Observing ozone chemistry in an occupied residence

Because people spend most of their time indoors, much of their exposure to ozone occurs in buildings, which are partially protective against outdoor ozone. Measurements in approximately 2000 indoor environments (residences, schools, and offices) show a central tendency for average indoor ozone concentration of 4-6 ppb and an indoor to outdoor concentration ratio of about 25%. Considerable variability in this ratio exists among buildings, as influenced by seven building-associated factors: ozone removal in mechanical ventilation systems, ozone penetration through the building envelope, air-change rates, ozone loss rate on fixed indoor surfaces, ozone loss rate on human occupants, ozone loss by homogeneous reaction with nitrogen oxides, and ozone loss by reaction with gas-phase organics. Among these, the most important are air-change rates, ozone loss rate on fixed indoor surfaces, and, in densely occupied spaces, ozone loss rate on human occupants. Although most indoor ozone originates outdoors and enters with ventilation air, indoor emission sources can materially increase indoor ozone concentrations. Mitigation technologies to reduce indoor ozone concentrations are available or are being investigated. The most mature of these technologies, activated carbon filtration of mechanical ventilation supply air, shows a high modeled health-benefit to cost ratio when applied in densely occupied spaces.

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“…Liu et al 56 reported a similar finding from a detailed investigation of ozone-initiated chemistry in a normally occupied residence.…”

Section: Ozone Loss-rate Coefficient On Human Occupants (K H )supporting

confidence: 52%

Indoor ozone: Concentrations and influencing factors

2021

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“…39 Liu et al have also showed that low ozone concentrations (~4 ppb) can generate detectable increases in multiple VOCs in a normally occupied residence, presumably because of ozonolysis of skin oil and surface films. 63 Along with 6-MHO and 4-OPA, they identified production of octanal, nonenal, nonanal, decanal, undecanal, and dodecanal, which together accounted for ≥12% of the consumed in- Declining per person emission rates of siloxanes were previously reported in a monitoring study conducted in a university classroom. 42 With respect to modeling indoor VOC emissions, time-dependent…”

Section: Emissions From Occupancymentioning

confidence: 75%

Volatile organic compound emissions during HOMEChem

et al. 2021

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Quantifying speciated concentrations and emissions of volatile organic compounds (VOCs) is critical to understanding the processes that control indoor VOC dynamics, airborne chemistry, and human exposures. Here, we present source strength profiles from the HOMEChem study, quantifying speciated VOC emissions from scripted experiments (with multiple replicates) of cooking, cleaning, and human occupancy and from unperturbed baseline measurements of the building and its contents. Measurements using a proton transfer reaction time‐of‐flight mass spectrometer were combined with tracer‐based determinations of air‐change rates to enable mass‐balance‐based calculations of speciated, time‐resolved VOC source strengths. The building and its contents were the dominant emission source into the house, with large emissions of acetic acid, methanol, and formic acid. Cooking emissions were greater than cleaning emissions and were dominated by ethanol. Bleach cleaning generated high emissions of chlorinated compounds, whereas natural product cleaning emitted predominantly terpenoids. Occupancy experiments showed large emissions of siloxanes from personal care products in the morning, with much lower emissions in the afternoon. From these results, VOC emissions were simulated for a hypothetical 24‐h period, showing that emissions from the house and its contents make up nearly half of total indoor VOC emissions.

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“…Furthermore, skin oils and their chemical constituents can be found on various indoor surfaces, such as glass, carpet and settled dusts. 66,67 NCA formation from human-ozone interaction may therefore be substantially more pronounced in real indoor…”

Section: Implications and Future Outlookmentioning

confidence: 99%

Ozone Initiates Human-Derived Emission of Nanocluster Aerosols

Shen

Licina

Weschler

et al. 2021

Environ. Sci. Technol.

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Nanocluster aerosols (NCA, particles <3nm) are important players in driving climate feedbacks and processes that impact human health. This study reports, for the first time, NCA formation when gas-phase ozone reacts with human surfaces. In an occupied climatecontrolled chamber, we detected NCA only when ozone was present. NCA emissions were dependent on clothing coverage, occupant age, air temperature and humidity. Ozoneinitiated chemistry with human skin lipids (particularly their primary surface reaction products) is the key mechanism driving NCA emissions, as evidenced by positive correlations with squalene in human skin wipe samples and known gaseous products from ozonolysis of skin lipids. Oxidation by OH radicals, autoxidation reactions, and humanemitted NH 3 may also play a role in NCA formation. Such chemical processes are anticipated to generate aerosols of the smallest size (1.18-1.55 nm), whereas larger clusters result from subsequent growth of the smaller aerosols. This study shows that whenever we encounter ozone indoors, where we spend most of our lives, nanocluster aerosols will be produced in the air around us. SynopsisChamber studies reveal nanocluster aerosol emissions from ozone-human chemistry occurring in indoor air and the potential formation mechanisms.

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Observing ozone chemistry in an occupied residence

Cited by 77 publications

References 50 publications

Indoor ozone: Concentrations and influencing factors

Indoor ozone: Concentrations and influencing factors

Volatile organic compound emissions during HOMEChem

Ozone Initiates Human-Derived Emission of Nanocluster Aerosols

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