The significance of secondary organic aerosol formation and growth in buildings: experimental and computational evidence

Experiments were conducted in an 11 m3 environmental chamber to investigate secondary particles resulting from homogeneous reactions between ozone and α-pinene. Experimental results indicate that rapid fine particle growth occurs due to homogeneous reactions between ozone and α-pinene, and subsequent gas-to-particle partitioning of the products. A new indoor air quality model was used to predict dynamic particle mass concentrations based on detailed homogeneous chemical mechanisms and partitioning of semi-volatile products to particles. Chamber particle mass concentrations were estimated from measured particle size distributions and were in reasonable agreement with results predicted from the model. Both experimental and model results indicate that secondary particle mass concentrations increase substantially with lower air exchange rates. This is an interesting result, given a continuing trend toward more energy-efficient buildings. Secondary particle mass concentrations are also predicted to increase with lower indoor temperatures, higher outdoor ozone concentrations, higher outdoor particle concentrations, and higher indoor α-pinene emissions rates.