Indoor sources of ultrafine and accumulation mode particles: Size distributions, size-resolved concentrations, and source strengths

Ultrafine (< 100 nm) and accumulation mode ( 0.1-1 mu m) particles were monitored in an occupied suburban house at 5-minute for 37 consecutive months between November 21, 1997 December 31, 2000. Number concentrations for 126 particle from 9.8-947 nm were measured in 259,176 scans. Of 282 activities, 18 were chosen for detailed analysis. These cooking with a gas stove, toasting with electric toasters and toaster ovens, burning candles and incense, and using a powered clothes dryer. Activities leading to increased particle concentrations occurred 17.5% of the time, and accounted for than half the total concentration of ultrafines and about a of the total accumulation mode particles. The average duration of elevated particle concentrations ranged from 20 minutes 3 hours. Combustion of natural gas ( boiling water, gas clothes showed number peaks near 10 nm, while the electric toaster toaster oven had peaks close to 30 nm. More complex cooking burners plus gas oven) produced peaks in the 35-50 nm range. candles and incense resulted in peaks in the 60-nm range. outdoor sources peaked at nearly 70 nm, indicating the of aging in shifting modes to higher diameters. The highest mean number concentrations were due to complex cooking, average number concentrations of 35,000-50,000 cm(-3), to 12,000 cm(-3) outdoors and less than 3500 cm(-3) indoors when no sources were observed. A strong contribution of the gas-powered clothes dryer was also noted ( 30,000 cm(-3)). concentrations due to these combustion events ranged < 1 ( mu m/cm)(3) to nearly 100 ( mu m/cm)(3). Source strengths were for three common cooking types ( boiling water, deep-frying, oven baking, and broiling) and ranged from 5 x 10(12) to x 10(13) particles per cooking event. The detailed concentration size distribution data collected here may be useful for models of indoor air particle concentrations due to indoor sources and infiltration.