Concentration and fate of airborne particles in museums

To investigate the potential soiling hazard to works of posed by the deposition of airborne particles, time resolved measurements were made of the size distribution chemical composition of particles inside and outside three southern California museums. The measured indoor aerosol characteristics agree well with predictions of a mathematical model of indoor aerosol dynamics based on measured outdoor aerosol characteristics and building parameters. At all three sites, the fraction of particles from outdoor air that deposit onto surfaces varies with particle size, ranging from a minimum of 0.1-0.5% for particles having a diameter in the vicinity of 0.15 µm to greater than 90% for particles larger than 20 µm in diameter. Deposition calculations indicate that, at rates determined for the study days, enough elemental (soot) would accumulate on vertical surfaces in the to yield perceptible soiling in as little as 1 year one site to as long as 10-40 years at the other two sites.