
[Federal Register Volume 77, Number 72 (Friday, April 13, 2012)]
[Notices]
[Pages 22381-22383]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-8970]


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DEPARTMENT OF TRANSPORTATION

Federal Railroad Administration

[Safety Advisory 2012-01]


Odorant Fade in Railroad Tank Cars

AGENCY: Federal Railroad Administration (FRA), Department of 
Transportation (DOT).

ACTION: Notice of Safety Advisory.

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SUMMARY: FRA is issuing Safety Advisory 2012-01 to remind shippers and 
consignees of railroad tank cars containing odorized liquefied 
petroleum gas (LPG), of the importance of taking actions to ensure that 
a sufficient level of odorant remains in the LPG throughout the entire 
transportation cycle. FRA is issuing this notice to raise awareness 
within the hazardous materials community, of the potential consequences 
of having LPG reach end-users as under-odorized or essentially non-
odorized material due to the diminishment of the added odorant during 
the transportation cycle (commonly known as ``odorant fade''). This 
safety advisory recommends that shippers and consignees of bulk 
quantities of odorized LPG review their existing LPG odorization 
standards and procedures, and take appropriate actions to guard against 
odorant fade in their shipments.

FOR FURTHER INFORMATION CONTACT: Kevin R. Blackwell, Railroad Safety 
Specialist, Hazardous Materials Division, Office of Safety Assurance 
and Compliance, FRA, 1200 New Jersey Avenue SE., Washington, DC 20590 
(telephone: (202) 493-6315; email: Kevin.Blackwell@dot.gov); or Kurt 
Eichenlaub, Railroad Safety Specialist, Hazardous Materials Division, 
Office of Safety Assurance and Compliance, FRA, 1200 New Jersey Avenue 
SE., Washington, DC 20590 (telephone: (202) 493-6050; email: 
Kurt.Eichenlaub@dot.gov).

SUPPLEMENTARY INFORMATION: DOT's Hazardous Materials Regulations (HMR), 
Title 49 Code of Federal Regulations (CFR) Parts 171-180, allow use of 
the proper shipping name, ``liquefied petroleum gas'' (or LPG), for a 
number of petroleum gases with properties similar to propane. Much of 
the LPG loaded and shipped in the United States by railroad tank car is 
from bulk suppliers to either industrial end-users or to ``midstream'' 
suppliers who then sell and redistribute the LPG to commercial, retail, 
and general public end-users. In 2010, LPG represented less than 9 
percent of all loaded hazardous materials tank car shipments 
originating in the United States. Because LPG is a colorless and 
odorless gas, odorants are normally added to the material (with the 
exception of LPG being shipped to industrial end-users) in the liquid 
phase to enable human detection when its vaporized gases are released 
in the atmosphere. The majority of LPG produced for non-industrial uses 
is odorized by bulk providers of the material. The presence of LPG in 
the consumer supply chain, with either diminished levels of odorant or 
no odorant present, represents significant safety risks. Absent 
sufficient odorization of the commodity, LPG leaks can go undetected 
and ignite.
    Diminished or absent levels of LPG odorant has been determined to 
have been a contributing factor in incidents that have resulted in 
injuries and fatalities. For example, a July 30, 2010, incident 
occurred at a condominium construction site in Norfolk, MA, when a 
release of LPG from a leaking connection in the basement of a building 
under construction resulted in an explosion and fire. This incident 
resulted in one fatality and seven injuries. An investigation conducted 
by the Massachusetts Department of Fire Services, Division of Fire 
Safety, revealed that the LPG in the storage tanks at the construction 
site had virtually no odorant present, explaining why no one at the 
construction site reported smelling the LPG leak prior to the 
explosion. While the LPG involved in the Norfolk accident did not 
originate from a rail shipment, the investigation into the accident 
revealed that a large quantity of LPG--shipped via railroad tank car as 
odorized--had been delivered to commercial and retail end-users with 
either a diminished level of odorization or no odorization at all.

Odorization

    The proper odorization of LPG is addressed by a combination of 
Federal and State laws and regulations, as well as by accepted industry 
standards and practices. In accordance with the applicable laws and 
regulations, LPG intended for use by non-industrial entities (e.g., 
commercial and retail entities, and the general public) is generally 
required to be odorized (or ``stenched'') to enable the detection of 
any unintended release or leak of the gas. In the context of the rail 
transportation of LPG, the HMR require the odorization of LPG 
transported in cargo tanks and portable tanks, but not railroad tank 
cars. Specifically, 49 CFR 173.315(b)(1) provides that odorizing LPG 
shipments in cargo and portable tanks with 1.0 pound of ethyl mercaptan 
per 10,000 gallons of LPG, or the equivalent, is an acceptable form of 
odorization.\1\ That section also provides an exception from the 
odorization requirement if odorization would be ``harmful in the use or 
further processing of the [LPG], or if odorization will serve no useful 
purpose as a

[[Page 22382]]

warning agent in such use or further processing.'' Essentially, this 
exception applies to LPG being transported to industrial end-users.
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    \1\ Ethyl mercaptan is a colorless organic liquid with a low 
odor threshold of 0.4 parts per billion, thus making it easily 
detectable by persons with a normal sense of smell when injected at 
standard industry rates.
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    The Occupational Safety and Health Administration's requirements 
regarding the storage and handling of LPG found at 29 CFR 
1910.110(b)(1) essentially mirror DOT's odorization requirements at 49 
CFR 173.315(b)(1). In addition to these Federal regulations, the 
National Fire Protection Association (NFPA) has also established 
odorization standards that largely mirror the Federal requirements. See 
NFPA Standard 58, paragraph 1-4.1. In addition, most States have 
adopted laws, regulations, or codes that incorporate this NFPA 
standard. Further, it is standard industry practice to exceed the 
established regulatory minimums and add 1.5 pounds of ethyl mercaptan 
per 10,000 gallons of LPG in order to combat the effects of odorant 
fade should a release of material occur.

Odorant Fade

    Under-odorization of railroad tank cars containing LPG is sometimes 
caused by the phenomenon commonly known as odorant fade. While LPG may 
be satisfactorily odorized in accordance with the above requirements at 
the source, there are circumstances that may cause the odorant added to 
the LPG to ``fade'' and render it virtually undetectable by a person's 
sense of smell. Typically, there are three different potential causes 
of odorant fade: oxidation, container condition, and gas quality.
    This safety advisory focuses on recommendations to prevent odorant 
fade caused by oxidation and/or the condition of the LPG container. 
First, oxidation can cause odorant fade when the presence of rust in a 
tank car, or the subsequent formation of rust over time, as a result of 
the presence of oxygen and moisture, decreases the amount of odorant 
that is in the LPG in the tank due to a chemical reaction between the 
odorant and the oxidized (rusted) surface. The presence of rust causes 
mercaptans to oxidize into other compounds that have a different odor 
and lower intensity. Residual oxygen from air and moisture that may be 
in the container can increase the oxidation rate of rust or even cause 
new rust to form where previously none existed, exasperating the rate 
at which the odorant fades.
    Next, the condition of the LPG container itself can also 
potentially cause odorant fade. An odorant can adsorb onto the metal 
surface of the container or even potentially be absorbed into the metal 
surface itself. This process is most likely to occur when the container 
is new and has not previously contained odorized LPG. It can also occur 
when the inside of the container has been left open to the air while 
the container is out of service or after the container has been cleaned 
and purged (e.g., when a railroad tank car is cleaned and purged for 
repair or service at a tank car facility and then later placed back 
into LPG service).
    There are existing industry procedures that can passivate (or 
treat) the interior surface of an LPG container in order to render the 
surface inactive so that the odorant will not be diminished through 
oxidation or adsorption/absorption. Also, there are several methods 
available to detect whether there are adequate amounts of odorant in 
LPG at any given point. The simplest, and most often used method, is a 
``sniff test'' where a person uses their sense of smell to detect the 
presence of odorant. The person performing a sniff test should have a 
normal sense of smell, uncompromised by such factors as olfactory 
fatigue, sinus congestion, allergies, head colds, smoking, or the 
recent use of alcohol or drugs. Colorimetric tube testing and the gas 
chromatography test method provide more quantitative methods to measure 
the concentration of the odorant in LPG. The colorimetric tube, or 
stain tube, test method measures the concentration of odorant by 
pulling a measured amount of LPG through a hermetically sealed glass 
tube containing a detecting reagent. The odorant causes a chemical 
reaction resulting in a color change of the tube material. The quantity 
of odorant can be measured by reading the concentration of the odorant 
from the calibration scale that is marked on the tube. The gas 
chromatography test method is the most accurate method because it 
separates the various components of the LPG and odorant for 
identification. However, this method is costly and requires sending LPG 
samples to a location that has the proper equipment and trained 
personnel to perform these tests.

Railroad Tank Cars

    At present, while DOT's regulation discussed above contains an 
odorization requirement for LPG transported in cargo and portable tank 
containers, there is no comparable DOT regulation regarding the 
transportation of LPG transported in railroad tank cars. FRA is 
currently reviewing this situation to determine if further action is 
warranted. During routine inspections at facilities that receive 
railroad tank cars loaded with LPG, FRA is obtaining data on the LPG 
odorization testing procedures being used by industry. FRA is also 
collecting data on the number of LPG shipments that are received 
yearly, the number of these shipments that are shipped as odorized 
versus non-odorized, and the number of odorized shipments received that 
failed odorization testing or were identified as having insufficient 
odorant.
    As noted above, there are currently Federal regulations, State 
laws, and accepted industry standards and testing methods in place to 
ensure proper LPG odorization. FRA encourages industry members to 
comply with all applicable requirements and standards. In order to help 
prevent odorant fade incidents involving LPG transported by railroad 
tank car, and to facilitate compliance with existing requirements and 
standards, this safety advisory makes several recommendations below.
    Recommended Action: In an effort to encourage industry members to 
take actions to ensure that a sufficient level of odorant remains in 
odorized LPG shipped via railroad tank car throughout the entire 
transportation cycle, FRA recommends that:
    1. Facilities that load, offer, receive, or offload railroad tank 
cars containing LPG review their procedures to ensure they are adequate 
to address the issue of ``odorant fade'' and its various potential 
causes, and that those procedures ensure that tank car shipments of 
odorized LPG are odorized to meet applicable regulatory and industry 
requirements and maintain sufficient levels of odorant throughout the 
entire transportation cycle. Such procedures should ensure quantitative 
testing methods are used to measure the amount of odorant in LPG.
    2. Facilities that load odorized LPG into railroad tank cars have 
adequate procedures in place to identify if a tank car received for 
loading of odorized LPG has been out of LPG product service for any 
extended length of time, is coming from a tank car repair or cleaning 
facility, or has been subjected to any condition that could lead to 
corrosion of the tank.
    3. Facilities that load odorized LPG into railroad tank cars 
inspect, to the degree possible, railcars they receive for signs of 
oxidation or corrosion, which can lead to the loss of odorant.
    4. Facilities that load odorized LPG into tank cars take any other 
corrective actions needed to ensure sufficient levels of odorization 
remain in the shipment throughout the entire transportation cycle, such 
as increasing the amount of odorant injected into the LPG, if 
necessary.
    FRA encourages industry members to take actions consistent with the

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preceding recommendations, and to take other complementary actions to 
help ensure the safety of the Nation's citizens and railroads. FRA may 
modify this Safety Advisory 2012-01, issue additional safety 
advisories, or take other appropriate actions necessary to ensure the 
highest level of safety on the Nation's railroads, including pursuing 
other corrective measures under its regulatory authority.

    Issued in Washington, DC, on April 9, 2012.
Robert C. Lauby,
Acting Associate Administrator for Railroad Safety/Chief Safety 
Officer.
[FR Doc. 2012-8970 Filed 4-12-12; 8:45 am]
BILLING CODE 4910-06-P


