Understanding VOC Levels in an Office: The Impact of Acid-Base and Oxidation Surface Chemistry

JILLIAN DOWNEY, Jonathan Abbatt, University of Toronto

     Abstract Number: 67
     Working Group: Indoor Aerosols

Abstract
Gas-phase volatile organic compounds (VOCs) impact indoor air quality, as some are harmful irritants. Indoor surfaces act as reservoirs for VOCs and, even in the absence of direct VOC sources, VOC gas-phase concentrations are buffered through the emission of compounds stored in these reservoirs. Several factors may influence surface fluxes; for example, surface pH impacts acidic and basic VOC partitioning. Surface pH can be influenced by human activities such as cooking or cleaning that emit ammonia or acetic acid, increasing or decreasing the surface pH, respectively. Additionally, the role of surfaces may be influenced by an indoor oxidant like ozone. In this manner, surfaces not only act as a direct VOC emission source but also as a reactive medium, resulting in the release of oxidized VOCs.

In this work, we investigated how the addition of ammonia and ozone affects the air composition of an office. Painted and glass surfaces were aged in an office, placed in a flux chamber, and the emissions of acidic/basic species were measured using a Vocus PTR-MS. To investigate the role of surface pH, ammonia was introduced into the chamber, and changes in the acidic/basic species were monitored. Pronounced levels of amines and amides are released with ammonia addition. Additionally, to investigate the role of surface emissions and ozonolysis, clean air and ozone-filled air was added to a flux chamber attached to the office wall. VOC emission rates from the flux chamber with and without ozone were compared to ambient VOC levels in the office to assess the contribution of surface flux and ozonolysis to indoor air composition. Overall, this work demonstrates that surfaces play a dominant role in determining indoor VOC concentrations, and that human activities not only affect indoor air quality through direct emissions but also by driving secondary chemical processes.