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A major component of human skin oil is squalene, a highly unsaturated hydrocarbon that protects the skin from atmospheric oxidants. Skin oil, and thus squalene, is continuously replenished on the skin surface. Squalene is also quickly consumed through reactions with ozone and other oxidants. This study examined the extent of squalene depletion in the skin oils of the forearm of human volunteers after exposure to ozone in a climate chamber. Temperature, relative humidity (RH), skin coverage by clothing, and participants' age were varied in a controlled manner. Concentrations of squalene were determined in skin wipe samples collected before and after ozone exposure. Exposures to ozone resulted in statistically significant decreases in post-exposure squalene concentrations compared to pre-exposure squalene concentrations in the skin wipes when squalene concentrations were normalized by concentrations of co-occurring cholesterol but not by co-occurring pyroglutamic acid (PGA). The rate of squalene loss due to ozonolysis was lower than its replenishment on the skin surface. Within the ranges examined, temperature and RH did not significantly affect the difference between normalized squalene levels in post-samples versus pre-samples. Although not statistically significant, skin coverage and age of the volunteers (three young adults, three seniors, and three teenagers) did appear to impact squalene depletion on the skin surfaces.

Humidity plays an important role in the surface removal and concentrations of indoor pollutants such as ozone; however, the indoor surface dynamics and chemistry of organic peroxides is largely unknown. Organic hydroperoxides (ROOHs) are known to participate in the multiphase chemistry of outdoor aerosols and clouds, suggesting that reactive uptake in condensed grime on indoor surfaces is plausible, particularly in humid homes. Here, the effect of relative humidity (RH) on the deposition velocity ( v d ) and reaction probability ( γ ) of a model ROOH to naturally soiled indoor glass surfaces was investigated; specifically, by using authentic isoprene hydroxy hydroperoxide (1,2-ISOPOOH) as the model compound. Glass was soiled in 3 local homes for 1+ years and characterized. The removal of ISOPOOH by soiled and clean glass was measured under 5-6%, 56-58%, and 83-84% RH conditions using a novel flow reactor designed for indoor surfaces coupled to an iodide chemical ionization high-resolution time-of-flight mass spectrometer (I-HR-TOF-CIMS). The v d and γ increased with increasing RH, ranging from 0.001-0.059 cm s -1 and 0.4-4.6 (×10 -6 ), respectively, on soiled glass surfaces. The v d and γ ranged from only 0.001-0.016 cm s -1 and 0.1-0.8 (×10 -6 ), respectively, across RH conditions on clean glass, demonstrating a greater RH effect on soiled materials than clean. Loss rates calculated under humid conditions to soiled glass (∼1-6 h -1 ) were competitive in scale with ventilation rates in typical residences, indicating the importance of surface uptake for indoor ROOH concentrations. This work provides parameters for predictive modeling of indoor ROOHs. To our knowledge, these are the first direct measurements of the v d of an ROOH to naturally soiled indoor surfaces.

Reactive oxygen species (ROS) are among the species thought to be responsible for the adverse health effects of particulate matter (PM) inhalation. Field studies suggest that indoor sources of ROS contribute to measured ROS on PM in indoor air. We hypothesize that ozone reacts on indoor surfaces to form semi-volatile ROS, in particular organic peroxides (OPX), which partition to airborne particles. To test this hypothesis, we modeled ozone-induced formation of OPX, its decay and its partitioning to PM in a residential building and compared the results to field measurements. Simulations indicate that, while ROS of outdoor origin is the primary contributor to indoor ROS (in PM), a substantial fraction of ROS present in indoor PM is from ozone-surface chemistry. At an air change rate equal to 1/h, and an outdoor ozone mixing ratio of 35 ppb, 25% of the ROS concentration in air is due to indoor formation and partitioning of OPX to PM. For the same conditions, but with a modest indoor source of PM (1.5 mg h -1 ), 44% of indoor ROS on PM is of indoor origin. An indoor source of ozone, such as an electrostatic air cleaner, also increases OPX present in indoor PM. The results of the simulations support the hypothesis that ozone-induced formation of OPX on indoor surfaces, and subsequent partitioning to aerosols, is sufficient to explain field observations. Therefore, indoor sourced ROS could contribute meaningfully to total inhaled PM-ROS.

Personal care products are increasingly being marketed to protect skin from the potentially harmful effects of air pollution. Here, we experimentally measure ozone deposition rates to skin and the generation rates and yields of oxidized products from bare skin and skin coated with various lotion formulations. Lotions reduced the ozone flux to the skin surface by 12% to 25%; this may be due to dilution of reactive skin lipids with inert lotion compounds or by reducing ozone diffusivity within the resulting mixture. The yields of volatile squalene oxidation products were 25% to 70% lower for a commercial sunscreen and for a base lotion with an added polymer or with antioxidants. Lower yields are likely due to competitive reactions of ozone with lotion ingredients including some ingredients that are not intended to be ozone sinks. The dynamics of the emissions of squalene ozonation product 6 methyl-2-heptenone (6MHO) suggest that lotions can dramatically reduce the solubility of products in the skin film. While some lotions appear to reduce the rate of oxidation of squalene by ozone, this evidence does not yet demonstrate that the lotions reduce the impact of air pollution on skin health., Competing Interests: The authors have declared that no competing interests exist.

Ozone-initiated oxidation reactions on indoor surfaces meaningfully alter the chemical composition of indoor air and human exposure to air toxins. Ozone mass transport within the indoor surface boundary layer plays a key role in ozone-surface reaction kinetics. However, limited information is available on detailed ozone transport dynamics near realistic, irregular indoor surfaces. This paper presents a research framework to study the underlying mechanisms of ozone reactions with realistic indoor surfaces based on microscope scanning of surface material and detailed Computational Fluid Dynamics (CFD) simulation. The study results show that indoor surface topography can meaningfully affect ozone mass transport within a surface boundary layer, thereby modulating near-surface ozone concentration gradient and surface uptake. The results also reveal that the effective indoor surface area available for ozone reaction varies with indoor air speed and turbulent air mixing within the boundary layer. The detailed dynamic behaviors of ozone reactions with realistic indoor surfaces provide insights into the implications of pollutant-surface interactions on indoor chemistry and air quality.

People influence indoor air chemistry through their chemical emissions via breath and skin. Previous studies showed that direct measurement of total OH reactivity of human emissions matched that calculated from parallel measurements of volatile organic compounds (VOCs) from breath, skin, and the whole body. In this study, we determined, with direct measurements from two independent groups of four adult volunteers, the effect of indoor temperature and humidity, clothing coverage (amount of exposed skin), and indoor ozone concentration on the total OH reactivity of gaseous human emissions. The results show that the measured concentrations of VOCs and ammonia adequately account for the measured total OH reactivity. The total OH reactivity of human emissions was primarily affected by ozone reactions with organic skin-oil constituents and increased with exposed skin surface, higher temperature, and higher humidity. Humans emitted a comparable total mixing ratio of VOCs and ammonia at elevated temperature-low humidity and elevated temperature-high humidity, with relatively low diversity in chemical classes. In contrast, the total OH reactivity increased with higher temperature and higher humidity, with a larger diversity in chemical classes compared to the total mixing ratio. Ozone present, carbonyl compounds were the dominant reactive compounds in all of the reported conditions.

The skin of 20 human participants was exposed to ∼110 ppb O 3 and volatile products of the resulting chemistry were quantified in real time. Yields (ppb product emitted/ppb ozone consumed) for 40 products were quantified. Major products of the primary reaction of ozone-squalene included 6-methyl 5-hepten-2-one (6-MHO) and geranyl acetone (GA) with average yields of 0.22 and 0.16, respectively. Other major products included decanal, methacrolein (or methyl vinyl ketone), nonanal, and butanal. Yields varied widely among participants; summed yields ranged from 0.33 to 0.93. The dynamic increase in emission rates during ozone exposure also varied among participants, possibly indicative of differences in the thickness of the skin lipid layer. Factor analysis indicates that much of the variability among participants is due to factors associated with the relative abundance of (1) "fresh" skin lipid constituents (such as squalene and fatty acids), (2) oxidized skin lipids, and (3) exogenous compounds. This last factor appears to be associated with the presence of oleic and linoleic acids and could be accounted for by uptake of cooking oils or personal care products to skin lipids.

Ozone has adverse effects on human health. Skin oil on the human surface acts as an ozone sink indoors, producing oxidation products that can cause skin and respiratory irritations. Concentrations of ozone and oxidation products near human surfaces, including the breathing zone, can be modulated by indoor ventilation modes and human surface conditions. The objective of this study is to examine concentrations and spatial heterogeneity of ozone and ozonolysis products under representative ranges of indoor ventilation, clothing, and breathing conditions. Using computational fluid dynamics (CFD) simulation in conjunction with a chemical kinetic model, details of ozone reactions with the human surface and subsequent chemical reactions are examined. The results show that primary ozonolysis products are concentrated near the soiled clothing, while the secondary products are relatively well distributed throughout the room. Increasing indoor air mixing enhances the ozone deposition to the human surface, thereby resulting in higher emission rates of oxidation products in the room. Soiled clothing consumes more ozone than clean clothing and accordingly produces ~ 65% more primary products and ~15% more secondary products. The results also reveal that unsaturated hydrocarbons from the human breath, such as isoprene, contribute to only ~0.5% of ozone removal compared to ozone deposition to the human surface., (© 2020 John Wiley & Sons A/S . Published by John Wiley & Sons Ltd.)

Ozone (O 3 ) chemistry is thought to dominate the oxidation of indoor surfaces. We consider the hypothesis that reactions taking place within indoor boundary layers result in greater than anticipated hydroxyl radical (OH) deposition rates. We develop models that account for boundary layer mass-transfer phenomena, O 3 -terpene chemistry and OH formation, removal, and deposition; we solve these analytically and by applying numerical methods. For an O 3 -limonene system, we find that OH flux to a surface with an O 3 reaction probability of 10 -8 is 4.3 × 10 -5 molec/(cm 2 s) which is about 10 times greater than predicted by a traditional boundary layer theory. At very low air exchange rates the OH surface flux can be as much as 10% of that for O 3 . This effect becomes less pronounced for more O 3 -reactive surfaces. Turbulence intensity does not strongly influence the OH concentration gradient except for surfaces with an O 3 reaction probability >10 -4 . Although the O 3 flux dominates OH flux under most conditions, OH flux can be responsible for as much as 10% of total oxidant uptake to otherwise low-reactivity surfaces. Further, OH chemistry differs from that for ozone; therefore, its deposition is important in understanding the chemical evolution of some indoor surfaces and surface films., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

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., (© 2019 The Authors. Indoor Air published by John Wiley & Sons Ltd.)

We report on the development of a modelling consortium for chemistry in indoor environments that connects models over a range of spatial and temporal scales, from molecular to room scales and from sub-nanosecond to days, respectively. Our modeling approaches include molecular dynamics (MD) simulations, kinetic process modeling, gas-phase chemistry modeling, organic aerosol modeling, and computational fluid dynamics (CFD) simulations. These models are applied to investigate ozone reactions with skin and clothing, oxidation of volatile organic compounds and formation of secondary organic aerosols, and mass transport and partitioning of indoor species to surfaces. MD simulations provide molecular pictures of limonene adsorption on SiO2 and ozone interactions with the skin lipid squalene, providing kinetic parameters such as surface accommodation coefficient, desorption lifetime, and bulk diffusivity. These parameters then constrain kinetic process models, which resolve mass transport and chemical reactions in gas and condensed phases for analysis of experimental data. A detailed indoor chemical box model is applied to simulate α-pinene ozonolysis with improved representation of gas-particle partitioning. Application of 2D-volatility basis set reveals that OH-induced aging sometimes drives increases in indoor organic aerosol concentrations, due to organic mass functionalization and enhanced partitioning. CFD simulations show that concentrations of ozone and primary product change near the human surface rapidly, indicating non-uniform spatial distributions from the occupant surface to ambient air, while secondary ozone product is relatively well-mixed throughout the room. This development establishes a framework to integrate different modeling tools and experimental measurements, opening up an avenue for development of comprehensive and integrated models with representations of various chemistry in indoor environments.

Ozone can react homogeneously with unsaturated organic compounds in buildings to generate undesirable products. However, these reactions can also occur on indoor surfaces, especially for low-volatility organics. Conversion rates of ozone with α-terpineol, a representative low-volatility compound, were quantified on surfaces that mimic indoor substrates. Rates were measured for α-terpineol adsorbed to beads of glass, polyvinylchloride (PVC), and dry latex paint, in a plug flow reactor. A newly defined second-order surface reaction rate coefficient, k(2), was derived from the flow reactor model. The value of k(2) ranged from 0.68 × 10(-14) cm(4)s(-1)molecule(-1) for α-terpineol adsorbed to PVC to 3.17 × 10(-14) cm(4)s(-1)molecule(-1) for glass, but was insensitive to relative humidity. Further, k(2) is only weakly influenced by the adsorbed mass but instead appears to be more strongly related to the interfacial activity α-terpineol. The minimum reaction probability ranged from 3.79 × 10(-6) for glass at 20% RH to 6.75 × 10(-5) for PVC at 50% RH. The combination of high equilibrium surface coverage and high reactivity for α-terpineol suggests that surface conversion rates are fast enough to compete with or even overwhelm other removal mechanisms in buildings such as gas-phase conversion and air exchange.

Dynamic gas sampling using solid phase microextraction (SPME) was evaluated for recovery of reactive terpenes and terpenoids in the presence of ozone. For limonene, α-terpineol and dihydromyrcenol in the 20-60 ppb range, this method achieves >80% recovery for ozone mixing ratios up to 100 ppb. Both the experimental results and a model analysis indicate that higher ozone concentrations and longer sampling times result in lower percent recovery. Typically greater than 90% recovery and ppb level method detection limits were achieved with a 5 min sample time. Increasing the flow rate from 100 to 400 sccm flow (5-20 cms(-1)) through the active sampler did not significantly affect sensitivity or recovery in most cases, probably due to negligible mass-transfer improvements. The recovery for each compound improves when sampling from a mixture of different species than that from a single compound sample. This may be due to competition for ozone amongst adsorbed species. Dynamic SPME sampling can improve detection and quantification of terpenes in reactive environments, especially for low vapor pressure (<5 mm Hg at 25°C) compounds that can be adsorbed to ozone scrubbers used in other methods., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Field experiments were conducted in four homes during summerto quantify ozone-induced secondary emission rates (SERs) of aldehydes on indoor surfaces. Four surfaces in each house were examined: living room carpet, living room wall, kitchen floor, and kitchen counter. Upon exposure to ozone for 3 h, formaldehyde and C3-C10 saturated aldehydes, especially nonanal, were emitted as products of ozone-surface reactions. Carpet in newer homes had higher SERs than carpet in older homes. For example, the nonanal SER from the living room carpet was 80 microg m(-2) h(-1) in a 1 year old home, but only 8-20 microg m(-2) h(-1) in two homes that were greater than 10 years old. All kitchen countertops were very reactive and high SERs were observed, especially for nonanal. Product yields from countertops were consistent with the products of ozone reactions with oleic and linoleic esters, common in cooking oils. These findings suggest that carpet surfaces become depleted of reactants as they become oxidized over time. However, countertop surfaces, which are cleaned frequently or become covered in cooking oils, are continuously replenished with reactants. Over time, countertops may become the dominant contributor to indoor concentrations of secondary aldehydes. However, when total surface area is taken into account for the homes assessed, carpet is predicted to be the primary source of secondary emissions, even for older homes.

Ozone-induced formation of aldehydes was studied on the surface and in the gas phase above carpets and on carpet components. Samples of four carpets were exposed to 100 ppb ozone. Emission rates of aldehydes and other organic compounds were measured from exposed and unexposed samples. Surface interactions of ozone with carpets produced C1-C13 n-aldehydes and several unsaturated aldehydes. Total aldehyde emission rates increased markedly with ozone exposure, from 1 to 70 microg m(-2) h(-1) for unexposed samples, to 60-800 microg m(-2) h(-1) during exposure. One exposed sample emitted large amounts of 2-nonenal (180-230 microg m(-2) h(-1)), a compound with a low odor threshold. Material balance modeling of a residence with this high emitting carpet suggests (1) that the concentration of 2-nonenal would be well above its odor threshold even in areas with only moderate ambient ozone levels and (2) that odorous levels of 2-nonenal could persist for years. Reactions of ozone with gas-phase primary emissions from carpet significantly reduced the levels of 4-phenylcyclohexene and produced small amounts of branched ketones. Separately measured patterns of aldehyde emissions from ozone exposure of linseed and tung oils were similar but not identical to those observed from ozone-exposed carpets.

Reactive oxygen species (ROS) are an important contributor to adverse health effects associated with ambient air pollution. Despite infiltration of ROS from outdoors, and possible indoor sources (eg, combustion), there are limited data available on indoor ROS. In this study, part of the second phase of Air Composition and Reactivity from Outdoor aNd Indoor Mixing campaign (ACRONIM‐2), we constructed and deployed an online, continuous, system to measure extracellular gas‐ and particle‐phase ROS during summer in an unoccupied residence in St. Louis, MO, USA. Over a period of one week, we observed that the non‐denuded outdoor ROS (representing particle‐phase ROS and some gas‐phase ROS) concentration ranged from 1 to 4 nmol/m3 (as H2O2). Outdoor concentrations were highest in the afternoon, coincident with peak photochemistry periods. The indoor concentrations of particle‐phase ROS were nearly equal to outdoor concentrations, regardless of window‐opening status or air exchange rates. The indoor/outdoor ratio of non‐denuded ROS (I/OROS) was significantly less than 1 with windows open and even lower with windows closed. Combined, these observations suggest that gas‐phase ROS are efficiently removed by interior building surfaces and that there may be an indoor source of particle‐phase ROS. [ABSTRACT FROM AUTHOR]

With the gradual reduction of emissions from building products, emissions from human occupants become more dominant indoors. The impact of human emissions on indoor air quality is inadequately understood. The aim of the Indoor Chemical Human Emissions and Reactivity (ICHEAR) project was to examine the impact on indoor air chemistry of whole‐body, exhaled, and dermally emitted human bioeffluents under different conditions comprising human factors (t‐shirts/shorts vs long‐sleeve shirts/pants; age: teenagers, young adults, and seniors) and a variety of environmental factors (moderate vs high air temperature; low vs high relative humidity; presence vs absence of ozone). A series of human subject experiments were performed in a well‐controlled stainless steel climate chamber. State‐of‐the‐art measurement technologies were used to quantify the volatile organic compounds emitted by humans and their total OH reactivity; ammonia, nanoparticle, fluorescent biological aerosol particle (FBAP), and microbial emissions; and skin surface chemistry. This paper presents the design of the project, its methodologies, and preliminary results, comparing identical measurements performed with five groups, each composed of 4 volunteers (2 males and 2 females). The volunteers wore identical laundered new clothes and were asked to use the same set of fragrance‐free personal care products. They occupied the ozone‐free (<2 ppb) chamber for 3 hours (morning) and then left for a 10‐min lunch break. Ozone (target concentration in occupied chamber ~35 ppb) was introduced 10 minutes after the volunteers returned to the chamber, and the measurements continued for another 2.5 hours. Under a given ozone condition, relatively small differences were observed in the steady‐state concentrations of geranyl acetone, 6MHO, and 4OPA between the five groups. Larger variability was observed for acetone and isoprene. The absence or presence of ozone significantly influenced the steady‐state concentrations of acetone, geranyl acetone, 6MHO, and 4OPA. Results of replicate experiments demonstrate the robustness of the experiments. Higher repeatability was achieved for dermally emitted compounds and their reaction products than for constituents of exhaled breath. [ABSTRACT FROM AUTHOR]

Abstract: Low volatility terpenoids emitted from consumer products can react with ozone on surfaces and may significantly alter concentrations of ozone, terpenoids and reaction products in indoor air. We measured the reaction probability and a second-order surface-specific reaction rate for the ozonation of dihydromyrcenol, a representative indoor terpenoid, adsorbed onto polyvinylchloride (PVC), glass, and latex paint coated spheres. The reaction probability ranged from (0.06–8.97) × 10−5 and was very sensitive to humidity, substrate and mass adsorbed. The average surface reaction probability is about 10 times greater than that for the gas-phase reaction. The second-order surface-specific rate coefficient ranged from (0.32–7.05) × 10−15 cm4 s−1 molecule−1and was much less sensitive to humidity, substrate, or mass adsorbed. We also measured the ozone deposition velocity due to adsorbed dihydromyrcenol on painted drywall in a room-sized chamber, Based on that, we calculated the rate coefficient ((0.42–1.6) × 10−15 cm4 molecule−1 s−1), which was consistent with that derived from bench-scale experiments for the latex paint under similar conditions. We predict that more than 95% of dihydromyrcenol oxidation takes place on indoor surfaces, rather than in building air. [Copyright &y& Elsevier]

Abstract: A Monte Carlo analysis of indoor ozone levels in four cities was applied to provide guidance to regulatory agencies on setting maximum ozone emission rates from consumer appliances. Measured distributions of air exchange rates, ozone decay rates and outdoor ozone levels at monitoring stations were combined with a steady-state indoor air quality model resulting in emission rate distributions (mg h−1) as a function of % of building hours protected from exceeding a target maximum indoor concentration of 20 ppb. Whole-year, summer and winter results for Elizabeth, NJ, Houston, TX, Windsor, ON, and Los Angeles, CA exhibited strong regional differences, primarily due to differences in air exchange rates. Infiltration of ambient ozone at higher average air exchange rates significantly reduces allowable emission rates, even though air exchange also dilutes emissions from appliances. For Houston, TX and Windsor, ON, which have lower average residential air exchange rates, emission rates ranged from −1.1 to 2.3 mg h−1 for scenarios that protect 80% or more of building hours from experiencing ozone concentrations greater than 20 ppb in summer. For Los Angeles, CA and Elizabeth, NJ, with higher air exchange rates, only negative emission rates were allowable to provide the same level of protection. For the 80th percentile residence, we estimate that an 8-h average limit concentration of 20 ppb would be exceeded, even in the absence of an indoor ozone source, 40 or more days per year in any of the cities analyzed. The negative emission rates emerging from the analysis suggest that only a zero-emission rate standard is prudent for Los Angeles, Elizabeth, NJ and other regions with higher summertime air exchange rates. For regions such as Houston with lower summertime air exchange rates, the higher emission rates would likely increase occupant exposure to the undesirable products of ozone reactions, thus reinforcing the need for zero-emission rate standard. [Copyright &y& Elsevier]

Abstract: Reactive building materials offer an opportunity to provide indoor air cleaning with minimal energy use. Laboratory and test house experiments provide evidence that indoor ozone concentrations can be diminished by activated carbon (AC) and unpainted gypsum wallboard (GWB) panels. These two materials are highly reactive with ozone and produce few byproducts. When measured in a 14.2m3 stainless-steel chamber, the mean deposition velocities to the materials were 5.3m h-1 for AC and 2.4mh−1 for GWB for a variety of airflow and relative humidity conditions. The ozone decay rates for both the materials were also measured in an unoccupied 34.5m3 bedroom under various mixing conditions. In this case, ozone removal increased relative to background by 27–100% with a 4.4m2 panel of a reactive material placed on one wall of the bedroom. The ozone decay rate for the bedroom increased over background by approximately 2–3h−1 for GWB and 2–7h−1 for AC. Application of a mass balance model for a typical home demonstrates that effectiveness for ozone removal depends weakly on the air exchange rate and strongly on the panel material, panel area, and mixing conditions. An ozone removal effectiveness of over 80% is possible with sufficient panel area and positioning that provides elevated air speeds near the panels. [Copyright &y& Elsevier]

In this study, the cumulative ozone uptake, the ozone reaction probability and product yields of volatile aldehydes and ketones were quantified for human scalp hair. Hair was chosen because ozone reacts readily with skin oils and the personal-care products that coat hair. Due to their proximity to the breathing zone, these reactions can influence personal exposure to ozone and its volatile reaction products. Hair samples were collected before and after washing and/or application of personal hair-care products. Samples were exposed to ozone for 24h in a tubular Teflon reactor; ozone consumption rates and product emission rates were quantified. The mean values of integrated ozone uptake, initial and final follicle reaction probability values for eight washed and unwashed samples were, respectively, 5.1±4.4μmolO3 g−1, (13±8)×10−5, and (1.0±1.3)×10−5. Unwashed hair taken close to the scalp exhibited the highest integrated ozone uptake and reaction probability, indicating that scalp oils are responsible for much of the ozone reactivity. Otherwise there was no significant difference between washed and unwashed hair. Compounds (geranyl acetone, 6-methyl-5-hepten-2-one, and decanal) associated with ozone reacting with sebum were observed as secondary products more frequently from unwashed hair than for washed hair and the summed yield of aldehydes ranged from 0.00 to 0.86. Based on reaction probabilities, cumulative ozone uptake and typical sebum generation rates, ozone flux to skin and hair is anticipated to be nearly transport limited, reducing personal exposure to ozone and increasing exposure to reaction products. [Copyright &y& Elsevier]

Abstract: Indoor pollutant mass transport, characterized by the “transport-limited deposition velocity”, v t, is dynamic and measurements of this mass-transfer coefficient can be influenced by changing conditions. We find that for large, but realistic, changes in indoor transport conditions during the sampling period, time-averaged measurements of v t can be in error by 40% or more. Measurements using a highly surface reactive species, such as nitric acid, incur the greatest error. The measurement error incurred for species that are moderately surface reactive, such as ozone, varies depending on the type of surfaces available for deposition. Further, the greater the magnitude and frequency in the fluctuations, the greater the error anticipated from time-averaged measurements of v t. An analysis of continuous flux measurements from field experiments in apartments, a lab and an office suggest that time-averaged measurements of v t will typically be in error by 5–15%. [Copyright &y& Elsevier]

Indoor air pollutant concentrations can be influenced by how rapidly species are transported to and from surfaces. Consequently, a greater understanding of indoor transport phenomena to surfaces improves estimates of human exposure to indoor air pollutants. Here, we introduce two methods of rapidly and directly measuring species fluxes at indoor surfaces, allowing us to evaluate the transport-limited deposition velocity, vt (a mass-transfer coefficient). The deposition velocity sensor (DeVS) method employs a small microbalance coated with a pure hydrocarbon, preferably octadecane. We quantify flux (or evaporation rate) of the hydrocarbon into a room by observing the rate of mass loss on the microbalance. The transport-limited deposition velocity, vt, octadecane, is then obtained by combining the flux with the vapor pressure of the hydrocarbon. Simultaneously, vt, ozone is quantified using the deposition velocity of ozone (DeVO) method, which acts as a standard to calibrate and evaluate DeVS. Specifically, DeVO evaluates ozone transport to surfaces by quantifying the conversion by ozone of nitrite to nitrate on a glass fiber filter. Simultaneous laboratory chamber experiments demonstrates that vt for octadecane and ozone are strongly correlated, with the values for ozone ∼1.5 times greater than that for octadecane. In an office experiments, the DeVS method responds within minutes to step changes in conditions such as occupancy, activities and ventilation. At present, the results are in order-of-magnitude agreement with predicted indoor mass-transfer coefficients. [Copyright &y& Elsevier]

Presents experimental studies on the rate of ozone uptake on carpets. Investigation of ozone reactions with whole carpet, carpet fibers and carpet backing; Decrease of reactivity of material with ozone with increasing cumulative exposure; Exploration of aging phenomenon by relating the reaction probability to the cumulative ozone uptake.

Abstract: Ozone reactions that occur on material surfaces can lead to elevated concentrations of oxidized products in the occupied space of buildings. However, there is little information on the impact of materials at full scale, especially for green building materials. Experiments were completed in a 68 m3 climate-controlled test chamber with three certified green building materials that can cover large areas in buildings: (1) recycled carpet, (2) perlite-based ceiling tile and (3) low-VOC paint and primer on recycled drywall. Ozone deposition velocity and primary and secondary emission rates of C1 to C10 saturated carbonyls were determined for two chamber mixing conditions and three values of relative humidity. A direct comparison was made between ozone deposition velocities and carbonyl yields observed for the same materials analyzed in small (10 L) chambers. Total primary carbonyl emission rates from carpet, ceiling tile and painted drywall ranged from 27 to 120 μg m−2 h−1, 13 to 40 μg m−2 h−1, 3.9 to 42 μg m−2 h−1, respectively. Ozone deposition velocity to these three materials averaged 6.1 m h−1, 2.3 m h−1 and 0.32 m h−1, respectively. Total secondary carbonyl emissions from these materials ranged from 70 to 276 μg m−2 h−1, 0 to 12 μg m−2 h−1, and 0 to 30 μg m−2 h−1, respectively. Carbonyl emissions were determined with a transient approximation, and were found to be in general agreement with those found in the literature. These results suggest that care should be taken when selecting green building materials due to potentially large differences in primary and secondary emissions. [Copyright &y& Elsevier]