Particle Generation in HVAC Systems due to Ozone/Terpene Reactions
National Science Foundation
Secondary organic aerosols (SOA) are generated indoors because of terpenoids ozonolysis, potentially from both gas phase reactions and surface reactions. Studies have investigated the amount of SOA formation indoors due to reactions in occupied space yet no study has examined SOA contribution from HVAC systems. To investigate the magnitude of this formation, plug-flow and mixing equations were developed to predict steady state ozone, d-limonene, and SOA concentrations within an HVAC system. The model considers return air species that are mixed with outdoor air species in an air handling unit, which are transported via the supply duct to the occupied space. SOA formation was separately accounted for due to both gas- and surface-phase reactions, using experimental data on surface-initiated SOA formation due to ozone reactions with sorbed d-limonene from earlier research. The SOA equations use the ‘volatility basis set’ to determine aerosol mass fractions, which parameterize the strength of the formation.Key parameters such as temperature, air exchange rate, outdoor organic compound concentrations are considered.