors to the workplace,
no explosion isolation devices were installed at the dust collectors or
the ductwork, which raised concern about deflagrations or explosions
starting in a dust collector and propagating throughout a facility. 

The most commonly used explosion protection technology in dust
collectors was explosion panels designed to vent material during an
explosion through ductwork to the outdoors; however, a large number of
dust collectors were operating without any such controls. The design of
the explosion venting varied greatly. In most cases, explosion vents
were relatively short (10 feet or less) and directed outdoors, but some
exceptions were observed. For example, duct work for one explosion vent
was approximately 50 feet long, including a 90-degree bend, and site
visitors questioned the effectiveness of this design. In this particular
case, construction of a shorter explosion vent was not feasible without
completely redesigning an entire process; however, other forms of
controls could have been employed to prevent or suppress explosions in
the dust collector. In another case, an explosion vent from a dust
collector inside a production building was not connected to any
ductwork: thus, an explosion in this dust collector would vent directly
into the workplace. Finally, one dust collector that was placed outdoors
alongside a building was equipped with explosion panels, but these were
placed on the side of the dust collector that faced the building, rather
than the side that faced away from the building. 

Most dust collectors that ERG observed were not equipped with measures
(e.g., metal detection systems at inlets, spark and ember detection
systems) that would help detect ignition sources or fires inside
equipment, and few were equipped with measures that would extinguish
fires before they could propagate into larger events. As an exception,
one facility had linear heat detectors installed on some of its dust
collectors, and these detectors activated an argon quench when
measurements exceeded a trigger level. Further, as noted above, dust
collectors (and interconnecting ductwork) were generally not equipped
with explosion isolation devices, raising concern about explosions
propagating from the collector back to the process equipment. 

Individual site visit reports document other observations in which dust
collector design and operation were apparently not compliant with NFPA
standards. For instance, some facilities vented exhaust from multiple
processes through manifolded ductwork into a single dust collector,
without having conducted a hazard evaluation or installing appropriate
explosion isolation devices. 

Deflagration suppression systems. Three facilities employed deflagration
suppression technology to control potential explosion hazards. At one
facility, this technology was installed at raw material storage silos.
These systems were designed to inject large volumes of sodium
bicarbonate into the silos upon detection of elevated pressures. Though
facility representatives had confidence in the systems’ effectiveness,
they also had reservations about using this technology. For example, the
facility currently pays approximately $8,000 a year to train employees
to inspect and maintain these explosion suppression systems. While these
costs are substantially lower than the initial purchase and installation
costs of the deflagration suppression systems, the facility noted that
the cumulative long-term maintenance costs can be significant. Further,
the facility was concerned about the possibility of “false trips”
that can contaminate storage vessels and large quantities of raw
materials. (Note: The particular suppression agent used in this case was
compatible with U.S. Food and Drug Administration requirements for food
additives, which helped address concerns for food manufacturing
facilities.) 

Manual fire suppression equipment. Facilities had varying types of
manual fire suppression systems, but specific challenges associated with
manual fire suppression equipment were observed primarily at the metals
processing facilities, where Class D extinguishing agents were required.
One facility researched numerous candidate Class D agents and found
sodium chloride (“table salt”) to be most effective. At this
facility, employees extinguished smoldering metal fires by scooping or
shoveling salt from barrels and pouring the salt directly on and around
fires. This approach raised concern to site visitors because employees
had to come in very close proximity to fires in order to suppress them.
The facility had considered other means for delivering the table salt to
the fires, but most extinguishing systems result in a high pressure
stream of the suppression agent, which has the potential for spreading a
combustible metal fire instead of extinguishing it. The facility was
actively researching various combinations of Class D extinguishing
agents and delivery systems that would allow employees to effectively
suppress fires from a safe distance. 

Isolation devices to preclude deflagration propagation. As noted
previously, the facilities generally did not employ any isolation
devices that would help prevent deflagrations from propagating through
ductwork from one unit operation to another. It should be noted that one
facility stated that they had considered such devices, but claimed that
such devices would not be effective due to the rate at which their
material of interest (a pyrophoric metal dust) would be expected to
react. 

Administrative Controls

ERG reviewed various types of administrative controls and work practices
that facilities implemented to control or mitigate hazards. This section
presents detailed information on housekeeping programs and procedures
(Section 9.1), given their significance in reducing the likelihood and
severity of secondary explosions, and summary information for other
administrative controls (Section 9.2) for combustible dusts. 

Housekeeping Procedures

Every facility that ERG visited had documented housekeeping and
equipment cleaning procedures to minimize accumulations of combustible
dust. One facility was part of a corporation that recently developed a
“Combustible Dust Housekeeping Guidance Document” that was
distributed to all manufacturing facilities in the company, while the
other facilities developed their own internal guidance, typically in the
form of standard operating procedures. The extent and effectiveness of
the facility-specific housekeeping procedures varied. Some general
observations about housekeeping and equipment cleaning follow: 

While all six facilities recognized the role that housekeeping plays in
minimizing combustible dust safety hazards, facilities’ housekeeping
efforts were also motivated by the need for product purity and by the
potential for customer visits. This was most evident at the
pharmaceutical manufacturer and, to a lesser extent, at the food
manufacturing facilities. Metal production facilities also had concerns
about contamination, in part because trace amounts of certain impurities
were known to compromise the performance of certain specialty products. 

The facilities implemented various types of housekeeping procedures,
which typically included routine removal of dust accumulations in
visible areas during process operations, immediate removal of localized
accumulations following process upsets, and periodic “top-to-bottom”
cleaning of entire production areas during process shutdowns or between
production campaigns. The frequency of the routine and periodic cleaning
activities varied across the facilities. 

The approaches used to remove dust accumulations were determined by the
individual materials’ hazards and properties. The most common
approaches to removing dusts included sweeping, mopping, hosing down
equipment, and vacuuming. Water wash-downs were commonplace for soluble
materials (e.g., sugars, paper dust, pharmaceuticals) but generally not
for metals. Removal of dust accumulations in Class II locations was
typically conducted using either (1) portable vacuum cleaners certified
for use in Class II locations or (2) connections to central vacuum
systems. 

Compressed air was used to remove dust accumulations at two facilities:
site visitors were told that this practice occurred only when process
operations were “shut down,” only after bulk accumulations had been
removed to the extent possible using other means, and only to remove
accumulations from crevices and other parts of operating equipment that
were difficult to reach by other means. However, in one industry, the
compressed air blow-downs were conducted a few times daily and while
process equipment was still activated and energized, and this activity
generated massive dust clouds. This practice concerned site visitors,
especially considering that operators used compressed air to remove
combustible dust from heated surfaces—a practice that could suspend
smoldering or burning material in a dusty atmosphere. The facility cited
many extenuating circumstances for why its use of compressed air was
believed to be necessary. Section 12 of this report further discusses
recommendations to OSHA regarding use of compressed air to remove
accumulations of combustible dust. 

Some facilities sought guidance from OSHA on quantitative measures for
acceptable dust accumulations. For instance, facilities wondered if
OSHA’s standard will establish objective, quantitative metrics that
facilities can use as goals for housekeeping efforts. Examples include
specifying a maximum dust thickness that is considered acceptable
(similar to the Agricultural Grain Dust standard) or a maximum allowable
mass accumulation over a given area. Section 12 presents additional
information on this issue.

At some facilities, site visitors identified inconsistent messages in
housekeeping procedures. For instance, at one facility, instructions
given in employee training differed from specifications in written
operating procedures. At other facilities, housekeeping procedures
described by safety and health personnel differed from the procedures
employees actually followed. 

Every facility had developed checklists for routine housekeeping
activities that operations and maintenance staff were instructed to
complete. The facilities also used periodic inspections to verify the
effectiveness of their housekeeping programs. 

Other Administrative Controls

Site visitors identified several other types of administrative controls
that facilities employed to control or mitigate combustible dust
hazards. Examples follow:

Personal protective equipment (PPE). All facilities required employees
in production areas to wear PPE, with the specific requirements varying
across different processes and for different reasons. Most facilities
required employees to wear hard hats, some form of safety shoes, and
protective eyewear in all production areas. Additional requirements were
observed in the food and pharmaceutical manufacturing facilities, but
primarily in the interest of product purity. Only one facility
implemented additional PPE requirements specifically to address hazards
posed by combustible dusts: a metals processing facility required its
operators to wear flame-retardant clothing, consistent with
specifications in NFPA 484 (NFPA, 2008).

Confined space entry. Every facility had a confined space entry program,
through which employees obtained permits before entering or working in
confined spaces. ERG’s observations focused on the extent to which
these programs acknowledged the unique hazards posed by combustible
dusts. At some facilities, the confined space entry program did not
allow employees to enter confined spaces if visible dust clouds were
present. One facility, for example, had procedures denying entry in
cases where dust levels impaired visibility of objects at a distance of
10 feet. Another facility established a similar condition of entry:
“…a concentration of combustible dust that obscures vision at a
distance of five feet or less.” The origin of this rule of thumb was
not known, but may be based on a previous scientific publication
(Eckhoff, 2003). 

Some facilities noted that OSHA could provide more concrete guidance on
what specific dust concentrations must be avoided for confined space
entry. These facilities noted that they have no difficulty establishing
safe guidelines for gases (e.g., oxygen levels, explosive gases) given
the availability of continuous monitoring devices and well-established
safe thresholds (e.g., lower- and upper-explosive limits), but
encouraged OSHA to develop guidance to inform facilities of similar
strategies that can be implemented for detecting and avoiding
potentially hazardous combustible dust atmospheres.

“Hot work” permits. Every facility had a “hot work” permit
program that both defined “hot work” activities and specified what
steps employees must take to obtain a “hot work” permit. Most of
these programs included general information about ensuring shutdown of
all nearby equipment before “hot work” could commence. However, one
facility specifically addressed combustible dust in their permit program
by requiring employees to “…clean built-up sugar dust from I-beams
and floors” before a permit can be issued.

Management of change. Most facilities, particularly those with processes
subject to OSHA’s PSM standard, had written management of change
procedures that outlined special requirements for managing various types
of process changes beyond replacements-in-kind. These written procedures
were fairly generic, but did set a reasonable framework for ensuring
that potential health and safety hazards are evaluated before changes
are made. During employee interviews, however, site visitors found
examples of process operators implementing changes without going through
the facilities’ written management of change procedures. 

Emergency Response

Emergency response procedures varied across the facilities. Four of the
six facilities visited had their own fire brigades, ranging in size from
15 to 75 employees. Based on limited employee interviews, fire brigade
members appeared to be well trained on the unique hazards posed by
working with the specific combustible dusts at their sites. Time
constraints prevented site visitors from conducting thorough evaluations
of the facilities’ emergency response measures, though some potential
concerns were identified. For example, at facilities where argon deluge
systems are used to suppress fires, site visitors encouraged the
facilities to ensure that first responders were equipped with oxygen
monitors to ensure that they do not become accidentally submersed in an
argon atmosphere, which can quickly overcome employees who are not
wearing suitable respiratory protection. Examples of other concerns are
noted in the individual site visit reports. 

Investigation of Incidents

At every facility, site visitors inquired about past “incidents”
involving combustible dusts. For purposes of this report, an
“incident” includes fires and explosions (regardless of the extent
of damage or injury) and near misses during which a serious fire or
explosion appeared imminent but was avoided. The individual site visit
reports document the range of incidents that occurred at the six
facilities, and the site visitors made the following general
observations pertaining to combustible dust incident investigations:

Some facilities had very detailed, written accounts of past incidents.
For example, two facilities shared spreadsheets documenting every fire
that occurred over a recent multi-year time frame. For each fire, the
spreadsheets included information on the nature and extent of the event,
possible causes, consequences, and action items; at one facility, the
spreadsheet also assigned different employees responsibility for
ensuring that recommended corrective measures were implemented.
Similarly, other facilities shared copies of hazard analyses that were
conducted, as per company policy, following specific incidents (e.g.,
fires in dryers). 

One facility relied entirely on its employees’ recollection of past
events for insights on incidents. This facility did not have a
systematic approach for identifying and investigating incidents, which
raised concern about the potential for incidents to recur in the future.


At one facility, employees frequently encountered smoldering material or
small fires that had to be extinguished—this occurred several times a
day in a particular operation. While the employees in these cases were
trained on how to control these fires and felt comfortable doing so, and
none of the fires propagated to major events according to site
representatives, site visitors were concerned about the sense of
complacency regarding a potentially hazardous occurrence (e.g., “…we
see smoldering material all the time”) and encouraged facilities to
avoid downplaying the significance of these events. 

Regulatory Approaches

At the end of every site visit, ERG asked facility representatives to
share any specific questions or concerns regarding OSHA’s combustible
dust rulemaking. While facility representatives seemed to appreciate the
need for a standard focusing specifically on combustible dust, they
relayed several concerns about the rulemaking and its potential
implications on industry: 

Applicability. Almost every facility inquired about how OSHA’s
standard will define “combustible dusts.” Some facility
representatives emphasized that hazard potential varies greatly with the
material of interest and its properties (e.g., density, moisture
content, potential for agglomerating). One facility had internal
combustible dust guidelines (see Section 6) that apply as follows: “A
dust explosion potential is considered to exist where 1 pound or more of
combustible dust per 1,000 cubic feet of volume is normally in
suspension or could be put in suspension in an enclosure or inside
pieces of equipment.” Information on the scientific basis for this
guideline was not provided. 

Retroactivity. Most facilities that hosted site visits operated
processes that were constructed more than 20 years ago and therefore
predate requirements set forth in recent editions of the NFPA standards.
These facilities wondered if OSHA’s combustible dust standard would
apply retroactively to all existing processes, regardless of their
construction date, or if it would include “grandfather” clauses for
older processes. 

Cost. Almost every facility that ERG visited had concerns about the
potential costs associated with a new combustible dust standard. Section
13 of this report provides more detail on the cost implications of a new
combustible dust standard, based on limited observations collected from
the six facilities that were visited. 

Timing. Concerned about their ability to quickly comply with a new
safety standard, especially one that might require engineering
evaluations and retrofits to processes with combustible dusts, two
facilities suggested that OSHA consider a standard with “phased-in”
compliance periods. For example, the standard might require a certain
percentage of highest priority work be completed within 1 year; another
percentage of work must be finished within 2 years; and so on. One
facility was particularly concerned about timing given their large
number of production lines (more than 10) and dust collectors that do
not fully comply with NFPA standards (more than 150). 

Limited expertise. Facilities expressed concern about having limited
internal resources and expertise to address combustible dust safety
issues, due to the highly specialized nature of the topic. Although
every facility had highly proficient on-site safety staff, not every
facility had safety personnel with a strong command of NFPA standards
and current administrative and engineering controls for addressing
combustible dust hazards. Some facilities noted that they would likely
have to hire consultants and engineering firms to implement additional
engineering controls that a new combustible dust standard may require.
Moreover, these facilities feared that the most qualified consultants
and engineering firms would not be able to handle the amount of business
that would be generated once OSHA promulgates a combustible dust safety
standard. 

Acceptable dust accumulations. Facilities had many comments about
whether the standard should include prescriptive limits for allowable
dust accumulations, whether in terms of thicknesses or area of coverage.
Some facilities expressed concern about establishing objective dust
accumulation criteria, because a given accumulation (e.g., 1/32″) can
pose dramatically different hazard potentials depending on the
material’s chemical and physical properties). While facility
representatives appreciated the scientific basis for a proposed new
approach in NFPA 654 to specify maximum allowable accumulations (i.e.,
in terms of mass per area), some people questioned the practicality of
this approach and argued that measuring an accumulation depth is far
easier than determining a mass per unit area. However, it should be
noted that the next NFPA 654 edition will likely have options for
relating accumulated mass to layer thickness, so that facilities that
want to continue using thickness measurements will have a way to do so. 

Prescriptive or performance-based. Facility representatives offered
conflicting opinions regarding the preferred format of the pending
combustible dust standard. Some representatives advocated for a highly
prescriptive standard that would leave little ambiguity about exactly
what facilities must do to comply. Other representatives supported
development of a performance-based standard (e.g., similar to the PSM
standard), which outlines general principles that facilities can then
adopt in a process-specific manner. One suggestion was to incorporate
combustible dust into the PSM standard. 

One facility offered a specific example arguing against the use of
prescriptive requirements. The facility questioned the current NFPA 654
allowance for dust collectors with volumes less than 8 cubic feet to
operate indoors. The facility found this threshold somewhat arbitrary
(e.g., would it be sufficiently protective to have a dust collector
located indoors for a highly explosive material?) and noted that the
correct limiting size of dust collector volumes is best determined by
engineering calculations and process hazard analyses. (Note: Future
versions of NFPA 654 may no longer include the size cutoff in the
requirement for dust collectors being placed outdoors; these
specifications may be replaced with a requirement for some type of
hazard or risk evaluation regarding when dust collectors can operate
indoors.) 

Material-specific requirements. Representatives from the metal
processing facilities advocated a rulemaking format consistent with
NFPA’s combustible metals standard (NFPA, 2008), which presents
separate requirements for different metals (e.g., aluminum, magnesium,
titanium). These individuals explained that having material-specific
requirements greatly simplified compliance, because the facilities only
needed to focus on certain sections of the standard. They also supported
this approach given that the combustion and explosion properties vary
considerably from one metal to the next. However, recognizing the broad
range of materials (and mixtures) that OSHA’s combustible dust
standard might address, these facility representatives also acknowledged
that including material-specific requirements might not be feasible.

Consistency with other standards. Some facilities voiced concern about
having to understand and comply with multiple consensus and regulatory
standards all pertaining to combustible dust (e.g., NFPA standards,
insurance guidelines, OSHA regulations). One suggested approach for
alleviating this situation was for OSHA to consider the use of multiple
compliance options in its combustible dust standard, with one option
being strict compliance with all applicable NFPA standards. By this
approach, facilities that already have invested considerable resources
to meet applicable NFPA standards would not have to invest additional
resources to evaluate the specific requirements in OSHA’s pending
rulemaking. This commenter acknowledged, however, that simply
referencing the NFPA standards would also present compliance and
enforcement obstacles, given that these standards can change with every
new edition issued. 

Streamlining requirements of multiple agencies. Facilities in industries
regulated by multiple entities (e.g., the Food and Drug Administration)
expressed concern about OSHA’s upcoming combustible dust standard
conflicting with requirements under other statutes. 

Other concerns about restrictive standards. Given the many different
industry-specific nuances associated with controlling dust hazards, many
facilities expressed concern about OSHA developing a standard with
overly restrictive requirements. For instance, one facility feared that
OSHA’s combustible dust standard would prevent the use of compressed
air to remove dust accumulations or would severely limit its use (e.g.,
limiting the air pressures allowed). This facility argued that the
practice not only was commonplace throughout this industry, but was also
the only feasible approach to removing settled dusts from crevices and
other inaccessible areas in large production equipment. As another
example, multiple facilities expressed concern about OSHA possibly
requiring all dust collectors larger than a certain volume to be placed
outside, as is outlined in some NFPA standards. One facility
representative noted that, in certain scenarios, dust collectors may be
operated safely within buildings. For example, he explained that wet
dust collectors are inherently safer than dry dust collectors, because
they capture and extinguish any ember or spark entrained in dust-laden
process air streams; facilities also expressed concern about the
economic impacts of being required to reconfigure processes to move dust
collectors outdoors (see Section 13). 

Economic Impacts and Benefits

While this project was not designed to provide detailed economic
analyses of combustible dust control options, site visitors were
provided with costs associated with implementing various combustible
dust control measures at several of the facilities visited. A summary of
relevant observations made during the site visits follows: 

Costs of complying with NFPA standards. One facility had previously
conducted an internal assessment of the estimated costs to bring the
entire facility into compliance with NFPA standards pertaining to
combustible dust. This facility, which operated more than 160 dust
collectors (most of which had no explosion protection features),
estimated that the up-front costs for upgrading these operations would
range from $10 million to $28 million. These costs focused exclusively
on retrofit activities for dust collectors, and did not consider costs
for upgrading other devices that may be regulated under a new
combustible dust standard (e.g., dryers, mixers, commodity bins). These
projected costs also do not reflect a variety of additional costs that
the facility might incur due to a new combustible dust standard.
Examples of such additional costs include those associated with
conducting hazard analyses, developing and implementing specialized
training, and testing of new materials.

Industry-specific considerations. When conducting its regulatory impact
analysis, facilities encouraged OSHA to consider several factors that
may be unique to certain industries. For example, some industries rely
upon production technologies (e.g., electron beam furnaces in metals
production, large paper machines at paper mills) that cost more than
$200 million to purchase and install; representatives from these
industries said they would bear unusually high costs to replace such
operations or retrofit them with dust controls. As another example,
equipment replacement costs can vary greatly due to required materials
of construction; this is of particular concern in the food and
pharmaceutical manufacturing facilities, which must use materials that
do not introduce contaminants into their products. Finally, compliance
with NFPA standards has cost implications that vary across industries:
for instance, NFPA 484 does not allow for titanium manufacturing
facilities to operate dry dust collectors inside buildings, and these
facilities would either have to reconfigure their processes to move
devices outdoors or install different controls to comply with the
standard; however, food manufacturing facilities can leave such devices
indoors and still meet NFPA 61 requirements, though certain design
criteria must be met.

Consideration of up-front and ongoing costs. Regarding OSHA’s economic
analyses for the combustible dust standard, facilities noted that
compliance costs are not limited to up-front capital investments for
purchasing new fire and explosion equipment, but also include costs
associated with engineering and design evaluations, installation, and
ongoing operations and maintenance. In some cases, these other costs
outweigh the costs of purchasing new equipment. For instance, one
facility provided itemized costs for installing a new wet dust
collection system at a metal saw operation: the dust collector itself
reportedly cost $15,000, but the facility spent an additional $45,000 on
ductwork and installation costs. To provide insights on ongoing
maintenance costs, a facility noted that they pay approximately $8,000 a
year to have employees attend training courses on inspection and
maintenance of explosion suppression systems.

Detailed cost information obtained during site visits. Several
facilities provided site visitors information on the costs of various
activities associated with combustible dust safety programs. For some
combustible dust control measures, facilities made records available
that clearly documented associated costs; but in other cases, facilities
only estimated what they had paid. Most cost data provided by the
facilities was dated any time between the late 1990s and the present. 

Attachment 1 to this report lists laboratory analytical costs that two
facilities shared for different types of testing. As the table shows,
these costs can vary significantly from one laboratory to the next. It
is possible that some quotes shown in the table represent discounted
costs due to the large number of samples that certain facilities had
analyzed. Moreover, in cases where combustible dusts are extremely
valuable materials (particularly for pharmaceuticals), the value of the
material “lost” in collecting a 1-liter sample can exceed the
laboratory analytical costs shown in Attachment 1. 

According to the one facility that used oscillating ceiling fans to
prevent dust accumulations on overhead structures, the cost to purchase
and install the fans was approximately $8,000 per fan, though the
facility expected this cost to decrease when purchasing large numbers of
these controls. Costs associated with operating the fans were not
available. Note that the facility believed the purchase and operation
costs for the fans may have been less than the costs of having two
employees work full-time vacuuming dust accumulations from overhead
structures throughout the production building. The oscillating fans were
also preferred given the potential safety hazards associated with
employees operating vacuum cleaners while on scissor lifts.

Costs for installing new dust collectors can vary widely, depending upon
design specifications. One facility noted that it cost approximately
$60,000 to purchase and install a “small” dust collector dedicated
to a band saw operation. On the other hand, a facility stated that the
overall cost of replacing a dry dust collector with a wet scrubber
designed to control 26,500 cubic feet per minute air flow of a
dust-laden process stream was approximately $550,000.

As stated earlier, the previous information should be viewed only as a
small collection of observations regarding costs of implementing
combustible dust control strategies. A more extensive review would be
needed to more fully evaluate the potential range of costs for
identifying and mitigating combustible dust hazards. 

Impacts on Small Entities

This project considered an opportunistic sample of industrial
facilities. Meaning, for the industries of interest identified by OSHA,
ERG visited the first facilities that expressed interest in
participating. While inferences can be made from information in this
report on potential impacts to small entities (e.g., limited in-house
health and safety resources, likelihood of not having their own fire
brigades), this project was not designed to characterize potential
impacts of a combustible dust rulemaking on small entities. Every
facility visited during this project had at least 80 employees.

Compliance Assistance

All six industrial facilities that ERG visited provided feedback on the
compliance assistance resources they have accessed for information on
combustible dust and the quality of technical support offered by those
resources. A summary of this information follows: 

When asked about the possibility of a new combustible dust standard,
some facility representatives recommended that OSHA place lesser
emphasis on regulation and enforcement, and greater emphasis on
guidance, compliance assistance, and other proactive measures to help
facilities identify and implement best practices for controlling
combustible dust hazards. One suggestion was for OSHA technical staff to
work with facilities in more of a cooperative and consultative manner
(e.g., through voluntary site visit programs), rather than interact with
facilities largely through inspections. Another suggestion was for OSHA
to develop industry- or material-specific guidance on combustible dust
safety issues, similar to U.S. Environmental Protection Agency guidance
for Risk Management Plan requirements (see:   HYPERLINK
"http://www.epa.gov/emergencies/guidance.htm#rmp" 
http://www.epa.gov/emergencies/guidance.htm#rmp ). 

Facilities’ awareness of OSHA publications on combustible dust also
varied. On one hand, some facility representatives were aware of the
National Emphasis Program, had read various OSHA documents on
combustible dust posted to the agency’s Web site
(http://www.osha.gov/dsg/combustibledust), and had attended OSHA-hosted
seminars on combustible dust safety issues. Other facility
representatives were not aware of these and other OSHA resources. Some
facilities subscribed to regulatory summary services, which informed
designated facility contacts of ongoing activity pertaining to safety
and health, environmental, food safety, and other applicable
regulations. 

The facilities also had differing experiences with personal interactions
with OSHA on combustible dust safety issues. Representatives from one
facility commented that state OSHA officials seemed relatively
experienced with agricultural dusts, but had limited expertise with
combustible metals. 

Site visitors asked facility representatives to identify other potential
sources of compliance assistance information, beyond those listed in
above. Not every facility tapped into these other sources, and those
cited as being most informative were: a combustible dust course offered
by a state Safety Council, an NFPA-sponsored conference on combustible
dust, and a facility-sponsored symposium on combustible dust hazards
posed by a unique material.

Facility representatives specified several topics for which technical
guidance would be beneficial. As Section 2 notes, facility
representatives had numerous technical questions about how best to use
laboratory analyses and other methodologies to characterize their
materials. They encouraged OSHA to issue guidance on testing (e.g.,
which materials to test, what methods to use, how to interpret results).
Further, the facilities requested clarification from OSHA on exactly
what parameters suppliers are expected to include on MSDSs versus what
parameters facilities would be expected to determine on their own. 

Many different compliance assistance resources are currently available
on combustible dusts and their associated hazards, but the resources are
not always consistent. Facilities noted the need to have a single
resource of trusted information that they can access to ensure
compliance with OSHA’s upcoming standard. 

References

Barbauskas, 2003. Ignition Handbook. Vytenis Babrauskas. Fire Science
Publishers: Issaquah, WA.

Bartnecht, 1981. Explosions, Course, Prevention, Protection. W.
Bartnecht. Springer-Verlag: New York, NY. 

Eckhoff, 2003. Dust Explosions in the Process Industries (3rd Edition).
R.K. Eckhoff. Gulf Professional Publishing, Elsevier Science:
Burlington, MA. 

ERG, 2008. Site Visits Related to Combustible Dust: Project Protocol.
Prepared by Eastern Research Group, Inc. Prepared for OSHA Directorate
of Standards and Guidance. December 12, 2008. 

FM, 2009. FM (Factory Mutual) Global Data Sheet 7-76: Prevention and
Mitigation of Combustible Dust Explosion and Fire. March, 2009.

NFPA, 2008. NFPA 484: Standard for Combustible Metals. 2009 Edition.
National Fire Protection Association. October 10, 2008.

OSHA, 2009a. U.S. Department of Labor’s OSHA announces rulemaking on
combustible dust hazards. U.S. Department of Labor, OSHA, Office of
Communications. National News Release: 09-475-NAT. April 29, 2009. 

OSHA, 2009b. Advanced Notice of Proposed Rulemaking for Combustible
Dusts. Federal Register, 74(202):54334-54347. October 21, 2009. 

OSHA, 2009c. Hazard Communication Guidance for Combustible Dusts. OSHA
3371-08. 2009.
< http://www.osha.gov/Publications/3371combustible-dust.html >

Attachment 1: Laboratory Analytical Cost Data Provided by Selected
Facilities

Multiple facilities informed site visitors of the prices commercial
laboratories charge for analyzing samples for explosibility parameters.
In most cases, however, the information provided was either incomplete
or did not itemize costs by the specific analyses conducted. The
following table provides the only itemized costs that ERG received, and
these costs are based on recent testing quotes provided by two different
commercial analytical laboratories. 

Reported Laboratory Costs for Analyzing One Sample

Test Parameter	Analytical Method	Analytical Costs



Laboratory #1	Laboratory #2

Minimum explosible concentration	ASTM E 1515	$520	$1,495

Minimum ignition energy	ASTM E 2019	$695	No data

Full particle size distribution	ASTM D 1921	$220	No data

Minimum auto-ignition temperature of dust clouds	ASTM E 1491	$680	$1,150

Explosion severity test (Pmax and Kst)	ASTM E 1266	$1,000	$2,095

Limiting oxidant concentration	Not specified	$1,200	No data



Note: 	These laboratories also had supplemental charges for their
analyses not specified here. Additionally, the above costs are based on
analyses of a single sample. These laboratories offered their customers
volume discounts for having multiple samples analyzed. It is possible
that the costs quoted for “Laboratory #1” are biased low, because
the facility that provided these costs is a frequent customer of the
laboratory and therefore might be offered more competitive rates.

 Two visits were conducted before April 29, 2009, when OSHA publicly
announced its intention of developing a new combustible dust standard
(OSHA, 2009a), and four visits were conducted after this announcement.
Further, five visits were conducted before October 21, 2009, when OSHA
published it’s Advanced Notice of Proposed Rulemaking (ANPR), and one
visit was conducted after the ANPR was issued.

 The number of employees mentioned in this sentence only includes those
that were identified as having formal health and safety
responsibilities. These tallies do not include facility or process
engineers whose primary job responsibility is not health and safety, but
nonetheless contribute to the facility’s overall health and safety
programs. 

 The issue of analytical methods was raised at multiple site visits.
Specific concerns included the fact that OSHA’s laboratory does not
use ASTM methods when measuring Kst values and that facilities were
unaware of any standard methods for measuring “settled bulk density”
of dusts—a parameter used in NFPA 654 to calculate allowable
thicknesses of dust accumulations. 

 Facilities did not provide a list of references they considered when
seeking previously reported analytical data. One facility was part of a
corporation with a centralized laboratory that analyzed hundreds of
samples from multiple facilities. Facilities within this corporation had
access to the entire history of testing results. 

 The applicable NFPA standards in these cases allow for dust
collectors’ clean air exhaust to be returned into the workplace, but
only when “tests conducted by an approved testing organization prove
the collector’s efficiency is great enough to provide both personnel
and property safety in the particular installation…” and when the
design prevents fire or explosion transmission back into the building;
most facilities that operated these dust collectors apparently did not
conduct such evaluations.

 The two facilities that did not have fire brigades were the facilities
that had the fewest employees. 

 This facility indicated that they are one of the smaller facilities in
their particular industry and suspected that other facilities will
likely face even greater obstacles in rapidly coming into compliance
with a new standard. 

 One facility indicated that allowable dust accumulations for lighter
materials (e.g., paper dust) can be greater than 1 inch based on the
density correction factors currently in NFPA 654’s equations for
allowable dust accumulation thicknesses. The facility noted that, for
extremely light substances (e.g., those with density less than 1
lb/ft3), the NFPA 654 equations allow dust accumulations greater than
2.3 inches. This facility also questioned why the equations do not
include corrections for moisture content: in the current equation,
increased moisture content will increase the density and therefore
decrease the allowable accumulation thickness, even though wet dusts are
more difficult to disperse in air and ignite.

 Although this facility was the largest that ERG visited, in terms of
number processes and dust collectors, this facility’s representatives
noted that their facility is relatively small for their industry.
Facility representatives suspected that other facilities in this
industry would face far greater costs associated with upgrading their
processes to be fully compliant with applicable NFPA standards.

 The next edition of NFPA 484 will allow at least some dry dust
collectors at metals manufacturing facilities to be installed indoors,
provided the dust collectors are equipped with the specified explosion
protection. 

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increase to increase the scrubber capacity to 53,100 cubic feet per
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and return it to the workplace during the winter months; $36,000 in
freight charges; and $5,000 in other charges. 

 PAGE   

 Synthesis Report 

 PAGE   3 

Draft Synthesis Report 

 

