The Interim Wood Stove Catalytic Combustor Longevity Study

Prepared for:

The Catalytic Hearth Coalition (CHC)

Prepared by:

Lyrik Pitzman, Thomas Christensen, Jeremy Clark and James Houck

OMNI Environmental Services, Inc.

13327 NE Airport Way

Portland, OR 97230

OMNI Project #: 122-E-08-0

January 4, 2010
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Executive Summary

Introduction

Catalyst-equipped wood-fire heaters represent a significant portion of the heaters present in houses 

with wood stoves. Historically, some industry participants have believed catalyst-equipped woodfire stoves and their associated catalytic combustors experience accelerated emissions performance 

reduction from overfiring, catalyst abrasion, and substrate degradation during typical use. This

perceived performance reduction was manifested in the lower passing threshold for catalytic wood 

heaters in the current U.S. EPA New Source Performance Standards (NSPS). 

It was proposed by the Catalytic Hearth Coalition (CHC) that there are some improved stove 

designs which protect the catalytic combustor from direct flame impingement and subsequent 

degradation of the catalyst/combustor. OMNI Environmental Services, Inc. (OMNI) was 

contracted by the CHC to conduct an independent study on the longevity of wood stove catalytic 

combustors from stoves with improved designs. 

Study Discussion

Two wood heaters with improved designs were selected by the CHC. Lists of owners who 

purchased these heaters were provided by the CHC. OMNI conducted a phone survey and 

randomly selected four used combustors from two age categories, 5-6 years old and 8-9 years old. 

The main criteria were the owner had to follow manufactures instructions for heater use and burn 

more than two cords of wood per year. The used combustors were removed from their original 

heaters, packaged and shipped by the heater owners to OMNI for evaluation. All combustors were 

gently cleaned with a vacuum prior to testing. New and blank (without catalytic wash-coating) 

combustors were provided by the CHC.

Test Methods

All tests were conducted using Douglas fir dimensional lumber and hot starts as is stipulated in 

EPA Method 28/5G. One burn rate (Category 2; 0.8 to 1.25 kg (dry)/h) was selected as a target 

for all tests in the study. It should be emphasized that the emission results reported are from single 

burn rates and are not weighted averages of four burn rates as specified in Method 28. The 

particulate emissions results are reported on a grams of pollutant per time (g/h) basis as 5Hequivilents as is used in Method 28. Additionally, the particulate emissions results are reported on 

a grams of pollutant per mass of fuel burned basis.

Results

Results for the Woodstock Soapstone Co. Fireview 205 and associated combustors are provided in 

Table 1. Results for the Blaze King Inc. Princess PEJ 1006 and associated combustors are 

provided in Table 2. Photographs of the stoves and combustors are provided in Figure 1.

Conclusions

Based on the results, it can be concluded that the four catalytic combustors from the two selected 

stoves, maintained substrate integrity without substantial particulate matter emissions performance 

reduction. Although more testing is needed before conclusive statements can be made about the 

majority of catalytically-equipped wood-fired heaters and their combustors, regulators making 

revisions to wood heater emissions regulations should keep in mind catalytic heater manufactures 

have made substantial improvements to heater design to increase combustor longevity.
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Table 1. Owner Information, Burn Rate and Particulate Emissions for the Woodstock Soapstone Co. 

Fireview 205 (EPA Certified Value of 1.35 g/h)

Test Run 3 Test Run 2 Test Run 4 Test Run 5

Owner

Information

Catalytic

Combustor

New

(aged1)

Used 5.75 

years

Used 8.5 

years

Blank

Fuel Usage (cords/year) na 3 more than 2 na

Testing2 

Characteristic

Burn Rate*

(kg, dry/h) 0.82 0.75 0.88 0.92

Emission 

Rates 

(g/h)

PM**

(5H-equivilent) 1.20 1.34 1.50 7.80

Emission 

Factors 

(g/kg (dry))

PM**

(5H-equivilent) 1.46 1.80 1.71 8.45

1 Combustor aged 50+ hours with cordwood at a medium burn rate as stipulated in EPA Method 28.

2 The fueling protocol for each test followed EPA Method 28/5G (dimensional Douglas fir lumber 19-25%, moisture db). Each test was 

conducted from a hot start as stipulated in EPA Method 28.

db = dry basis

na = not applicable 

*Average wood moisture (dry) for these four tests ranged between 21.4 % and 23.1 %.

** Measured using EPA Method 5G and adjusted to 5H by NSPS conversion: 5H = (1.82) x (5G)0.83
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Table 2. Owner Information, Burn Rate and Particulate Emissions for the Blaze King 

Model: Princess PEJ 1006 (EPA Certified Value of 2.40 g/h)

Test Run 7 Test Run 8 Test Run 9 Test Run 10

Owner

Information

Catalytic

Combustor

New

(aged1)

Used 5.5

years

Used 9

years

Blank

Fuel Usage

(cords/year) na 4 to 6 3 na

Testing2 

Characteristic

Burn Rate*

(kg, dry/h) 0.99 1.10 0.98 1.04

Emission 

Rates 

(g/h)

PM**

(5H-equivilent) 5.26 7.16 6.30 31.95

Emission 

Factors 

(g/kg (dry))

PM**

(5H-equivilent) 5.33 6.53 6.46 30.72

1 Combustor aged 50+ hours with cordwood at a medium burn rate as stipulated in EPA Method 28.

2 The fueling protocol for each test followed EPA Method 28/5G (dimensional Douglas fir lumber 19-25%, moisture db). Each test was 

conducted from a hot start as stipulated in EPA Method 28.

db = dry basis

na = not applicable 

*Average wood moisture (dry) for these four tests ranged between 19.8 % and 22.8 %.

** Measured using EPA Method 5G and adjusted to 5H by NSPS conversion: 5H = (1.82) x (5G)0.83
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Figure 1. Photographs of Stoves and Combustors

Woodstock Soapstone 

Co. Fireview 205

(EPA 1.35 g/h)

Blank

(no wash-coating)

(25 cells per sq. inch)

New

(Aged 50+ h)

Used 5.75 years 

(post vacuuming)

3 cords per year

Used 8 years 

(post vacuuming)

More than 2 cords per year

Blaze King 

Princess PEJ 1006

(EPA 2.40 g/h)

Blank

(no wash-coating)

(16 cells per sq. inch)

New

(Aged 50+ h)

Used 5.5 years 

(post vacuuming)

4-6 cords per year

Used 9 years

(post vacuuming)

3 cords per year