Ferguson, Andors & Company 

P.O.Box 678, South Royalton, VT 05068 • 802-763-2339 / 802-419-3799 Fax • facomail@sover.net 

Consultants in Product Development and Regulatory Compliance 

April 30, 2010 

Mr. Gil Wood 

Environmental Engineer 

U.S. Environmental Protection Agency 

Office of Air Quality Planning & Standards (C404-05) 

109 T.W. Alexander Drive 

Research Triangle Park, NC 27709 

Re: Enhanced Certified Wood Heater Database 

Dear Mr. Wood, 

This letter will provide background information regarding the Enhanced Certified Wood Heater 

Database (the “Database”) that the Hearth, Patio and Barbecue Association (“HPBA) has 

complied and provided to EPA and stakeholders interested in EPA’s ongoing review of the New 

Source Performance Standard (“NSPS”) for Residential Wood Heaters (40 CFR Part 60, Subpart 

AAA), As you are aware, HPBA is the principal trade association representing the interests of 

manufacturers, distributors and retailers of wood heaters and other hearth appliances. HPBA has 

a longstanding cooperative relationship with EPA and state regulatory authorities regarding the 

regulation of hearth appliances; one of the highlights of this relationship is the regulatory 

negotiation that resulted in the promulgation of Subpart AAA more than twenty years ago. 

HPBA undertook the Database project in the sprit of that longstanding cooperative relationship. 

The Database project was undertaken to address several obstacles that stood in the way of using 

data available to EPA on certified wood heater performance. First, the list of certified wood and 

pellet heaters posted on the EPA website lists many heater models as separate models that are 

actually the same model, as well as many that are no longer being produced. This has occurred 

for several reasons including company consolidation within the industry as well as certifications 

that are still in effect from models that have ceased production or been replaced by updated 

versions with new certifications. If the certification for a previous model version hadn’t lapsed, 

the older model and newer model could both be on the certified heater list. In other cases, 

companies with certified heater models have simply gone out of business. Addressing these 

issues implicated contacting the manufacturers directly, something HPBA was well positioned to 

do, since most of the manufacturers are HPBA members. Second, once a correct list of the 

current universe of certified appliances was assembled, it would be necessary to match that list 

with the certification test reports applicable to each model. Those data are available, of course, 

in EPA’s files, but the test reports and certification data are not in electronic format. Each test 

report therefore would need to be examined by hand to extract and extract and compile the 

needed information. This would have to be done by EPA and would be a major undertaking. 

HPBA formulated a methodology to assemble a useable database, that had as its objectives the 

culling of the EPA certified heater list down to those heater models that are currently in 

production, and obtaining detailed certification test data and other information that might be 

useful in the NSPS process and that was not included on the EPA website (e.g., the test method 

used for certification testing for each heater model). 
Mr. Gil Wood 

April 30, 2010 

Page 2 of 3 

First, a list of manufacturers/importers of certified wood and pellet heater manufacturers was 

generated from the EPA certified heater list. The list was then examined and corrected to reflect 

situations where company consolidation had occurred. Finally, every possible effort was made 

to obtain up-to-date contact information for each company on the list. It should be noted that in 

some cases, generally for very small or foreign companies, reliable contact information was 

simply not obtainable. 

Second, each manufacturer/importer was sent a form listing each of the certified heater models 

attributed to their company. They were asked to first eliminate obsolete models from their list 

and then to provide detailed information about their currently produced certified models. This 

information included emission data from certification testing, identification of the test method 

used for certification and the certification expiration date. To protect confidentiality, HPBA 

assigned the responsibility of receiving and compiling the data to their in-house statistician. As 

the data arrived, he assigned a model number designation to each dataset in the order received. 

He created a key that would allow only him to know what the actual model and manufacturer 

identity was. This is similar to the process used for gathering other industry statistics (sales data, 

for example) where confidentiality needs to be maintained. 

As data started to arrive, it became apparent that some of the information that was being received 

was incomplete or had potential data quality issues. Additional contact was made with the 

manufacturers to try to improve the data that was being received. In some cases, the follow-up 

was successful and in other cases it was not. 

As a means to insure the quality of the data submissions, an emission data quality check was 

performed for each heater model. This procedure was to calculate the weighted average 

emissions in accordance with EPA Method 28, Section 8.1 using the certification test data that 

were received and comparing the calculated value to the weighted average emissions listed for 

the model by EPA. When discrepancies that were outside of the realm of rounding errors 

(usually 0.1 gram/hour) were detected, the datasets were labeled as having data quality problems. 

HPBA went back to those manufacturers/importers yet again, to try to resolve the data quality 

issues. Again, there were some successes and some failures to resolve the issues. If we could 

not resolve the data quality issues, that fact was noted for the affected models. See the 

discussion of data “color-coding” below. And it should be noted that generally, the datasets with 

quality issues were distributed at the higher emission rates. 

There were two releases of the Database. The first, in December 2009, included datasets that 

had issues that had not been resolved as of the release date. A color-coding system was 

employed to identify those datasets with suspect data, duplicate data or missing data Known fan 

confirmation test runs were also identified. The Database worksheets included a color-code key 

at the top to help the users. As explained on those worksheets, data that was suspect was coded 

green. Generally, suspect data were any datasets that were received that did not result in the 

EPA published weighted average emissions when the data quality check was made. Duplicate 

data was coded orange. Duplication of data was noted when the manufacturer reported multiple 

models that had been approved using the same certification test. This occurs when the same core 

design (“engine”) has different aesthetic “bodies” available with different model numbers, for 
Mr. Gil Wood 

April 30, 2010 

Page 3 of 3 

example. Data sets with missing data were coded yellow. HPBA continued to work to resolve 

these data issues with additional manufacturer follow-ups until it had to finally conclude those 

activities due to diminishing returns relative to the resources being used. The second (and final) 

version of the Database was released in February 2010. Again, a similar color-coding system 

was used to differentiate usable data from unusable data with additional color-coding (pink) used 

to identify where new or corrected data or information had been received and included. The 

second version also noted where model lines, originally thought to be in current production, were 

actually in the obsolete category. These were coded in gray. Again, a color coding key was 

provided at the top of the worksheets to guide the users. The first tab on the Excel worksheet 

includes all data received, regardless of its quality. The second tab on the worksheet, labeled 

“Full Usable Data Final 2.25.10” only includes the datasets where the quality of the emission 

data for each dataset has been confirmed by the quality check calculation. Datasets that didn’t 

pass the QA were excluded from the compilation under this tab. Duplicate datasets and obsolete 

models also were excluded. This is the database that should be used for any analyses that are 

undertaken. The fact that some of these datasets do not include identification of the test method 

used reduces the usefulness of those particular datasets for determination of best demonstrated 

technology but they may still be useful for other purposes (such as evaluating data weighting 

schemes and the implications of varying the number of test runs). 

The final overall result was usable datasets for 15 catalytic wood heaters, 110 non-catalytic wood 

heaters and 22 pellet heaters. Elimination of the datasets without the test method identification 

resulted in a final tally of 15 catalytic wood heaters, 86 non-catalytic wood heaters and 17 pellet 

heaters. 

The information in this letter was prepared by Robert Ferguson of Ferguson, Andors & Company 

at the direction of the Hearth, Patio and Barbecue Association. Ferguson, Andors & Company is 

providing technical consulting services to HPBA. Please contact me if you have any questions 

concerning the methodology used to compile the Database, or need any additional information 

about it. HPBA looks forward to working with you and your staff as EPA moves forward to 

complete its review of Subpart AAA. 

Respectfully submitted, 

Robert W. Ferguson 

Ferguson, Andors & Company 

Consultant for the Hearth, Patio & Barbecue Association