Understanding Key Oxidant and RO₂ Regime Combinations in Indoor Spaces

ISABEL ALBORES, Hannah Kenagy, Jesse Kroll, MIT

     Abstract Number: 496
     Working Group: Aerosol Chemistry

Abstract
Indoor oxidation chemistry differs markedly from that of the outdoors due to lower UV levels, reduced ventilation, and distinct chemical sources. Despite this, many studies of indoor oxidation processes rely on experiments or parameterizations aimed at simulating outdoor ambient air. A key chemical distinction is the initiating oxidant: indoor air chemistry is often initiated by ozone (O₃), though hydroxyl radicals (OH) can also contribute, with key sources including alkene ozonolysis and interventions such as air cleaners or germicidal UV (222 nm) lights. The fate of peroxy radicals (RO₂₂ regimes in indoor environments, based on past measurements and modeling. We also use the Framework for 0-Dimensional Atmospheric Modeling (F0AM) to probe the full range of RO₂ fates in indoor environments, informing chamber experiments aimed at simulating indoor conditions. Experiments focused on limonene were performed in a 7.5 m³ Teflon chamber, using mixtures of O₃, OH precursors, and NO_x to probe relevant oxidant and RO₂ regimes. A chemical ionization mass spectrometer (CIMS) and an aerosol mass spectrometer (AMS) measured gas and particle-phase oxidation products. We examine formation of SOA and other products under these conditions, comparing with those of previous chamber experiments centered on simulating outdoor conditions.