Although people in developed nations spend up to 90% of their time indoors, 1,2 the chemistry and composition of indoor air remain understudied, especially compared to the outdoor environment. 3 Evaluating air quality in residential dwellings is particularly important for several reasons. First, although building standards (eg, for minimum air change rates and moisture control) have been established over the past several decades, 4,5 many residential structures fail to meet these standards, especially older buildings. Newer buildings, designed to minimize outdoor-to-indoor infiltration for improved energy efficiency, often have higher concentrations of airborne pollutants that are released indoors from materials and activities. 6,7 Concentrations and composition AbstractThe air composition and reactivity from outdoor and indoor mixing field campaign was conducted to investigate the impacts of natural ventilation (ie, window opening and closing) on indoor air quality. In this study, a thermal desorption aerosol gas chromatograph (TAG) obtained measurements of indoor particle-and gas-phase semi-and intermediately volatile organic compounds both inside and outside a single-family test home. Together with measurements from a suite of instruments, we use TAG data to evaluate changes in indoor particles and gases at three natural ventilation periods. Positive matrix factorization was performed on TAG and adsorbent tube data to explore five distinct chemical and physical processes occurring in the indoor environment. Outdoor-to-indoor transport is observed for sulfate, isoprene epoxydiols, polycyclic aromatic hydrocarbons, and heavy alkanes. Dilution of indoor species is observed for volatile, non-reactive species including methylcyclohexane and decamethylcyclopentasiloxane. Window opening drives enhanced emissions of semi-and intermediately volatile species including TXIB, DEET, diethyl phthalate, and carvone from indoor surfaces. Formation via enhanced oxidation was observed for nonanal and 2-decanone when outdoor oxidants entered the home. Finally, oxidative depletion of gas-phase terpenes (eg, limonene and α-pinene) was anticipated but not observed due to limited measurement resolution and dynamically changing conditions. K E Y W O R D Sfield measurements, gas chromatography-mass spectrometry, gas-particle partitioning, natural ventilation, residential air quality, semivolatile organic compounds

Many studies have reported consistent associations between exposure to particulate matter (PM) and cardiovascular and respiratory diseases, neurodegenerative disorders, cancer, premature mortality, and morbidity. [1][2][3][4][5][6][7][8][9][10] Since even low levels of ambient PM can cause detrimental health effects, investigators have attempted to identify the primary cause of PM toxicity. Chemical composition and biologically active chemical species of PM are considered to be more important contributors to the health effects than particle mass concentration by itself. [11][12][13] Levels of reactive oxygen species (ROS) may be a major factor in the health effects associated with PM exposure. [14][15][16][17][18][19][20][21] Reactive oxygen species (ROS) are relatively unstable oxygen-containing radicals and non-radicals. Biologically relevant ROS include superoxide (O 2 •−), hydroxyl (HO • ), hydroperoxyl (HOO • ), and alkylperoxyl (ROO • ) radicals as well as non-radicals such as hydrogen peroxide (H 2 O 2 ), organic peroxides (ROOR), hypochlorite (OCl − ), and peroxynitrite (ONOO − ). 22,23 Reactive oxygen species can be generated in human cells (endogenously) through aerobic metabolism and other biochemical reactions. [24][25][26][27][28][29][30][31][32][33] In addition to endogenous formation of ROS, there are several exogenous sources such as air pollution, food, drugs, heavy metals, organic solvents, and pesticides which have the potential to

The use of facemasks is proven to mitigate the spread of the coronavirus and other biological agents that cause disease. Various forms of facemasks, made using different materials, are being used extensively, and it is important to determine their performance characteristics. The size-dependent filtration efficiency and breathing resistance of household sterilization wrap fabrics, and isolation media (American Society for Testing and Materials (ASTM)- and non-ASTM-rated), were measured in filter-holder- and mannequin-in-chamber-based systems, focusing on particles sizes between 20 nm and 2 μm. Double-layer MERV-14 (Minimum Efficiency Reporting Values with rating 14) showed the highest filtration efficiency (94.9–73.3%) amongst household filter media, whereas ASTM-rated isolation masks showed the highest filtration efficiencies (95.6–88.7) amongst all the masks considered. Filtration efficiency of 3D-printed masks with replaceable filter media was found to depend on the degree of sealing around the media holder, which depended on the material’s compressibility. Filtration efficiencies of triple-layer combinations (95.8–85.3%) follow a profile similar to single layers but with improved filtration efficiencies.

ObjectiveThe COVID-19 pandemic has precipitated widespread shortages of filtering facepiece respirators (FFRs) and the creation and sharing of proposed substitutes (novel designs, repurposed materials) with limited testing against regulatory standards. We aimed to categorically test the efficacy and fit of potential N95 respirator substitutes using protocols that can be replicated in university laboratories.SettingAcademic medical centre with occupational health-supervised fit testing along with laboratory studies.ParticipantsSeven adult volunteers who passed quantitative fit testing for small-sized (n=2) and regular-sized (n=5) commercial N95 respirators.MethodsFive open-source potential N95 respirator substitutes were evaluated and compared with commercial National Institute for Occupational Safety and Health (NIOSH)-approved N95 respirators as controls. Fit testing using the 7-minute standardised Occupational Safety and Health Administration fit test was performed. In addition, protocols that can be performed in university laboratories for materials testing (filtration efficiency, air resistance and fluid resistance) were developed to evaluate alternate filtration materials.ResultsAmong five open-source, improvised substitutes evaluated in this study, only one (which included a commercial elastomeric mask and commercial HEPA filter) passed a standard quantitative fit test. The four alternative materials evaluated for filtration efficiency (67%–89%) failed to meet the 95% threshold at a face velocity (7.6 cm/s) equivalent to that of a NIOSH particle filtration test for the control N95 FFR. In addition, for all but one material, the small surface area of two 3D-printed substitutes resulted in air resistance that was above the maximum in the NIOSH standard.ConclusionsTesting protocols such as those described here are essential to evaluate proposed improvised respiratory protection substitutes, and our testing platform could be replicated by teams with similar cross-disciplinary research capacity. Healthcare professionals should be cautious of claims associated with improvised respirators when suggested as FFR substitutes.

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