Indoor Air Pollution Due to Emissions from Unvented Gas-Fired Space Heaters

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Abstract
Operation of an unvented combustion appliance indoors can elevate pollutant concentrations Under laboratory conditions, oxygen consumption rates and pollutant emission rates of CO, CO2, NO, NO2, HCHO and submicron suspended particles emitted from eight unvented gas-fired space heaters operated with well adjusted air shutters at partial and full fuel consumption rates were determined in a 27-m3 chamber. Emission rates were also determined for some heaters operating under poorly tuned conditions. Four of the eight heaters were subsequently tested in a 240-m3 research house with 0.36-1.14 air changes per hour. Based on measurements near steady state, steady state pollutant and oxygen levels were projected: 1930-11,100 ppm for CO2, 1.0-26 ppm for CO (under well-tuned conditions), 0.40-1.46 ppm for NO2, and 19.1-20.7% for O2. Concentrations of CO2, CO, and NO2 sometimes exceeded outdoor or occupational guidelines. Analysis showed that CO, NO, and NO2 emission rates can vary with time and that, while short-term emission rates derived from laboratory tests were consistent with initial emission rates observed in the field, they did not always correspond to steady state emission rates.