Emission Factors for New Certified Residential Wood Heaters

Woodstove change-out programs, which entail the replacement of old uncertified wood heaters with new lower-emitting EPA certified wood heaters, have become a recognized strategy to reduce ambient particulate levels. To assess the benefit of particulate emission reductions affected by change outs, accurate emission factors for new model certified wood heaters are needed. Standards of performance (NSPS) for new residential wood heaters were promulgated February 26, 1988. The standards include test methods and procedures for particulate emission measurement. These test methods and procedures can best be described as “benchmark ” and emission rates obtained from them are only loosely predictive of actual in-home emission factors. Independent of NSPS certification, the U.S. EPA has also compiled emission factors for certified woodstoves in its AP-42 document. The particulate emission factors for cordwood heaters contained in the AP-42 document have not been revised since 1991 and are based on the earliest certified models or their prototypes with most measurements made as part of studies conducted in the late 1980s. Considerable improvements have been made in certified wood heaters and in the last two decades and improvements needed in the certification process have become apparent as well. A review of recent particulate data for certified cordwood heaters with recommendations for revising emission factors and the NSPS test methods to make them more predictive of real-world emissions are provided here