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Summary of 87 Masonry Heater Emissions Tests

Norbert Senf

Masonry Stove Builders

25 Brouse Road, RR 5

Shawville, Québec  J0X 2Y0

(819)647 5092

  HYPERLINK "mailto:mheat@heatkit.com"  mheat@heatkit.com 

  HYPERLINK "http://www.heatkit.com"  www.heatkit.com 

Summary of 14 Masonry Heater Emissions Tests

Alex Chernov

STOVEMASTER

20655 Shaws Creek Rd

Caledon, Ontario L7K 1L7

 HYPERLINK "mailto:alex_stovemaster@yahoo.ca" alex_stovemaster@yahoo.ca 

  HYPERLINK "http://www.stovemaster.com"  www.stovemaster.com 

July 10, 2010



Table of Contents

  TOC \o "1-3" \h \z \u  

  HYPERLINK \l "_Toc266436197"  1.)    Executive Summary	  PAGEREF
_Toc266436197 \h  3  

  HYPERLINK \l "_Toc266436198"  2.)	Summary of 87 Masonry Heater
Emissions Tests	  PAGEREF _Toc266436198 \h  4  

  HYPERLINK \l "_Toc266436199"  Introduction	  PAGEREF _Toc266436199 \h 
4  

  HYPERLINK \l "_Toc266436200"  Calibration and Accuracy	  PAGEREF
_Toc266436200 \h  4  

  HYPERLINK \l "_Toc266436201"  Notes on the Condar Method	  PAGEREF
_Toc266436201 \h  5  

  HYPERLINK \l "_Toc266436202"  Test Results	  PAGEREF _Toc266436202 \h 
8  

  HYPERLINK \l "_Toc266436203"  3.)	Summary of 14 Masonry Heater
Emissions Tests	  PAGEREF _Toc266436203 \h  13  

  HYPERLINK \l "_Toc266436204"  Introduction	  PAGEREF _Toc266436204 \h 
13  

  HYPERLINK \l "_Toc266436205"  Calibration and Accuracy	  PAGEREF
_Toc266436205 \h  13  

  HYPERLINK \l "_Toc266436206"  Test Results	  PAGEREF _Toc266436206 \h 
14  

  HYPERLINK \l "_Toc266436207"  4.) Discussion	  PAGEREF _Toc266436207
\h  16  

  HYPERLINK \l "_Toc266436208"  References	  PAGEREF _Toc266436208 \h 
17  

 



Executive Summary

This report summarizes PM emissions testing on 3 masonry heaters, using
Oregon Method 41 (OM-41, or Condar method). 

 Data from OMNI-Test is provided, comparing OM-41 with ASTM  E25215-09.

The average PM emissions factor for 103 tests was 1.27 g/kg. The range
was 0.48 – 4.61 g/kg over a wide range of operating and fueling
conditions, which are discussed.

PM emissions rates during the short burn cycles were in the range of 7.5
- 54.7 g/hr. They are not directly comparable to the emissions factors
for reasons that are discussed. Additional data is presented comparing
emissions factors and emission rates as tested in Fairbanks, Alaska for
3 categories of appliances.

Summary of 87 Masonry Heater Emissions Tests

Norbert Senf

Masonry Stove Builders

25 Brouse Road, RR 5

Shawville, Québec  J0X 2Y0

(819)647 5092

  HYPERLINK "mailto:mheat@heatkit.com"  mheat@heatkit.com 

www.heatkit.com

Introduction

A series of 87 test runs was performed on a single masonry heater,
between 2008 and 2010. The HeatKit model heater is typical of the
majority of heaters being built in North America today, with a
Contraflow design and a large firebox designed to handle a wood charge
of 60 lbs.

Particulate emissions were sampled using Oregon Method 41 (OM-41 or
Condar Method), which uses a portable emissions sampler that
incorporates dilution.

A wide variety of operating parameters was tested, as follows:

Cordwood of various sizes, species and moisture contents. The majority
of tests were conducted with white birch at 20% moisture content, with
the bark left on and only loose bark removed. 

Fuel charges varied from 59% to 203% of the 60 lb design load.

Lumber fuel cribs of various configurations, including high and low
moisture and several loading factors and ignition methods.

Various ignition methods, such as bottom, side and top kindling.

Cold and warm fireboxes.

Calibration and Accuracy

This was a low budget study done for in-house research purposes.
Calibration gases were not used. 6” glass filters were used in the
Condar sampler. Filter dessication was not used, since it was determined
by testing that it did not make any appreciable difference.

To allow comparability between tests and avoid inaccuracy, the following
methods were used:

A model Testo 330-2 commercial combustion analyzer, which is widely used
in Europe. It has an auto-calibration routine and self-diagnostics for
leaks, worn chemical cells, etc. Manufacturer’s stated accuracy for O2
is +/-0.2 Vol.%

Extra run time for the combustion analyzer before and after a test to
quantify any drift in the ambient (span) O2 value.

The identical blank filter was weighed before and after each run, to
detect drift in the calibration of the analytical balance, or moisture
or static issues.

Testing to determine that use of a dessicator for the 6” glass filters
did not affect results significantly.

Notes on the Condar Method

The main critique of the Condar method has been that it is a constant
flow sampling method, as opposed to proportional flow in M-5H. There are
some data to suggest that Condar results can still be useful,
particularly for comparison testing of low emissions appliances with a
well defined and repeatable burn cycle.

There are two data points from OMNI-Test from July, 2006 tests on a
Swedish masonry heater, comparing PM emission using Condar, ASTM and ESS
methods as follows:

Table   SEQ Table \* ARABIC  1 

OMNI-Test Results

Run	Fuel Moisture (dry basis)	Fuel Weight (dry kg)	Test Length

(hours)	Burn Rate

(dry kg/hr)	Emissions Factor (g/kg)

ASTM	Emissions Rate 

(g/hr) 

ASTM	Emissions Factor (g/kg)

ESS	Emissions Factor (g/kg)

Condar	Emissions Rate (g/kg)

Condar	Fuel Type

4	10.9	19.0	4.7	4.1	2.7	11.07	2	2.5	10.25	Cordwood

5	20.9	18.0	6.0	3.0	2.7	8.1	2	2.5	7.5	Dimen-sional

		

There was also a study on pellet stoves conducted in New Zealand in 2005
(Reference 1). A Condar sampler was used to conduct in-home field
testing. As part of the study, comparison testing was done between the
Condar and method AS/NZS 4012/3, which is a laboratory dilution tunnel
method. The correlation was very good, as shown in Figure 1, below.

Figure   SEQ Figure \* ARABIC  1 

The Condar sampler used for our testing was part of a study conducted in
2007 at Cold Climate Housing Research Center in Alaska (Reference 2).
Four samplers were run on the same heater. The filter catches between
separate samplers were plus or minus 10%, as shown in Figure 2, below. 

Figure   SEQ Figure \* ARABIC  2 . Four Condars sampling the same stove.

Masonry heaters burn in the same 1 g/kg PM range as pellet stoves. The
filter catch is mainly soot, with little or no tar. This can be verified
by a “smell test” on the filters. With only soot on the filters
there is no smell, whereas the aromatics in woodsmoke are detectible by
the human nose even at low concentrations.

Soot is produced from flames, whereas tar is produced from smoldering
(flameless) combustion. In theory, this may allow for simplified
sampling trains for low emissions, non-smoldering appliances such as
masonry heaters and pellet stoves.

Test Results 

A summary of test results is presented in Table 2.

Average PM factor for 87 tests was 1.29 g/kg.

If we look only at “normal” conditions by eliminating cold starts,
bottom ignition and cribs, the average PM Factor was 0.97 g/kg for 52
cordwood tests in a conditioned heater.

The two largest separately observed operating variables leading to
significantly higher PM emissions were cold start and bottom ignition.
However, the combination of cold start with bottom ignition was
relatively clean. This may be due to their opposing effects on burn
rate.

For bottom ignition in a cold heater, average PM factor was 1.31 g/kg
for 5 tests. With bottom ignition in a warm heater, 1 cordwood test
yielded 3.25 g/kg and 1 crib test yielded 3.63 g/kg. 

The highest PM factor recorded was 4.6 g/kg, using cold white birch
cordwood in a cold heater with no chimney draft and a resulting slow,
smoldering start.

The higherst PM factor in a crib test was 3.61 g/kg, with a large, very
dry crib at 10% moisture in a warm heater, with a kindling crib stacked
underneath. A repeat run with the kindling crib stacked on top resulted
in 1.06 g/kg. This demonstrates the effect that ignition method can have
in cold-to-cold testing.

The average PM factor for 16 crib tests was 1.79 g/kg.

The 52 “normal” runs, averaging 0.97 g/kg, had an average burn rate
of 12.2 kg/hr and an average PM emissions rate of 11.81 g/hr. See
“Discussion” section for a comparison of emissions rate and
emissions factor for a masonry heaters and an EPA stove.

More detailed results, including raw data and detailed fueling data, are
available online at 

  HYPERLINK "http://heatkit.com/html/lopez.htm" 
heatkit.com/html/lopez.htm 

Also available online are various summary pages, such as crib
repeatability testing.

Calculations for the Condar Method were done according to Reference 3.
The calculation spreadsheet is available online.

The column headings in Table 2 (next page) are as follows:

PM g/kg: particulate emissions factor as determined by Oregon  Method 
41 (OM-41 or Condar method)

CO emissions factor, using OM-41

Eff: Overall efficiency, using OM-41

Moisture: Wood  moisture, % dry basis

Load : fuel load in lbs. Tests were single load with the following
exceptions:

L02 and L06 – L15 were reloads (2 loads)

Pieces #: Total number of fuel pieces

Sizing: some tests included a surface/volume factor for the fuel pieces

Kindl: weight of kindling in lbs (included in total fuel load)

Cold or warm heater/fuel: CC means cold heater and cold fuel, whereas WW
means warm heater (fired 24 hrs previously) and room termperaturefuel.

Ignition/stacking: default is log cabin stacking with kindling from the
side. Notes if kindling was underneath, fuel was stacked front-to-back,
or if crib fuel was used. Grate was left open for all tests except K01
– K05, where it was accidentally left closed.

The last (unlabelled) column has additional fuel notes, such as
species.Table   SEQ Table \* ARABIC  2 . DATA SUMMARY --Particulates,
Carbon Monoxide and Efficiency for 87 contraflow heater tests

Key:

PM factors less than 1 g/kg are highlighted in green

PM factors between 1 – 2 g/kg are in white

PM factors greater than 2 g/kg are highlighted in brown

 

Summary of 14 Masonry Heater Emissions Tests

Alex Chernov

STOVEMASTER

20655 Shaws Creek Rd

Caledon, Ontario L7K 1L7

 HYPERLINK "mailto:alex_stovemaster@yahoo.ca" alex_stovemaster@yahoo.ca 

www.stovemaster.com

Introduction

A series of 14 test runs was performed on a masonry heater in 2009 -
2010. The tested masonry heater is of the Double Bell design, with size
and layout comparable to the majority of heaters being built in the
North America today. The heater has a large firebox designed to handle a
wood charge of 50 lbs.

Particulate emissions were sampled using Oregon Method 41 (OM-41 or
Condar Method), which uses a portable emissions sampler that
incorporates dilution.

Different firebox configurations and different ways for supplying
primary and secondary combustion air where tested.

Calibration and Accuracy

This was a low budget study done for in-house research purposes.
Calibration gases were not used. 6” glass filters were used in the
Condar sampler. Filter dessication was not used, since it was determined
by testing that it did not make any appreciable difference. Filters were
weighed immediately after test termination.

To allow comparability between tests and avoid inaccuracy, the following
methods were used:

A model Testo 330-1 commercial combustion analyzer, which is widely used
in Europe.  Self-diagnostics was performed before each run.

A sample weight was weighed before and after each run, to detect drift
in the calibration of the analytical balance.

Test Results 

A summary of test results is presented in Table 3.

Average PM Factor for 12 cordwood tests was 1.01 g/kg.

With exception of two tests, the tests were performed on a slightly warm
heater (48hrs since the last burn).  With this factor and all variations
in firebox and air supply design, all tests fall in the range of
0.45-1.7g/kg.

Two last tests were performed using a wet hardwood crib with individual
pieces reaching moisture content up to 35% to simulate the worst case
scenario. They generated the highest PM values recorded of 3.5g/kg and
3.8g/kg, in slow, smoldering starts.

The average PM factor from all tests including two wet crib tests was
1.35 g/kg.

More detailed results, including raw data and detailed fueling data are
available upon request, and will be made available online at  HYPERLINK
"http://www.stovemaster.com" www.stovemaster.com  soon.

The column headings in Table 2 (next page) are as follows:

PM g/kg: particulate emissions factor as determined by Oregon  Method 
41 (OM-41 or Condar method)

CO emissions factor, using OM-41

Eff: Overall efficiency, using OM-41

Moisture: Wood  moisture, % dry basis

Load : fuel load in lbs. Tests were single loads.

Pieces #: Total number of fuel pieces

Surf/Vol: some tests included a surface/volume factor for the fuel
pieces

Kindling: weight of kindling in lbs (included in total fuel load)

Cold/Warm heater/fuel: CC means cold heater and cold fuel, whereas WW
means warm heater (fired 24 hrs previously) and room termperaturefuel.

Ignition: default is log cabin stacking with kindling from the side. 

Species.

Table 3. DATA SUMMARY --Particulates, Carbon Monoxide and Efficiency
for 14 Double Bell heater tests

Run	PM	CO 	Eff.	Moisture	Load 	Pieces	Surf/Vol	Kindling 	Cold/Warm
Ignition	Species

 	g/kg	g/kg	%	%	lbs	 	 	lbs	heater/fuel	 	 

Average	1.01	53.76	76.03	19.62	49.44	8.58	3.24	2.2	 	 	 

 	 	 	 	 	 	 	 	 	 	 	 

TL-001	1.11	43.25	73.13	20.50	48.40	8	3.02	2.2	s.warm/w	side	maple

TL-002	1.34	61.75	77.07	17.00	48.50	8	2.96	2.2	s.warm/w	side	maple

TL-004	1.67	74.47	73.99	18.00	49.40	9	3.29	2.2	s.warm/w	side	maple

TL-005	0.98	58.46	77.06	20.90	49.20	8	3.42	2.2	s.warm/w	side	maple

TL-006	0.62	47.85	78.53	20.00	51.00	9	3.29	2.2	warm/w	side	maple

TL-007	0.45	48.55	74.64	20.00	48.70	8	3.09	2.2	warm/w	side	maple

TL-008	0.60	57.80	78.87	20.00	49.00	9	3.45	2.2	s.warm/w	side	maple

TL-009	0.61	49.10	76.20	20.00	49.10	8	3.10	2.2	s.warm/w	side	maple

TL-010	1.35	57.97	75.88	20.00	49.60	10	3.37	2.2	s.warm/w	side	maple

TL-011	1.35	61.70	73.00	18.00	50.00	10	3.61	2.2	s.warm/w	side	maple

TL-012	1.36	48.14	78.00	20.50	50.90	8	2.94	2.2	s.warm/w	side	maple

TL-013	0.66	36.13	76.00	20.50	49.50	8	3.30	2.2	s.warm/w	side	maple













	Wet hardwood crib runs (up to 35% moisture pieces):







TLC-01	3.80	38.69	63.57	24.60	36.00	9	4.07	4.50	s.warm/w	bottom	maple

TLC-02	3.05	44.00	63.52	24.10	36.20	9	4.04	4.50	s.warm/w	bottom	maple













	s.warm - "slightly warm" - 48hrs since last burn.







	

Key:

PM factors less than 1 g/kg are highlighted in green

PM factors between 1 – 2 g/kg are in white

PM factors greater than 2 g/kg are highlighted in brown

 

4.)  Discussion

The 52 “normal” HeatKit runs, averaging 0.97 g/kg, had an average
burn rate of 12.2 kg/hr and an average PM emissions rate of 11.81 g/hr.
The 2 hr burn duration on this large (heavy) heater yields a 24 hr
heating time. Thus, the emissions rate is 11.81 g/hr for 8% of the
heating cycle, and 0 g/hr for 92% of the heating cycle, or an averaged
rate of 0.98 g/hr over the heating cycle.

In comparison, the Swedish heater tested by OMNI is lighter, and has a
shorter heating cycle. The fuel load of the Swedish heater averaged 0.64
of the fuel load of the HeatKit. Emissions between the two heaters are
more realistically compared with the emissions factors, than with the
emissions rates. The Condar emissions factor for the Swedish averages
2.57 times that of the HeatKit, but the emissions rate averages 0.72
times. Emissions rate reporting favors smaller heaters, which normally
burn less wood and heat less space.

A 2009 study by Cold Climate Housing Research Center in Fairbanks,
Alaska, measured PM emissions in an EPA wood stove, a masonry heater,
and a multi-fuel pellet stove, and provides the following emissions data
based on assumed daily device use patterns (Reference 4). For the EPA
wood stove, it is assumed that it is “damped down” at night and
fired at high burn rate for the portion of the day when the house is
occupied:

Summary of Emissions for Assumed Daily Device Use Pattern, as Tested	 
 	 

Device	Use Period	Length of Burn      Low Burn rate (hr)	Length of Burn 
    High Burn rate (hr)	Weight of Fuel Burned (kg)	Total Heat Delivered
(Btu)	Average Emissions Rate over Heating Cycle (g/hr)	Emissions per
Heat Output (g/100,00 Btu)

 	 	 	 	 	 	 	 

EPA Wood stove	Weekend	5	10	28.5	247,747	6.3	34.7

EPA Wood stove	Weekday	5	4	14.6	168,395	9.0	48.5

Masonry Heater	Every Day	NA	4	41.3	521,610	3.5	16.4

Multi-fuel Stove/Barley	Every Day	NA	24	21.8	209,957	3.6	40.6

Multi-fuel Stove/Pellets	Every Day	NA	24	93.2	1,054,322	5.6	12.7



In this study, the EPA stove was certified at 2.6 g/hr. It tested at
CCHRC with local softwood cordwood at 2.3 g/hr at high burn rate, and at
14.5 g/hr at low burn rate. In a less severe climate than the Alaska
interior, it might be expected to operate at low burn for a greater
portion of the heating cycle, which would increase emissions. If the
masonry heater in a milder climate were fired once per day instead of
twice, the average emissions over the 24 hr heating cycle would drop to
1.75 g/hr, at half the heat output.

Low output does not increase emissions as it does with the wood stove in
this study. However, the emissions rate would not reflect this unless it
is allowed to be averaged over the heating cycle.

If EPA were required to set a reasonable g/hr limit for masonry heaters,
these considerations should be taken into account.

References

1.)  “Warm Homes Technical Report: Real-life Emissions Testing of
Pellet Burners in Tokoroa”, New Zealand Ministry for the Environment,
2005

 HYPERLINK
"http://www.mfe.govt.nz/publications/energy/emissions-testing-pellet-bur
ners-tokoroa-jun07/html/index.html"
www.mfe.govt.nz/publications/energy/emissions-testing-pellet-burners-tok
oroa-jun07/html/index.html 

2.)    HYPERLINK "http://heatkit.com/research/lopezq.htm"
heatkit.com/research/lopezq.htm 

3.)  “Determination of Condensable Particulate Woodstove Emission
Factors Using Condar’s Emissions Sampler”, Stockton Barnett, 1983

 HYPERLINK "http://heatkit.com/docs/condar.PDF"
heatkit.com/docs/condar.PDF 

4.) “Support for Developing a Sustainable Fire Load Reduction Program
by Creating and Expanding Wood-Energy Enterprises”, Dave Misiuk, P.E.,
Cold Climate Housing Research Center, Fairbanks, Alaska, 2009.

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