Development and validation of a partial flow dilution system for in-situ measurement of residential wood heating appliance PM emission rates using a TEOM™

Measurements of in-situ residential wood heater particulate matter (PM) emissions are needed to assess the efficacy of wood stove changeout programs and changes in appliance performance over time. They can also inform development of State Implementation Plans (SIPs) that must demonstrate how they will meet national PM standards by statutory deadlines. To assess differences in PM emissions between idealized laboratory testing and in-situ use, we developed a partial flow dilution system that matches key dilution tunnel characteristics to ensure that the condensation dynamics of semi-volatile organics in the diluter are similar to the dilution tunnel. Commercial dilution systems were evaluated but did not effectively condense semi-volatiles. A modular diluter design provides dilution factors (DFs) from 5 to 50 and residence times from 0.5 to 5 seconds. DFs were validated via flow measurements, and no trace gas measurements were needed. A TEOM™ is used for stack PM measurements to account for varying stack flow. Diluter performance was assessed by direct comparison to dilution tunnel PM emission rate measurements for four test runs on a cordwood stove using an Integrated Duty Cycle (IDC) Operation and Fueling protocol, with agreement within 25% across four test runs. The average of the four runs was different by 17%. Field performance was evaluated by eight days of testing in a home in Vermont, followed by technology transfer pilot testing in a home in Alaska. Generally good agreement was observed for stove PM emissions, with the diluter design being effective at condensing semi-volatile aerosols from cordwood stoves.