Cord Wood Testing in a Non-Catalytic Wood Stove 

Final Report 

Prepared for: 

U.S. Environmental Protection Agency 

EPA Contract No. EP-D-10-096, WA 4-04 

EC/R Incorporated, Prime Contractor 

Prepared by: 

Brookhaven National Laboratory 

T. Butcher, R. Trojanowski, G. Wei

June 30, 2014 
1 

Abstract

EPA Method 28 and the current wood stove regulations have been in-place since 1988. Recently, 

EPA proposed an update to the existing NSPS for wood stove regulations1

 which includes a plan 

to transition from the current crib wood fuel to cord wood fuel for certification testing. Cord wood 

is seen as generally more representative of field conditions while the crib wood is seen as more 

repeatable. In any change of certification test fuel, there are questions about the impact on 

measured results and the correlation between tests with the two different fuels. The purpose of the 

work reported here is to provide data on the performance of a non-catalytic stove with cord wood. 

The stove selected has previously been certified with crib wood which provides a basis for 

comparison with cord wood. Overall, particulate emissions were found to be considerably higher 

with cord wood. 

Introduction

Today, in both developed and developing countries, biomass remains an important energy source 

for heating and cooking. Wood stoves in particular are the most popular wood heating option as 

they are flexible and economical. Wood stoves supply heat directly to the space, unlike central 

boilers/furnaces which require a system of ducts to supply heat. They’re easy to install, require 

little space, and involve little maintenance. 

Currently wood stoves in the U.S. are tested 

for certification using EPA Method 28 

“Certification and Auditing of Wood 

Heaters”2,3. This requires testing in 4 burn 

categories using dimensional lumber (cribs) 

of Douglas Fir. The Douglas Fir crib fuel 

consists of 2 x 4 and/or 4 x 4 pieces which 

are nailed or stapled together with the 

proper spacing to establish consistency of 

the fuel load (see Figure 1). Tests run with 

crib wood do not permit any round or 

special angular cuts to the fuel pieces and 

are geometrically similar to the shape of the 

firebox. The crib fuel must not be treated or 

kiln-dried and also meet the moisture 

 

1

 U.S. EPA, Standards of Performance for New Residential Wood Heaters, New Residential Hydronic Heaters and 

Forced-Air Furnaces, and New Residential Masonry Heaters; Proposed Rule, Federal Register, Vol. 79, No. 22, 

Feb3, 2014. 

2

 “Method 28- Certification and Auditing of Wood Heaters”, EPA, http://www.epa.gov/fem/methcollectns.htm 3

 http://www.epa.gov/ttnemc01/promgate/m-28.pdf 

Figure 1: Test fuel crib arrangement
2 

requirement of 16 to 20% on a wet basis (19 to 25% on a dry basis). Despite the efforts to maximize 

consistency amongst tests and stoves, the argument still remains that cord wood (split logs) is more 

representative of field use and therefore real-world emissions. Under Method 28 particulate 

emissions are measured using either a dilution tunnel method (5G) or an in-stack method (5H). 

In the proposed new regulations for residential wood heating devices, known as the New Source 

Performance Standards or “NSPS”, the EPA has proposed switching the fuel used for testing 

devices in future years- from crib to cord wood. 

The goal of this work was to compare the emission test results for cribs and cord wood in a noncatalytic stove. Crib data was provided by EPA from the EPA certification test data. In this testing 

particulates were measured using method 5H in contrast to method 5G used in the current work. 

Cord wood tests were conducted in accordance to the current draft ASTM method and 

considerations from Method 28. 

Experimental

The stove tested for this report was an EPA certified non-catalytic stove, towards the cleaner end 

of the EPA certification list, i.e. <2.0 g/hr with crib wood. To ensure complete combustion the 

stove includes an insulated firebox, a system of baffles to create a longer, hotter gas flow path, and 

a damper to control the amount of air introduced under the fire and to the glass door “air wash”. 

Secondary air is introduced through ports at the top of the combustion chamber. 

The fuel test charge was cord wood, specifically red oak with an average moisture content of 19 

to 25% on a dry basis. During testing, fuel pieces were placed in the firebox parallel to the 

longest firebox dimension. A full load was considered as 7 pounds per cubic foot in all tests, 

which is equivalent to 24 pounds of the fuel charge for the appliance. This loading was 

selected for consistency with the prior Method 28 crib wood data. This loading is 

different than is being considered in the developing ASTM method. 

The test fuel was prepared by the State University of New York, College of Environmental 

Science and Forestry (ESF) under the direction of Dr. William Smith. The preparation 

involved conditioning fresh cord wood under controlled temperature and humidity conditions 

for time periods on the order of weeks. The moisture measurement method developed in the 

work at ESF was used in this work and involves averaging multiple “shell” and “core” 

measurements4

. An example of the wood moisture data from May 20th, may be seen in Table 1 

 

4

 Smith, W.B., Evaluation of Wood Fuel Moisture Measurement Accuracy for Cord wood-Fired Advanced Hydronic 

Heaters”, Report 14-12 to NYSERDA, March 2014. Available at www.nyserda.ny.gov. 
3 

Table 1: Cord wood Moisture Content Determination May 20th, 2014 

Test # Cat 4     Name/s: GW          

Date: 5/20/2014     Moisture Meter: RDM3        

Weight

A ‐ 

end    

B ‐ 

center    

C –

end   

Predicted

Piece %MC    

Piece

# lbs shell Core shell Core shell Core A‐B B‐C

A‐B &

B‐C

1 5.16 10.9 17.1 13.3 24.9 12.3 17.3 16.0 17.0 16.5

2 4.89 13.1 22.1 18.8 31.9 13.6 23.1 20.4 21.9 21.1

3 4.13 12.3 21.2 17.8 32.1 12.3 17.3 18.8 19.9 19.4

4 5.18 12.1 24.5 20.4 33.4 14.4 21.3 21.0 22.4 21.7

5 4.75 17.3 38.4 15.8 41.5 16.7 37.4 27.9 27.9 27.9

Sum 24.1           Average 20.8 21.8 21.3

The fuel that was used for the tests was free of any notable decay, fungus and loose bark. The

fuel charge and kindling was loaded as per the manufacturer’s specifications. Kindling was 

weighed prior to each test; however, moisture of the kindling pieces was not recorded. The 

dimensions of each fuel piece were recorded for each test as well. An example from May 20th may 

be seen in Figure 2. 

Figure 2: Fuel wood dimensions May 20th, 2014 
4 

The stove vented into a dilution tunnel hood that collected exhaust gas and mixed it with room 

air. The dilution ratio was controlled by a set of in-line dampers that allowed the air velocity 

in the dilution tunnel to be adjusted. The dilution tunnels seams and joints were sealed to 

prevent leakage. The velocity and pressure were measured with a pitot tube and digital 

pressure gauge through each test. The dilution tunnel had a diameter of 8 inches and met the 

specifications of ASTM E2515-10. 

Particulate emission measurements were made from the dilution tunnel and conducted in

compliance with ASTM E2515 Standard Test Method for Determination of Particulate Matter 

Emissions Collected in a Dilution Tunnel. Two identical dual-filter EPA Method 5 sampling 

trains5 were operated simultaneously. The two sampling trains allow for quality control and 

confirmation of the PM data collected over a period. Each sampling train consisted of two glass 

fiber filters in series that were each 47 millimeters in diameter. 

Filters and probes were desiccated for at least 24 hours or until the weight remained constant. 

The components were weighed prior to the test. The probes were also rinsed with acetone before

sampling and initial weights are taken to remove any PM that may have accumulated in the

probe from prior tests. When loading and measuring any filters and probes, gloves and tweezers 

were used to eliminate excess weights attributed to dirt and oils from skin contact. Leak checks 

of the sampling system were performed before start of testing to ensure no leakage exists that 

would result in less dilution tunnel gas passing through the filters than indicated by the

metering system. 

Flue gas samples for analysis were taken from the dilution tunnel and directly from the flue. For 

sampling from the dilution tunnel, water vapor was removed using a thermoelectric cooler/drier. 

Gas analysis in the dilution tunnel included oxygen and carbon monoxide. Analysis of samples 

from the flue gas included oxygen. A decision was made to measure carbon monoxide from the

dilution tunnel to allow direct calculation of the emission rate of CO (concentration × dilution 

tunnel flow rate). 

Carbon monoxide was measured using a Rosemount Analytical model 880 NDIR Carbon 

Monoxide analyzer. Oxygen was measured in both the dilution tunnel and the hot stack via a

Beckman model 755 Oxygen Analyzer. Both analyzers have a set of four ranges: 10%, 25%, 

50% and 100%. The signals from all analyzers were logged at a 5 second intervals. 

Temperatures were also measured continuously at five second increments, using TC-08 

thermocouple data loggers made by Pico Technologies with type K thermocouples. Type K 

 

5 Model 511 from Apex Instruments 
5 

thermocouples are capable of measuring temperatures to within +/- 1.5°. The thermocouples 

were calibrated using an Omega CL1000 dry calibration block and were in compliance with 

National Institute of Standards and Technology (NIST) Monograph 175, Standard Limits of 

Error. 

Test Plan

Three emission tests in each of the four categories of Method 28 were planned to allow evaluation 

of reproducibility with cord wood and provide consistent data for comparison with crib wood. 

However, with cord wood, the size, species, and moisture content of the test fuel can all have 

impacts on the test results. Therefore, for the purposes of this work, the test cord wood was guided 

by draft cord wood specifications and procedures under active development by ASTM. 
6 

Test Results		

Testing was successfully completed in Method 28 Categories IV, III, and II. It was not found 

possible to achieve the Cat. I burn rate with this fuel even when the air control damper was fully 

closed. In this case Method 28 provides a method for determining average emissions based on 

weighting the results of the other three categories in which the stove was tested. It should be noted 

that in the earlier certification testing with crib wood, Category I operation was also not achieved. 

Table 2, below provides a summary of the tests done in each category and includes run-average 

burn rate. For each of the three categories achieved in testing Figures 3 to 14, below provide a 

comparison of the measured trends of the key parameters along with the same parameters measured 

during crib wood testing. The crib wood data was adopted from the submitted certification test 

reports. 

Table 2: Outline of Tests Completed 

Category Fuel Date Burn Rate (kg/hr) 

IV Crib -

1 2.35 

IV Cord 19-May 2.46 

IV Cord 20-May 2.33 

IV Cord 21-May 2.57 

III Crib -

1 1.77 

III Cord 23-May 1.58 

III Cord 28-May 1.51 

III Cord 29-May 1.82 

III Cord 30-May 1.32 

III Cord 4-June 1.31 

II Crib -

1 1.12 

II Cord 5-June 1.03 

II Cord 9-June 1.13 

II Cord 10-June 1.09 

II Cord 11-June 1.16 

I Crib -

1,2 0.99 

1. Results reported in 2004 as part of qualification test report done by test lab. 

2. As of July 1, 1990, Method 28 allowed Cat 1 to be less than 1.00 versus the original 

<0.80. [Section 5.2 of Method 28] 
7 

Cat IV

The Cat IV trend comparisons are shown in Figures 3 to 6 below. In this case the burn rate, flue 

gas oxygen, and flue gas temperature trends are seen as very similar between the cord- and crib 

wood cases. In addition there is very good repeatability among the cord wood tests, i.e. within 3% 

of the average g/hr. It is important to mention the amount of fuel consumed within the first 30 

minutes was 7.5, 7.5, 9.0 lbs for the cord wood, and 9.6 lbs for the crib wood (cord wood tests 

May 19th, May 20th, and May 21st, respectively). On the 19th, the door was closed immediately 

causing for a slower light off and lesser consumption rate within the first 30 minutes, however it 

was a good match to the crib wood light off from 2004. After some discussion it was decided to 

leave the door open longer (also recommended by the manufacturer) to prevent oxygen starvation 

which can cause higher emissions. 

Table 3: Cat. IV Data Summary 

Cat. IV

RUN # Crib 1 2 3 AVERAGE

Date 2004 19‐May 20‐May 21‐May   

Particulate

Emissions Units                

Concentration mg/m^3  ‐  6.933 6.747 7.037 6.905

Emissions Rate grams/hr 0.78 4.291 4.159 4.355 4.268

Emissions Factor grams/kg 0.33 1.399 1.422 1.269 1.363

Total Mass

Captured Mg 63.6 8.300 8.050 7.200 7.850

                    

Heat Output

(EPA Default) BTU/hr                

                    

Fuel Burn Rates                  

Average Burn

Rate

kg/hr (dry) 2.35 2.46 2.33 2.57 2.45

lb/hr (dry) 5.18 5.43 5.13 5.67 5.41

                    

Fuel Moisture

Content                  

Kindling (wet

basis) % 14.966 N/A N/A N/A N/A

Pretest Fuel (wet

basis) % 18.897 20.1 19.9 21.2 20.4

Test Fuel (wet

basis) % 17.519 20.6 21.3 25.7 22.53
8 

                    

Air to Fuel Ratio    N/A N/A N/A N/A N/A

                    

Average Stack

Gas                  

Avg CO2 % 7.48 N/A N/A N/A N/A

Avg O2 % N/A 12.8 12.9 11.43 12.38

Avg CO % 0.58 0.03 0.03 0.03 0.03

Avg moisture % 6.35 10 10 10 10

                    

Average Stack

Gas Emissions                  

CO g/kg 74.13            

   g/hr 174.14            

                    

Average

Temperatures                  

Stack Gas °F 403 437 420 415 424

Firebox °F 984 N/A N/A N/A N/A

Secondary °F 1093 N/A N/A N/A N/A

Catalytic

Combustor °F N/A N/A N/A N/A N/A

Top °F 311 436 420 459 438

Left Side °F 404 548 555 604 569

Back °F 232 86 86 86 86

Right Side °F 424 378 363 410 384

Bottom °F 352 N/A N/A N/A N/A

Temperature

Change °F  ‐74 ‐86.7 ‐18.4 ‐12.9 ‐39.3

                    

Test Chamber

Environment                  

Average

Barometer in. Hg 30.17 29.97 29.91 29.88 29.92

Average

Temperature °F 79 73 75 67 72

Ambient

Moisture % H2O 1.45            

Relative

Humidity %RH 33.5 33.8 24.4 42 33.4

Air Velocity m/sec 0            

                    

Fuel Weight and

Burn Time                  
9 

Density (dry

basis) gm/cm^3 N/A N/A N/A N/A N/A

Coal Bed Weight Lbs 4.9 6.3 5.6 5.1 5.7

Pre Test Fuel

(inc. kindling) Lbs 47.1 28.8 22.5 28.3 26.5

Test Fuel Lbs 22.5 24.4 23.9 24.2 24.2

Burn Time Min 215 213.92 219.92 190.42 208.1

Figure 3: Cat. IV fuel consumption trends

440

445

450

455

460

465

470

475

0 50 100 150 200 250

Scale Mass (lbs)

Time (min)

Crib

Cord 5/19

Cord 5/20

Cord 5/21
10 

Figure 4: Cat. IV stack temperature trends

Figure 5: Cat. IV stack oxygen trends

0

100

200

300

400

500

600

700

0 50 100 150 200 250

Stack Temperature (F)

Time (min)

Crib

Cord 5/19

Cord 5/20

Cord 5/21

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250

Stack O2 (%)

Time (min)

Crib

Cord 5/19

Cord 5/20

Cord 5/21
11 

Figure 6: Cat. IV carbon monoxide trends

0

100

200

300

400

500

600

0 50 100 150 200 250

CO in Dilution Tunnel (ppm)

Time (min)

Cord 5/20

Cord 5/19

Cord 5/21
12 

Cat III

The Cat III trend comparisons are shown in Figures 7 to 10 below. Again, in this case the burn 

rate, flue gas oxygen, and flue gas temperature trends are seen as very similar between the cordand crib wood cases. However, the cord wood was wetter (22.0%) versus the 2004 crib wood case 

(17.8%). The repeatability in the flue gas oxygen and temperature between the individual cord 

wood tests is not as clear as with the Cat IV tests. The fuel consumed within the first 30 minutes 

for the crib, May 23rd, May 28th, May 29th, May 30th, and June 4th tests was 5.6, 5.7, 7.9, 7.6, 7.6, 

and 6.3 lbs, respectively. For these tests the door was left partially open for a full five minutes after 

the fuel charge was added. 

Table 4: Cat. III Data Summary 

Cat. III

RUN # Crib 1 2 3 4 5 AVERAGE

Date 2004 23‐May 28‐May 29‐May 30‐May 4‐Jun   

Particulate

Emissions Units                      

Concentration mg/m^3  ‐  9.973 13.403 26.009 14.166 25.562 17.822

Emissions Rate grams/hr 1.1 6.461 8.748 17.402 9.398 16.605 11.723

Emissions

Factor grams/kg 0.62 3.185 4.555 7.301 5.495 9.860 6.079

Total Mass

Captured mg 127.8 17.450 24.600 40.000 30.500 53.600 33.230

                          

Heat Output

(EPA Default) BTU/hr                      

                          

Fuel Burn

Rates                        

Average Burn

Rate

kg/hr

(dry) 1.77 1.58 1.51 1.82 1.32 1.31 1.51

lb/hr

(dry) 3.9 3.49 3.33 4.01 2.92 2.89 3.33

                          

Fuel Moisture

Content                        

Kindling (wet

basis) % 13.917 N/A N/A N/A N/A N/A   

Pretest Fuel

(wet basis) % 18.8 19 18.38 17.51 18.7 14.6 17.638

Test Fuel (wet

basis) % 17.8 22.1 21.5 21.58 22.58 22.2 21.992

                          
13 

Air to Fuel

Ratio    N/A N/A N/A N/A N/A N/A N/A

                          

Average Stack

Gas                        

Avg CO2 % 6.76 N/A N/A N/A N/A N/A N/A

Avg O2 % N/A 13.2 12 12.34 12.59 10.8 12.186

Avg CO % 0.87 0.04 0.03 0.04 0.04 0.03 0.0369568

Avg moisture % 5.92 10 10 10 10 10 10

                          

Average Stack

Gas Emissions                        

CO g/kg 117.02                  

   g/hr 207.59                  

                          

Average

Temperatures                        

Stack Gas °F 335 309 281 298 240 248 275.2

Firebox °F 725 N/A N/A N/A N/A N/A   

Secondary °F 953 N/A N/A N/A N/A N/A   

Catalytic

Combustor °F N/A N/A N/A N/A N/A N/A   

Top °F 334 346 336 333 275 295 317

Left Side °F 370 450 444 449 417 417 435.4

Back °F 313 88 82 81 86 84 84.2

Right Side °F 376 330 355 352 318 331 337.2

Bottom °F 325 N/A N/A N/A N/A N/A   

Temperature

Change °F  ‐67.7 ‐99 ‐156.9 ‐69.59 ‐134.28 ‐110.67 ‐114.088

                          

Test Chamber

Environment                        

Average

Barometer in. Hg 30.21 29.8 29.92 30.13 29.96 29.7 29.902

Average

Temperature °F 79 72 71 66 72 76 71.4

Ambient

Moisture % H2O 1.2                  

Relative

Humidity %RH 33.5 99.2 91.2 59.3 58.5 74.6 76.56

Air Velocity m/sec 0                  

                          

Fuel Weight

and Burn Time                        
14 

Density (dry

basis) gm/cm^3 N/A N/A N/A N/A N/A N/A N/A

Coal Bed

Weight lbs 5.3 5 5.3 6 5.7 6.1 5.62

Pre Test Fuel

(inc. kindling) lbs 62.6 26.4 26 26.9 28.6 28.1 27.20

Test Fuel lbs 23 24.5 24 24.2 25 24.7 24.48

Burn Time min 290 328.00 339.17 283.75 398.15 399.02 349.62

Figure 7: Cat. III fuel consumption trends

440

445

450

455

460

465

470

475

0 50 100 150 200 250 300 350 400 450

Scale Mass (lbs)

Time (min)

Crib 2004

Cord 5/23

Cord 5/28

Cord 5/29

Cord 5/30

Cord 6/4
15 

Figure 8: Cat. III stack temperature trends

Figure 9: Cat. III stack oxygen trends

0

100

200

300

400

500

600

700

800

0 50 100 150 200 250 300 350 400

Stack Temperature (F)

Time (min)

Crib

Cord 5/23

Cord 5/28

Cord 5/29

Cord 5/30

Cord 6/4

4

6

8

10

12

14

16

18

20

22

0 50 100 150 200 250 300 350 400

Stack O2 (%)

Time (min)

Crib 2004

Cord 5/23

Cord 5/28

Cord 5/29

Cord 5/30

Cord 6/4
16 

Figure 10: Cat. III carbon monoxide trends

0

200

400

600

800

1000

1200

1400

1600

0 50 100 150 200 250 300 350 400

CO in Dilution Tunnel (ppm)

Time (min)

Cord 5/23

Cord 5/28

Cord 5/29

Cord 5/30

Cord 6/4
17 

Cat II

The Cat. II trend comparisons are shown in Figures 11 to 14 below. In this case the burn rate, flue 

gas oxygen, and flue gas temperature trends are seen as very similar between the cord- and crib 

wood cases. In addition there is very good repeatability among the cord wood tests, i.e., within 

10% of the average g/hr. The cord wood moisture content (19.6 %) was somewhat higher than the 

crib wood case (17.1 %). The consumption of fuel for the first 30 minutes for the crib, June 5th, 

June 9th, June 10th, and June 11th tests was 3.7, 4.5, 3.9, 4.0, and 3.2, respectively. For the Cat. II 

tests, the door was closed completely within two minutes of loading the fuel charge to prevent a 

high initial consumption rate causing for an overall higher consumption rate and higher category. 

Table 5: Cat. II Data Summary 

Cat. II

RUN # Crib 1 2 3 4 AVERAGE

Date 2004 5‐Jun 9‐Jun 10‐Jun 11‐Jun   

Particulate

Emissions Units                  

Concentration mg/m^3  ‐  54.497 72.424 115.583 128.783 92.822

Emissions Rate grams/hr 2.230 36.012 48.088 34.756 41.123 39.995

Emissions

Factor grams/kg 2.000 27.884 34.697 31.174 27.677 30.358

Total Mass

Captured mg 638.600 142.200 181.600 296.650 312.750 233.300

           

Heat Output

(EPA Default) BTU/hr                   

           

Fuel Burn

Rates                     

Average Burn

Rate

kg/hr

(dry) 1.12 1.03 1.13 1.09 1.16 1.10

lb/hr

(dry) 2.47 2.28 2.48 2.39 2.57 2.43

           

Fuel Moisture

Content                     

Kindling (wet

basis) % 13.119 N/A N/A N/A N/A N/A

Pretest Fuel

(wet basis) % 19.041 18.1 15.9 14.9 14.7 15.9

Test Fuel (wet

basis) % 17.118 20 18.9 18.1 21.2 19.55

           

Air to Fuel

Ratio       N/A N/A N/A N/A N/A

           

Average Stack

Gas                     

Avg CO2 % 5.87 N/A N/A N/A N/A N/A
18 

Avg O2 % N/A 13.1 13.4 11.5 11.6 12.4

Avg CO % 1.11 0.03 0.04 0.09 0.08 0.060396

Avg moisture % 5.04 10 10 10 10 10

           

Average Stack

Gas Emissions                     

CO g/kg 160.7   

   g/hr 179.99   

           

Average

Temperatures                     

Stack Gas °F 238 173 174 164 175 171.5

Firebox °F 607 N/A N/A N/A N/A N/A

Secondary °F 692 N/A N/A N/A N/A N/A

Catalytic

Combustor °F N/A N/A N/A N/A N/A N/A

Top °F 268 216 205 219 207 211.75

Left Side °F 306 357 330 333 347 341.75

Back °F 251 88 88 92 92 90

Right Side °F 316 271 295 279 288 283.25

Bottom °F 179 N/A N/A N/A N/A N/A

Temperature

Change °F  ‐77 ‐167 ‐204.5 ‐219.2 ‐142.5 ‐183.3

           

Test Chamber

Environment                     

Average

Barometer in. Hg 30.08 29.55 29.87 29.86 30.01 29.8225

Average

Temperature °F 75 69 69 73 73 71

Ambient

Moisture % H2O 1.2               

Relative

Humidity %RH 29.5 93.8 91.7 88.35 71.95 86.45

Air Velocity m/sec 0   

           

Fuel Weight

and Burn Time                     

Density (dry

basis) gm/cm^3 N/A N/A N/A N/A N/A N/A

Coal Bed

Weight lbs 5.6 5.9 6.7 5.6 5.3 5.875

Pre Test Fuel

(inc. kindling) lbs 64.2 27.1 28.2 28.4 27.9 27.9

Test Fuel lbs 22.6 23.9 24 24.9 25.8 24.65

Burn Time min 455.00 503.17 470.75 510.92 475.00 489.9583
19 

Figure 11: Cat. II fuel consumption trends

Figure 12: Cat. II stack oxygen trends

440

445

450

455

460

465

470

475

0 100 200 300 400 500 600

Scale Mass (lbs)

Time (min)

Crib 2004

Cord 6/5

Cord 6/9

Cord 6/10

Cord 6/11

4

6

8

10

12

14

16

18

20

22

0 100 200 300 400 500 600

Stack O2 (%)

Time (min)

Crib 2004

Cord 6/5

Cord 6/9

Cord 6/10

Cord 6/11
20 

Figure 13: Cat. II stack temperature trends

Figure 14: Cat. II carbon monoxide trends

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Stack Temperature (F)

Time (min)

Crib

Cord 6/5

Cord 6/9

Cord 6/10

Cord 6/11

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600

CO in Dilution Tunnel (ppm)

Time (min)

Cord 6/5

Cord 6/9

Cord 6/10

Cord 6/11
21 

Wet Cord wood Evaluation

In an exploratory test a high burn rate test was done using very wet cord wood. This was done 

specifically to provide an evaluation of the impact that burning very we wood might have on 

emissions. Test procedures were the same as was followed with the other test fuels. Wood 

moisture content was 48.4% on a wet basis. Particulate emissions were found to be extremely high, 

50.6 g/hr over the run, 11.8 times higher than the average emission rate with the drier test fuel in 

Category IV. 

Discussion

The test results presented here clearly show much higher emissions with the cord wood tested vs 

the crib wood results included in the certification test report. This is particularly clear for the low 

input, Cat II test. The burn rate, flue gas temperature, and flue gas oxygen however, would not 

lead to the obvious conclusion that the burn characteristics with the cord wood are very much 

different than with the crib wood. The only notable exception to this is the Cat II test, where the 

stack temperature was clearly higher for the crib wood tests. 

There are several factors which could contribute to the differences observed between the cord and 

crib wood results: 

 The cord wood does not have the defined air flow path between the pieces as there is in the 

crib wood tests. It should be noted that in loading the cord wood into the firebox great 

effort was taken to space the pieces as per the manufacturer’s loading instructions and with 

spacing between the pieces as uniform as possible. 

 The crib wood tests were done with Douglas Fir while the cord wood used here was red 

oak. It should be noted that red oak is an acceptable fuel in at least the draft version of the 

ASTM cord wood protocol being evaluated in this work. 

 With the specific cord wood used in this test, the shell was drier than the average and the 

core wetter. This could have affected the burn characteristics. 

During the Cat II, low burn rate tests, the glass door on the front of the stove became blackened 

and considerable carbon deposits were noted in the top of the stove and flue pipe after the test. 

This observation suggests that there was not adequate air in the primary section during this test. 

The overall exhaust flue gas oxygen was high, indicating adequate air for combustion, but much 

of this air may have been entered as secondary air and not contributed to achieving burnout of the 

semivolatile organics. For optimal performance of this stove on cord wood, some rebalancing of 

the primary air / secondary air ratio may be required. It is possible as well that the details of the 

air damper setting and the procedure for loading and the timing of the startup operations 

contributed to differences between cord wood and reported crib data. 

The results in this work can be compared with those of a catalytic stove conducted independently 

of this work and by a manufacturer. In the case of the catalytic stove, a direct comparison was 

made between cord and crib wood test results. The emission rate of particulates was found to be 

2.2 times higher with cord wood in Category II. At higher burn rates the emissions were closer 

with the cord wood emission rate 32% higher. This comparison is made based on direct method 

5G emission measurements. 
22 

Conclusions

These results indicate that there can be very significant differences between the emissions during 

certification testing between cord wood and the Method 28 crib wood. In the lowest burn rate 

tested, the particulate emission rate with cord wood was found to be 18 times higher than was 

reported with the crib wood testing.