Adventures in masonry stove testing from 1988 to 2017

by Norbert Senf, 

Chair of the Masonry Heater Association Technical Committee

Left to right: Mark Champion (in his 
VT test lab), Boris Kukolj (Tulikivi), 

Chris Prior (MHA President), Norbert 

Senf (blog author)  and Jean Francois 

Vachon (soapstone stove builder). 
Photo credit: Mark Seymour.

EPA started regulating wood burning stoves for particulate (PM) emissions in 1988. Regulation was limited to airtight heating stoves. Masonry heaters were not regulated, the stated reason being that they were likely to be clean burning.

In Europe, only carbon monoxide (CO) emissions were regulated. CO is easy to measure, however PM can be very tricky. Wood smoke includes  compounds that will only be captured by a filter if you cool them down and condense them. This is done in the laboratory by mixing them with air in a dilution tunnel, and this is thought to simulate what happens in the ambient air in the real world.

State and county air quality authorities soon started to address wood smoke, and would often pass a generic local regulation that banned all appliances except those that were EPA certified. We, the fledgling Masonry Heater Association (MHA), decided to seek EPA certification.

Although we "knew" that masonry heaters were cleaner even than EPA stoves, nobody had ever measured the PM on one with the dilution tunnel method. With funding help from the Wood Heating Alliance (now HPBA), we were able to participate in a $100,000.00 test method development project for masonry fireplaces and masonry heaters. The project took place at Virginia Polytechnic Institute (VPI) in 1989 and was headed by Dr. Dennis Jaasma.

The results were interesting, with some surprises. EPA did not accept the proposed test method. We immediately realized that we needed do a lot more testing,  and that we would need to develop the capability to do it ourselves.

We were fortunate in being able to arrange for training with OMNI-Test, one of the leading EPA-accredited certification testing laboratories, then and now. OMNI developed a training session for us that took place in September 1996. It included presentations by regulators, an emission chemistry expert (Dr. Jim Houck),  and laboratory testing personnel. Dr. Stockton (Skip) Barnett showed us the low cost portable dilution tunnel that he invented, known as the Condar. He developed it while working for the Condar Company. It was widely used at the time by the major stove manufacturers for in-house testing to develop their certified  stoves.

The attached Powerpoint, Repeatability of Cordwood Combustion Particulate Measurements,  presents a summary of the work we have done at the Masonry Heater Association to calibrate the Condar against the EPA Method 5G laboratory dilution tunnel. It includes a close look at the PM testing repeatability issues,  a major discussion point over the years. We have recently completed 2 cordwood studies, using very carefully matched loads in a masonry heater. Repeatability was within plus or minus 15% - 25%, depending on the ignition method. With crib fueling, we were able to get within 10% repeatability on PM, and within 1.5% repeatability on CO.