Indoor ozone/human chemistry and ventilation strategies

Indoor Air. 2019 Nov;29(6):913-925. doi: 10.1111/ina.12594. Epub 2019 Sep 15.

Abstract

This study aimed to better understand and quantify the influence of ventilation strategies on occupant-related indoor air chemistry. The oxidation of human skin oil constituents was studied in a continuously ventilated climate chamber at two air exchange rates (1 h-1 and 3 h-1 ) and two initial ozone mixing ratios (30 and 60 ppb). Additional measurements were performed to investigate the effect of intermittent ventilation ("off" followed by "on"). Soiled t-shirts were used to simulate the presence of occupants. A time-of-flight-chemical ionization mass spectrometer (ToF-CIMS) in positive mode using protonated water clusters was used to measure the oxygenated reaction products geranyl acetone, 6-methyl-5-hepten-2-one (6-MHO) and 4-oxopentanal (4-OPA). The measurement data were used in a series of mass balance models accounting for formation and removal processes. Reactions of ozone with squalene occurring on the surface of the t-shirts are mass transport limited; ventilation rate has only a small effect on this surface chemistry. Ozone-squalene reactions on the t-shirts produced gas-phase geranyl acetone, which was subsequently removed almost equally by ventilation and further reaction with ozone. About 70% of gas-phase 6-MHO was produced in surface reactions on the t-shirts, the remainder in secondary gas-phase reactions of ozone with geranyl acetone. 6-MHO was primarily removed by ventilation, while further reaction with ozone was responsible for about a third of its removal. 4-OPA was formed primarily on the surfaces of the shirts (~60%); gas-phase reactions of ozone with geranyl acetone and 6-MHO accounted for ~30% and ~10%, respectively. 4-OPA was removed entirely by ventilation. The results from the intermittent ventilation scenarios showed delayed formation of the reaction products and lower product concentrations compared to continuous ventilation.

Keywords: ToF-CIMS; air exchange rate; indoor environment; oxygenated volatile organic compounds; ozone; squalene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air Pollutants / analysis*
  • Air Pollution, Indoor / analysis*
  • Aldehydes / analysis
  • Built Environment
  • Clothing
  • Environmental Monitoring / methods
  • Humans
  • Ketones / analysis
  • Mass Spectrometry / methods
  • Oxidation-Reduction
  • Ozone / analysis*
  • Skin / chemistry*
  • Terpenes / analysis
  • Ventilation / methods*

Substances

  • Air Pollutants
  • Aldehydes
  • Ketones
  • Terpenes
  • methylheptenone
  • Ozone
  • geranylacetone
  • 4-oxopentanal