Formation of oxidized gases and secondary organic aerosol from a commercial oxidant-generating electronic air cleaner

Abstract

Airborne virus transmission during the COVID-19 pandemic increased the demand for indoor air cleaners. While some commercial electronic air cleaners could be effective in reducing primary pollutants and inactivating bioaerosol, studies on the formation of secondary products from oxidation chemistry during their use are limited. Here, we measured oxygenated volatile organic compounds (OVOCs) and the chemical composition of particles generated from a hydroxyl radical generator in an office. During operation, enhancements in OVOCs, especially low-molecular-weight organic and inorganic acids, were detected. Rapid increases in particle number and volume concentrations were observed, corresponding to the formation of highly-oxidized secondary organic aerosol (SOA) (O:C ~1.3). The organic mass spectra showed an enhanced signal at m/z 44 (CO2+) and the aerosol evolved with a slope of ~ -1 in the Van Krevelen diagram. These results suggest that organic acids generated during VOC oxidation contributed to particle nucleation and SOA formation. Nitrate, sulfate, and chloride also increased during the oxidation without a corresponding increase in ammonium, suggesting organic nitrate, organic sulfate, and organic chloride formation. As secondary species are reported to have detrimental health effects, further studies are needed to evaluate potential OVOCs and SOA formation from electronic air cleaners in different indoor environments.

Environmentally persistent free radicals in indoor particulate matter, dust, and on surfaces

“…cOH, O 3 ), UV-, ionization-, or chemical-based approaches have recently been increasingly considered for sanitation of indoor air and surfaces as mitigation measures for SARS-CoV-2 transmission. Given the emerging research on the unintended consequences of indoor air puriers or cleaning products, [71][72][73][74][75] studies should consider how an increase in the oxidative capacity of indoor air can induce chemical transformations occurring on PM, dust, and surfaces that may affect indoor EPFR levels and associated multiphase indoor air chemistry.…”

Real-Time Laboratory Measurements of VOC Emissions, Removal Rates, and Byproduct Formation from Consumer-Grade Oxidation-Based Air Cleaners

“…(4) All cleaners tested emit a range of VOCs, including formaldehyde, at least initially. These results are in broad agreement with previous studies of oxidation-based, consumer-grade portable air cleaners 10 and larger-scale air cleaning technologies, 6,24,25 although the present results provide a more comprehensive characterization of the emitted VOCs and oxidation byproducts than in previous work.…”

Emerging investigator series: deposited particles and human lung lining fluid are dynamic, chemically-complex reservoirs leading to thirdhand smoke emissions and exposure

“…For both gas and surface chemical transformations, future controlled oxidation chamber experiments in concert with the THS aging shown here should be used to examine changes in the detailed chemical composition of surface lms and the potential release of gasphase oxidation products aer exposure to common indoor oxidants (e.g., O 3 , HONO) or radicals generated from increasingly prevalent oxidizing air puriers. 110 The likely effect of antioxidants in the surrogate LLF on the chemical composition of LLF off-gassing should also be investigated further.…”