Assessing VOC Emission Rates from an Indoor Surface Using a Flux Chamber and PTR-MS

HAN N. HUYNH, Jenna Ditto, Jie Yu, Michael Link, Dustin Poppendieck, Delphine K. Farmer, Marina Vance, Jonathan Abbatt, University of Toronto

     Abstract Number: 328
     Working Group: Indoor Aerosols

Abstract
Chemical Assessment of Surfaces and Air (CASA) was a 6-week field campaign at the NIST Net-Zero Energy Residential Test FAcility (NZERTF) in March and April of 2022. The campaign focused on the behavior of chemical species in an unoccupied single-family home with continuous gas and aerosol measurements across a suite of instruments. Multiple experiments were conducted to examine the effects of different events (e.g., relative humidity changes, cooking, smoke injection) on indoor air, particles, and surfaces. Our team performed continuous ambient gas-phase measurements using a gas chromatograph (GC) inlet coupled to our Vocus PTR-ToF-MS. In addition, we set up a stainless-steel chamber for measuring gas fluxes from a painted surface inside the test facility. The sampled painted surface was located within two meters of the ambient indoor inlet of the GC-Vocus PTR-ToF-MS. The goal was to speciate and quantify volatile organic compounds (VOCs) fluxing from an indoor surface throughout the campaign, and to see how the VOC surface fluxes correlated with different perturbations in the house. We also determined how the molecular emission rates from the painted surface compared to the total emission rates in the house.

In general, we observed that the VOC surface fluxes throughout the campaign were not strongly impacted by perturbations to the test facility, indicating that the VOCs most likely came from the large surface reservoir underneath the painted surface instead of being introduced for the first time into the house during the CASA campaign. For all calibrated VOCs, we calculated comparable campaign-averaged VOC emission rates measured using the painted surface flux chamber measurements and calculated from the steady-state ambient measurements and total air change rate, when accounting for the total area of painted surfaces in the house. As well, during a zero-mechanical ventilation day, we were able to assess the whole house VOC emission rates using the ambient measurements. We get agreement within a few orders of magnitude between these three emission estimates, supporting the hypothesis that the house surfaces have equilibrated over a long period with VOCs constantly fluxing out at a relatively constant rate. Future experiments are required to assess whether VOC fluxes from a wide variety of types of indoor surface in other residential (e.g., occupied home) and commercial settings would yield similar results.