The Influence of HVAC Systems on Indoor Secondary Organic Aerosol Formation

Chemical reactions between ozone and terpenoids can yield secondary organic aerosol (SOA), which are potentially a large source of indoor particles that are harmful to human health. The mass of SOA formed in a building is influenced by the operation of the heating, ventilation, and air-conditioning (HVAC) system. This investigation models the influence of HVAC systems on SOA concentrations in residential and commercial buildings. A parametric analysis explores the role of ventilation and recirculation rates, filtration efficiency and loading, and the operation of heat exchangers. In a rural setting, the median residential and commercial SOA concentrations for all simulations were 17.4 μg/m3 (1.09 × 10–9 lb/ft3), with a range of 2.47 to 27.0 μg/m3 (1.54 × 10–10 – 1.68 × 10–9 lb/ft3), and 10.6 μg/m3 (6.61 × 10–10 lb/ft3), with a range of 1.81 to 26.3 μg/m3 (1.13 × 10–10 – 1.64 × 10–9 lb/ft3), respectively. In an urban setting, the median predicted residential and commercial SOA concentrations were 68.0 μg/m3 (4.24 × 10–9 lb/ft3), with a range of 14.7 to 108 μg/m3 (9.17 × 10–10 – 6.74 × 10–9 lb/ft3), and 44.8 μg/m3 (2.80 × 10–9 lb/ft3), with a range of 11.6 to 105 μg/m3 (7.24 × 10–10 – 6.55 × 10–9 lb/ft3), respectively. The most influential HVAC parameters are the flow rates through the system, particle filtration efficiency, and indoor temperature for the residential and commercial models, as well as ozone removal on used filters for the commercial model. The results presented herein can be used to estimate the effects of altering HVAC system components and operation strategies on indoor SOA concentrations and subsequent exposure.

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