SECONDARY ORGANIC AEROSOLS GENERATED BY INDOOR CHEMISTRY: EFFECTS OF CONDITIONED AIR RECIRCULATION RATES

Abstract

Numerous investigators have documented increases in the concentrations of airborne particles as a consequence of ozone/terpene reactions in indoor environments. This study examines the effect of recirculation rates of conditioned air on the concentrations of secondary organic aerosols (SOA) resulting from reactions between indoor limonene and ozone. The experiments were conducted in a large environmental chamber using four recirculation rates (11, 14, 19 and 24 ACH) in combination with a constant outdoor air exchange rate (1 ACH) as well as constant emission rates for limonene and ozone. As the recirculation rate increased, the surface removal rate of both ozone and SOA increased. Due to both of these factors -- the lower ozone concentrations and the larger surface removal rates for particles -- the number- and mass-concentrations of particles in different size-ranges decreased significantly at higher recirculation rates. The size-distribution of the particle number-concentration (less so the particle mass-concentration) also changed with changing recirculation rates, shifting towards larger particles and a broader spread in the distribution at larger recirculation rates. The results have health implications since particle size determine to some extent where a particle deposits in the respiratory tract.