### In the September 19, 2009 paper entitled “Evaluation of Method 28 Wood Heater Burn Rates”, three authors from OMNI Environmental Services assess
the “ veracity of the procedure to weigh burn rates and associated particulate
emission rates used for the calcu lation of the overall certification emission rates ”.
The authors conclude that “ a different technique was used to develop the probabilities of a given burn rate for use with the Method 28 test than is actually used in the Method 28 test itself resulting i n the over

- weighing of lower burn
rates and their associated emission rates as measured following the Method 28 procedures.”

I respectfully disagree with both the analysis and the conclusion of this paper for the reasons outlined below.

In coming to this c onclusion, the authors correctly describe the “different techniques” used for ending a test run during (a) AWES sampling in 43 homes, and (b) Method 28 test protocol:

(a) In AWES sampling the test ended when the temperature one foot
above the flue outlet reach ed 100 degrees F 1 

### ;

(b) In the Method 28 protocol, the test ends when the “remaining weight of the test fuel charge is 0.00 Kg (0.0lb).” The authors note that in the Method 28 test protocol, the temperature at the endpoint of the test is substantially above 10 0 degrees F.

In fact, the temperature at the end of every single Method 28 test ever conducted, regardless of burn category, is several hundred degrees more than 100F. The authors attempt to remedy this apparent inconsistency in the end point determinat ion by grafting the amount of time that it would take for the stack temperature to decline to 100F onto a series of sample Method 28 runs. This effectively doubles the duration of the Method 28 tests, and cuts the already low burn rate by half. (See “Eval uation of Method 28 Wood Heater Burn Rates” , pp.

1 In the AWES test, a chimney temperature of over 100 degrees was simply used as a threshold to indicate that the stove was being used (since the sampling equipment was “automated, and no technician was present). In a study in Klamath Falls/Portland Oregon in 1998

- 99, a similar methodology was used and some stoves never reached 100 degrees, because they were operated continuously and the test p eriod (168 hours, or one full week) ended without stack temperatures ever dropping to 100 degrees. Other stoves dropped to 100 degrees and were restarted, with the total test time below 200 degrees still a small percentage of total test time.
The OMNI au thors admit, "one test cycle may consist of multiple fuel loads."

### 9

- 15) The authors then posit that since the burn rates with the artificial grafts are
well below “real

- world” averages, the weighting must be incorrect (i.e. “overweighting of lower burn rates”).

What the a uthors fail to mention is that the AWES sampling was approximately one week long (168 hours) and the cool down period in the AWES sampling represented a small fraction (5%, more or less) of the total test time, if any time at all (see footnote 1) whereas i n the Method 28 Testing (5

- 6 hours) the same cool down period, when grafted onto the test results, represents
over 50% of the test time.

A more reasonable approach to reconciling this apparent discrepancy would be to artificially graft on an additional 5 % duration to the Method 28 Tests, rather then the 50%+ that the authors erroneously add. Alternatively , maybe the Method 28 burn rates need to be adjusted upward by 5%, more or less, to account for distinction between the 100F and zero mass endpoints.

To understand why the conclusion of this paper is in error, one can look at the Klamath Falls/Portland Oregon Study conducted by EPA in 1998

- 1999. 2 

### In this study, 16 stoves were operated over 5,488 hours and 5,802 kgs (12,764 lbs)
of wood were burned. Th e average burn rate was 1.1 kg/hr. The average stack temperature for the 5,488 hours of testing was over 400 degrees F, which is consistent with the idea that the period of time when the stoves were idling down
to a 100

- degree stack temperature was small.

Current Category 1 and Category 2 burn rates in Method 28 are reasonable slices of typical low burns. The zero

- mass endpoint rule is not a bad way to approximate the burn rates seen in the long multiple

- load AES test with its 100F endpoint rule; the add ition of a cool

- down tail to a two to four

- hour test (see “Evaluation of Method 28 Wood Heater Burn Rates”, page 9 ) is a terrible (and misleading) way to adjust for this difference. To discount the accuracy, usefulness and weighting based on the fact tha t a 168

- hour field test (AWES Sampling) and a 6

- 8 hour lab test (Method 28) have different end points is an

error.

On a related note: The Sept 9 ASTM draft proposes to do away with the Category 1 burn (see 9.5.1) and increase (but not decrease) the amount of start

- up air (see 9.5.5.4), both of which would push the test protocol away from actual “in

- home” burn rates.

2 “Evaluation of Method 28 Wood Heater Burn Rates” indicates that raw data from original studies in VT, NY and OR are no longer available. . However, Paul Tiegs at OMNI indicated that the original tests were “weeks long” and used the same equipment as the Klamath study. In this sense the Klamath study may be representative.

### ADDENDUM 1 

### The current (May 22, 2009) EPA list of certified woodstoves consists of
approximately 657 certified designs (after deleting duplicate listings for the

same stove under multiple company names). The 657 total consists of 432

non

- catalytic certifications, and 225 catalytic certifications.

Of the non

- catalytic certifications 190 (44%) were certified with a low
output of less than 0.8 kg/hr (the current standard for a low burn). 95% of non

catalytic stoves (412 of 432) had a low burn of less than 0

. 9 kg/hr.
Of the catalytic certifications 183 (81%) were certified with a low output of
less than 0.8 kg/hr (the current standard for a low burn). 92% of non

- catalytic
stoves (412 of 432) had a low burn of less than 0

. 9 kg/hr.

Grea ter than 98% of all stoves had a burn rate of less than 1.00 kg/hr.
Only two stoves (both catalytic) had a low burn rate of greater than 1.06 kg/hr.



## Low Burn: Non

- Catalytic Certifications

Burn Rate (Kg/hr) Adjusted Particulate
Emissions 0

- .49 .50

- .59 .60

- .69 .70

- .79 .80

- .89 .90

- .99 1.00+ Total
0.00

- 3.00 2 3 5 27 37 3 0 77
3.01

- 4.0 0 2 13 33 60 0 2 110
4.01

- 5.0 0 0 14 21 59 1 0 95

5.01+ 5 8 24 33 66 10 4 150
TOTAL 7 13 56 114 222 14 6 432
1.6% 3.0% 13.0% 26.4% 51.4% 3.2% 1.4% 100.0% 

### Data from May 22, 2009 EPA list



## Low Burn: Catalytic Certifications

Burn Rate (Kg/hr) Adjusted Particulate
Emissions 0

- .49 .50

- .59 .60

- .69 .70

- .79 .80

- .89 .90

- .99 1.00+ Total
0.00

- 3.00 10 18 24 45 12 2 2 113
3.01

- 4.0 4 9 25 21 6 9 3 77
4.01

- 5.0 2 3 5 9 3 0 1 23
5.01+ 1 1 3 3 2 2 12
TOTAL 17 31 57 78 23 13 6 225
7.6% 13.8% 25.3% 34.7% 10.2% 5.8% 2.7% 100.0% 

### Data from May 22, 2009 EPA list