S1 

Semi-volatile and Volatile Organic Compound Emissions from 

Outdoor Wood-Fired Hydronic Heaters 

Johanna Aurell1, Brian K. Gullett2,*, Dennis Tabor2, Abderrahmane Touati3, Lukas Oudejans4

1National Research Council Post Doctoral Fellow to the U.S. Environmental Protection Agency 

2U.S. Environmental Protection Agency, Office of Research and Development, National Risk 

Management Research Laboratory, Research Triangle Park, NC 27711, USA 

3ARCADIS G&M, Inc., 4915 Prospectus Drive, Durham, NC 27713, USA 

4U.S. Environmental Protection Agency, Office of Research and Development, National 

Homeland and Security Research Center, Research Triangle Park, NC 27711, USA 

*Corresponding Author: gullett.brian@epa.gov, 919/541-1534 

Summary 

Pages: 7 

Figures: 3 

Tables: 5 

 
S2 

Figure S1. Illustrations of four different outdoor wood-fired hydronic heater technologies 

investigated. 

Figure S2. Experimental set-up, not to scale. 

Primary 

air supply

Secondary 

air supply

Bottom fed pellet burner

Post-combustion 

zone

Combustion 

zone

Primary 

air supply

Secondary 

air supply

Bottom fed pellet burner

Post-combustion 

zone

Combustion 

zone

Up-draft 

combustion

Down-draft 

combustion

Combustion and 

gasification

Bottom fed pellet 

burner

Primary 

air supply

Secondary 

air supply Combustion zone

Secondary air supply

Primary air supply

Combustion zone

Secondary 

super-heated 

air supply

Primary 

air supply

Secondary combustion zone

Combustion zone

PCDD/PCDF

CO and CO2

Naphthalene/Benzene 

REMPI-TOFMS

VOC

Summa Canister

CO

Outdoor Indoor 

Induction Fan

Heat exchanger

Hot water

Cooling water

Hot water recirculation loop Wall

Heater

PAH

Hood cone

Stack

Dilution duct
S3 

Figure S3. Twenty four hour heat load profile for a 232 m2

 home in Syracuse, New York, USA. 

 
S4 

Table S1. Fuel properties. 

Properties Fuel 

Red oak White pine White ash Hardwood pellets 

Ash (%) 1.5 0.44 0.75 0.52 

Moisture (%) 22 9.6 9.0 7.2 

Volatile Matter (%) 84 88 NA 84 

Fixed Carbon (%) 14 11 NA 14 

Carbon (%) 49 52 51 50 

Chlorine (ppm) 38 36 NA 44 

Hydrogen (%) 6.0 6.6 NA 5.9 

Nitrogen (%) <0.5 <0.5 NA <0.5 

Sulfur (%) <0.05 <0.05 <0.05 <0.05 

Heating Value (MJ/kg) 19.5 21.6 15.0 19.8 

* NA – Not analyzed. 

Table S2. PCDD/PCDF Emission Factors (ND = DL; ND = 0 within parentheses). 

Unit Fuel 

Number 

of 

Samples 

PCDD/PCDF WHO-TEQ Total PCDD/PCDF 

ng TEQ/kginput ng TEQ/MJinput ng/kginput ng/MJinput

Conventional HH Red oak 3 1.1 (1.0) 0.054 (0.053) 26 1.3 

STDV 0.76 (0.78) 0.039 (0.040) 27 1.4 

Conventional HH Red oak + refuse 2 1.9 (1.8) 0.098 (0.093) 75 3.8 

RDV 0.45 (0.59) 0.023 (0.030) 4.5 0.23 

Conventional HH White Pine 3 0.63 (0.24) 0.029 (0.011) 11 0.53 

STDV 0.21 (0.077) 0.0097 (0.0036) 1.6 0.075 

Conventional HH White Ash 2 0.37 (0.37) 0.025 (0.024) 13 0.89 

RDV 0.064 (0.078) 0.0061 (0.0052) 2.0 0.38 

Three stage HH Red oak 3 0.11 (0.079) 0.0056 (0.0041) 4.2 0.22 

STDV 0.022 (0.036) 0.0011 (0.0018) 1.5 0.075 

U.S. Downdraft Red oak 3 0.080 (0.023) 0.0041 (0.0012) 2.0 0.10 

STDV 0.0077 (0.0087) 0.00039 (0.00044) 0.60 0.031 

European pellet# Red oak 1 0.28 (0.25) 0.014 (0.012) 26 1.3 

STDV = standard deviation, RDV = Relative deviation (only two tests), # = STDV Not 

applicable (only one test). 

 
S5 

Table S3. PCDD/PCDF emission factors for the different heater/fuel combinations, in ng 

TEQ/MJinput. 

Conventional HH Three stage HH U.S. Downdraft European 

pellet 

Red Oak Red Oak + 

Refuse White Pine White Ash Red Oak Red Oak Red Oak 

2,3,7,8-TCDD 0.0047 

[0.0035] 

0.0088 

[0.0054] 

0.0044 

[0] 

0.00094 

[0] 

0.0006 

[0] 

0.00066 

[0] 

0.0035 

1,2,3,7,8-PeCDD 0.020 0.029 0.010 

[0] 

0.011 0.0018 

[0.0011] 

0.0012 

[0] 

0.0011 

[0] 

1,2,3,4,7,8-HxCDD 0.0010 0.0012 0.0010 

[0] 

0.00037 0.00014 

[0.000076] 

0.00015 

[0] 

0.00010 

[0] 

1,2,3,6,7,8-HxCDD 0.0018 0.0033 0.0011 

[0.00031] 

0.00094 0.00022 

[0.00028] 

0.00015 

[0] 

0.00010 

[0] 

1,2,3,7,8,9-HxCDD 0.0012 0.0027 0.00092 

[0.00045] 

0.00078 0.00021 0.00015 0.00010 

[0] 

1,2,3,4,6,7,8-HpCDD 0.00083 0.0024 0.00040 0.00056 0.00011 0.000057 0.000071 

OCDD 0.000085 0.00024 0.000049 0.000055 0.000011 0.0000056 0.0000053 

Sum PCDD 0.029 

[0.028] 

0.048 

[0.045] 

0.018 

[0.0012] 

0.013 

[0.013] 

0.0030 

[0.0018] 

0.0024 

[0.00021] 

0.0050 

[0.0036] 

 

2,3,7,8-TCDF 0.0038 0.013 0.00094 

[0] 

0.0015 0.00042 0.00010 

[0] 

0.0062 

1,2,3,7,8-PeCDF 0.0013 0.0024 0.00043 

[0.00034] 

0.00033 0.00010 

[0.000085] 

0.000050 

[0.000033] 

0.00026 

2,3,4,7,8-PeCDF 0.0088 0.021 0.0049 0.0037 0.0010 0.00062 

[0.00046] 

0.0018 

1,2,3,4,7,8-HxCDF 0.0037 0.0048 0.0017 0.0012 0.00035 0.00031 0.00035

1,2,3,6,7,8-HxCDF 0.0038 0.0040 0.0015 0.00089 0.00028 

[0.00015] 

0.00017 

[0.00011] 

0.00027 

1,2,3,7,8,9-HxCDF 0.00028 

[0.00018] 

0.00064 

[0] 

0.00063 

[0.00033] 

0.00017 

[0] 

0.00010 

[0.000028] 

0.00018 

[0] 

0.000094 

[0] 

2,3,4,6,7,8-HxCDF 0.0018 0.0022 0.00093 0.00060 0.00024 

[0.00022] 

0.00016 

[0] 

0.000083 

[0] 

1,2,3,4,6,7,8-HpCDF 0.00066 0.00069 0.00044 0.00024 0.000089 0.000042 0.000039 

1,2,3,4,7,8,9-HpCDF 0.00012 0.00015 0.000056 

[0.000031] 

0.000051 0.000041 0.000034 

[0] 

0.0000079 

[0] 

OCDF 0.000013 0.000017 0.000016 0.0000058 0.0000041 0.0000048 

[0] 

0.0000018 

Sum PCDF 0.024 

[0.024] 

0.049 

[0.049] 

0.011 

[0.10] 

0.085 

[0.085] 

0.0026 

[0.0023] 

0.0017 

[0.0010] 

0.0091 

[0.0089] 

Sum PCDD/PCDF 0.054 

[0.053] 

0.10 

[0.093] 

0.029 

[0.011] 

0.022 

[0.022] 

0.0056 

[0.0041] 

0.0041 

[0.0012] 

0.014 

[0.012] 

*

 Average value for congeners with not detectable congener equal to 0 within brackets. 2005 WHO-TEF. 

 
S6 

Table S4. PAH Emission Factors in mg/MJinput. 

Conventional HH Three stage HH U.S. Downdraft European 

Red Oak 

Red Oak + 

Refuse 

White 

Pine 

White 

Ash 

Red Oak Red Oak Pellets 

Naphthalene 12 6.6 22 18 2.4 6.9 0.23 

Acenaphthylene 3.7 2.3 15 4.6 0.67 1.40 0.058 

Acenaphthene 0.27 0.23 1.3 0.32 0.07 0.092 0.0035 

Fluorene 0.96 0.70 3.2 1.2 0.18 0.28 0.013 

Phenanthrene 2.0 1.5 6.1 3.0 0.58 0.86 0.074 

Anthracene 0.46 0.33 1.3 0.75 0.10 0.17 0.012 

Fluoranthene 0.60 0.34 1.3 1.2 0.13 0.28 0.041 

Pyrene 0.62 0.32 1.2 1.1 0.10 0.26 0.043 

Benzo(a)anthracene 0.18 0.093 0.45 0.36 0.027 0.072 0.0049 

Chrysene 0.17 0.093 0.42 0.33 0.029 0.077 0.0047 

Benzo(b)fluoranthene 0.09 0.055 0.24 0.22# 0.019 0.037 0.0035 

Benzo(k)fluoranthene 0.13 0.047 0.28 0.26# 0.007 0.043 0.0014 

Benzo(a)pyrene 0.16 0.076 0.36 0.33# 0.021 0.049 0.0031 

Indeno(1,2,3-cd)pyrene 0.065 0.041 0.15 0.15# 0.011 0.023 0.0027 

Dibenz(a,h)anthracene 0.0070 0.29 0.040#

0.035# 0.19#

 0.85# 0.00021 

Benzo(ghi)perylene 0.093 0.046 0.15 0.19# 0.0090 0.025 0.0025 

Total PAH 21 13 54 32 4.6 11 0.49 

# Method reporting limit. 

 
S7 

Table S5. PAH Emission Factors in mg/kginput. 

Conventional HH Three stage HH U.S. Downdraft European 

Red Oak 

Red Oak + 

Refuse 

White 

Pine 

White 

Ash 

Red Oak Red Oak Pellets 

Naphthalene 229 128 485 274 47 135 4.5 

Acenaphthylene 73 44 323 69 13 27 1.1 

Acenaphthene 5.3 4.4 29 4.8 1.4 1.8 0.069 

Fluorene 19 14 70 18 3.6 5.4 0.26 

Phenanthrene 38 30 132 45 11 17 1.5 

Anthracene 9.0 6.5 29 11 1.9 3.3 0.24 

Fluoranthene 12 6.7 28 18 2.5 5.4 0.82 

Pyrene 12 6.3 26 17 2.0 5.1 0.86 

Benzo(a)anthracene 3.5 1.8 9.7 5.4 0.52 1.4 0.10 

Chrysene 3.4 1.8 9.0 5.0 0.56 1.5 0.094 

Benzo(b)fluoranthene 1.8 1.1 5.1 3.0#

 0.37 0.72 0.069 

Benzo(k)fluoranthene 2.5 0.92 6.1 3.7#

 0.14 0.84 0.029 

Benzo(a)pyrene 3.1 1.5 7.7 4.6#

 0.41 0.96 0.061 

Indeno(1,2,3-cd)pyrene 1.3 0.80 3.3 1.9#

 0.22 0.45 0.053 

Dibenz(a,h)anthracene 0.13 5.5 0.86#

 0.37# 3.6# 17# 0.0041 

Benzo(ghi)perylene 1.8 0.90 3.3 2.6#

 0.18 0.48 0.049 

Total PAH 415 254 1166 483 89 223 9.8 

# Method reporting limit.