Outdoor Ozone Concentrations Research Articles

Rethinking building envelope design: Machine learning approaches to evaluate its impact on indoor ozone exposures

Ozone is widely recognized as an ambient air contaminant that causes acute and chronic health effects. However, there is a limited number of studies investigating indoor exposures to ozone in occupied houses and linking design variables to the predictive power of indoor ozone levels. This study focuses on typical envelope airflow paths used in residences in the Philadelphia area in the United States. The model development draws from the field data, including indoor and outdoor ozone concentration, environmental parameters, and building characteristics from four building envelopes. Five machine learning algorithms (i.e., support vector machine, lasso regression, random forest, Bayesian bridge regression, and gradient boosting) are employed, with indoor ozone concentration as the dependent variable, as it indicates how the hot and sunny weather that might lead to the possibility of indoor air quality (IAQ) alerts due to ozone. The results showed that gradient boosting model based on all field measurements had the highest R-squared value of 0.974 and low enough root mean square error (RMSE) and mean absolute error (MAE) which are 1.182 and 0.788, respectively. We conclude that indoor ozone forecasting model based on inputting environmental survey (ES) in addition to either design variables or indoor environment characteristics can effectively predict and can therefore be used at the building design phase to improve healthy living environments.

Health Impacts of Surface Ozone in Outdoor and Indoor Environments of Hattar Industrial Units, KPK, Pakistan

This research was carried out to analyze variations in indoor and outdoor ozone concentrations and their health impact on local communities of megacities in Pakistan. For indoor ozone measurements, industrial units of an economic zone, Hattar Industrial Estate, Haripur, KPK, Pakistan, were selected. For outdoor ozone measurements, maximum and minimum peaks from different selected stations of three megacities (Islamabad, Abbottabad, and Haripur Hattar) in Pakistan were analyzed for paired comparisons. The tropospheric ozone levels were measured with the help of a portable SKY 2000-WH-O3 meter from December 2018 to November 2019. According to the findings of this investigation, the indoor ozone concentrations at Hattar Industrial Estate exceeded the permissible limit devised by the WHO. The highest concentration (0.37 ppm) was recorded in the month of May in the food industry, while the lowest concentration (0.00 ppm) was recorded in the cooling area of the steel industry in the month of December. For outdoor ozone concentrations, the maximum concentration (0.23 ppm) was detected in Islamabad in the month of March 2019, whereas the rest of year showed comparatively lower concentrations. In Haripur, the maximum concentration (0.22 ppm) was detected in the month of February 2019 and a minimum concentration (0.11 ppm) was found in the month of November 2019. In Abbottabad, the maximum concentration (0.21 ppm) was detected in the month of March 2019 and the minimum concentration was 0.082 ppm. Increasing tropospheric ozone levels might be harmful for local communities and industrial laborers in the winter season because of the foggy weather. In the Abbottabad and Hattar regions, since COVID infection is indirectly related to low temperature and high emission of gases may compromise the respiratory systems of humans. The results of the present study were shared with industrialists to set precautions for ambient air quality and support the adoption of low emission techniques in industries for the safety of labour and nearby residents.

COPD deaths attributable to ozone in 2019 and future projections using the WHO AQG 2021 in urban China

Chronic obstructive pulmonary disease (COPD) is an epidemic in China. Ozone is a possible risk factor of COPD, with ozone concentrations increasing in China, despite air pollution mitigation measures that reduced particulate matter. The WHO Air Quality Guidelines (AQG) recommendations in 2021 are a turning point that formally recognizes the crucial role of indoor air pollution. We aimed to investigate the premature COPD deaths attributable to ozone in 2019, taking the WHO AQG 2021 level into account to determine the gap to bridge ozone control in China. First, we assessed ozone exposures initiated from indoor and outdoor sources by gender and age groups in 344 cities under four scenarios: 2019 as a baseline, and outdoor ozone at WHO AQG 2021 level in 2019, 2030, and 2050, respectively. Subsequently, we estimated COPD deaths attributable to ozone. The results show that the COPD deaths attributable to ozone are 77,737 in 2019, and 527, 872, 1355 if the outdoor ozone concentration is reduced to the WHO AQG 2021 level in 2019 (counterfactual scenario), 2030, and 2050, respectively in urban China. The indoor ozone sources only contribute to less than 5% of COPD deaths. A gap of 68.5 μg/m3 for the highest seasonal ozone concentration should be bridged to meet the WHO AQG 2021 and avoid over 76 thousand (98%) COPD deaths in 2019 in urban China.

Impacts of building envelope design on indoor ozone exposures and health risks in urban environments

Much of human exposure to ozone takes place indoors. However, few studies have focused on human ozone exposures in normally occupied residential houses in the U.S. urban environments. Only rare studies have explored the implication of building envelope design variables on outdoor ozone penetration. Our study reveals the extent to which outdoor ozone penetrates and persists in the occupied houses in one of the most ozone-polluted cities, as influenced by building characteristics, building geometry, envelope design variables, window conditions and urban meteorology conditions. Through a set of analysis and variable regressions, we found that (1) the ratios of indoor to outdoor ozone concentration (I/O) were higher with windows open (0.700 ± 0.13) than with the windows closed (0.53 ± 0.22); (2) the indoor ozone concentration is typically elevated when the outdoor ozone concentration is high; and (3) design variables such as exterior envelope finishes, wall surface area and window-to-wall ratio are reasonably effective predictors. Our results of health risk evaluation suggest that the observed levels of indoor ozone exposure could pose a considerable risk to human health. Further work is needed to discover how building envelopes can be designed, constructed and maintained to support occupant health.

Ambient ozone effects on respiratory outcomes among smokers modified by neighborhood poverty: An analysis of SPIROMICS AIR

BackgroundNeighborhood poverty has been associated with poor health outcomes. Previous studies have also identified adverse respiratory effects of long-term ambient ozone. Factors associated with neighborhood poverty may accentuate the adverse impact of ozone on respiratory health. ObjectivesTo evaluate whether neighborhood poverty modifies the association between ambient ozone exposure and respiratory morbidity including symptoms, exacerbation risk, and radiologic parameters, among participants of the SPIROMICS AIR cohort study. MethodsSpatiotemporal models incorporating cohort-specific monitoring estimated 10-year average outdoor ozone concentrations at participants' homes. Adjusted regression models were used to determine the association of ozone exposure with respiratory outcomes, accounting for demographic factors, education, individual income, body mass index (BMI), and study site. Neighborhood poverty rate was defined by percentage of families living below federal poverty level per census tract. Interaction terms for neighborhood poverty rate with ozone were included in covariate-adjusted models to evaluate for effect modification. Results1874 participants were included in the analysis, with mean (± SD) age 64 (± 8.8) years and FEV1 (forced expiratory volume in one second) 74.7% (±25.8) predicted. Participants resided in neighborhoods with mean poverty rate of 9.9% (±10.3) of families below the federal poverty level and mean 10-year ambient ozone concentration of 24.7 (±5.2) ppb. There was an interaction between neighborhood poverty rate and ozone concentration for numerous respiratory outcomes, including COPD Assessment Test score, modified Medical Research Council Dyspnea Scale, six-minute walk test, and odds of COPD exacerbation in the year prior to enrollment, such that adverse effects of ozone were greater among participants in higher poverty neighborhoods. ConclusionIndividuals with COPD in high poverty neighborhoods have higher susceptibility to adverse respiratory effects of ambient ozone exposure, after adjusting for individual factors. These findings highlight the interaction between exposures associated with poverty and their effect on respiratory health.

Study on indoor ozone removal by PRM under the influence of typical factors

Ozone exposure has been proven to be strongly associated with both morbidity and mortality. In addition, the reaction of ozone with human skin sebum, building materials and indoor other compounds can cause secondary pollution of indoor environment. Therefore, how to effectively control indoor ozone pollution and its induced secondary pollution is an important scientific problem that needs to be solved in the field of indoor air quality. PRM (passive removal materials) can passively remove indoor ozone without energy consumption. According to the mechanism of ozone removal on PRM surface, the effects of material area, reaction probability, transport-limited deposition velocity, outdoor ozone concentration, air change rate (ACH) and indoor reaction rate on ozone removal rate of PRM were analyzed in this study. The results show that the ozone removal rate of PRM is greatly influenced by the reaction probability, the ACH, the surface area and the transport-limited deposition velocity, while the indoor reaction rate and outdoor ozone concentration have no obvious influence. Therefore, in order to remove more indoor ozone by PRM, the position and area of PRM with different reaction probabilities should be chosen reasonably.

Characteristics of indoor ozone pollution in residential buildings based on outdoor air pollution

Ozone pollution can not only cause serious effects on human respiratory tract, lung, cardiovascular and immune system, but also lead to secondary pollution of indoor air environment by reacting with human surface sebum, building materials surface and other indoor compounds. As people stay indoors for more than 90% of their time, indoor ozone exposure is far more harmful than outdoor ozone exposure. Indoor ozone mainly comes from the outdoor environment. Therefore, it is an important prerequisite for controlling indoor ozone pollution to master the characteristics of indoor ozone pollution concentration under the influence of outdoor air pollution. The outdoor ozone concentration of 20 representative cities in the five climatic areas of China were investigated in this study. Meanwhile, indoor ozone concentration was predicted based on I/O ratio (indoor-outdoor concentration ratio). Furthermore, the indoor ozone pollution level affected by window opening time, air change rate and ozone deposition velocity was analyzed. The results show that the increase of air change rate and window opening time leads to the rise of indoor ozone pollution level. Moreover, the growing up of ozone deposition velocity may cause more ozone to be removed by the indoor surface, then the indoor ozone concentration decreases. In addition, indoor ozone pollution is the most serious in cold zone and the least serious in mild zone.

A National Spatiotemporal Model for Ambient Ozone Concentration in the United States Using Universal Kriging and Land-use Regression: 2005-2014

Accurate prediction models for ambient air pollution concentrations are a key component of modern air pollution epidemiology, and epidemiological studies regarding long-term effects of ozone are urgently needed. Large-scale models are necessary for cohort studies with national recruitment, and models are also needed to accurately characterize fine-scale spatial gradients in a region. We applied a spatiotemporal modeling approach, previously used in individual cities for ozone and nationally for other pollutants, to predict weekly ambient ozone concentration over the contiguous United States for the period from 2005 through 2014. Methods: Using long-term regulatory ozone monitoring data collected daily (n=669 sites) and short-term spatially-rich cohort-specific data collected as two-week time integrated averages (n=1958 sites) divided into nine regions across the country, we fit a regionalized likelihood-based spatiotemporal model using land-use regression on dimension reduced land-use covariates combined with universal kriging. Ten-fold cross-validated predictions, leaving out sites, were used to compute R2 (from root mean-squared error) in three different ways: spatial R2 to assess accuracy in predicting long-term average exposures at locations without data, temporal R2 to assess accuracy in predicting the time series of weekly exposures at locations without data, and spatiotemporal R2 to assess overall prediction accuracy. Results: Overall cross-validated performance was high. Spatial R2 was 0.69, spatiotemporal R2 was 0.78, and median site-specific temporal R2 was 0.80. Spatial performance varied by modeling region and season. Conclusion: We report a novel, successful national-scale spatiotemporal model for outdoor ozone concentrations for the contiguous U.S. Strengths of this model include its national scale and its ability to make accurate fine-scale predictions spatially at all arbitrary points and temporally at one-week intervals, suggesting future usefulness to a wide variety of epidemiological studies.

Measurement of ozone deposition velocity onto human surfaces of Chinese residents and estimation of corresponding production of oxidation products

China has been experiencing a sharp increase in outdoor ozone concentration. The deposition velocity of ozone onto human surfaces strongly affects the indoor ozone concentration, and the production of oxidation products. In this study, we measured the deposition velocity of ozone onto human surfaces in six Chinese residential rooms, each housing 1–3 occupants. In addition, we estimated the corresponding emission rate of oxidation products. The measured mean value of the deposition velocity is 14.8 (±10.1) m/h, which is close to those reported in earlier studies in western countries. We also find that the ozone deposition velocity onto human surfaces is positively correlated to the weighted duration from the last laundry and bath/facial-cleansing, and it is negatively correlated to the relative humidity of the indoor air. The estimated emission rates of 6-MHO, 4-OPA, acetone, geranyl acetone, 1,4-butanedial decanal, and all gas-phase products are 7.7 × 1016, 6.7 × 1016, 9.4 × 1016, 9.7 × 1015, 1.3 × 1016, 3.4 × 1016, and 4.8 × 1017 molecule per person h−1, respectively, with an indoor ozone concentration of 5 ppb at steady state. The measured deposition velocity of ozone onto human surfaces of Chinese residents, and the emission rates of the corresponding oxidation products may be applied for the estimation of human exposure to ozone and its oxidation products in China.

Reviewing MnOx-based catalysts for decomposition of indoor ozone

Ozone is a highly reactive gas and one of important air pollutants for both indoor and outdoor environments. The Occupational Safety and Health Administration (OSHA) guideline for the ozone level limit at workplaces is 100 ppb for 8-hour exposure and the Health Canada guideline for the residential buildings is 20 ppb for 8 hour exposure. Therefore, applying an ozone removal technology in indoor environments is crucial when outdoor ozone concentration is high and/or where strong ozone emission sources exist. Activated carbon-based filters, thermal oxidation, catalytic oxidation, and photocatalytic oxidation are air treatment technologies that have been applied for ozone removal. Among these technologies, the catalytic oxidation approach showed better results, particularly manganese oxide (MnOx) based catalysts, which can decompose ozone to oxygen at room temperature. The low cost as well as high catalytic activity are among the advantages of MnOx-based catalysts. High specific surface area, high density of oxygen vacancy, high reducibility, low average oxidation state, and low relative humidity are beneficial for ozone decomposition over the catalyst. This review presents the importance of ozone removal from the indoor environments, its exposure issues, and the recent studies on MnOx-based catalyst for ozone decomposition.

Ozone in urban China: Impact on mortalities and approaches for establishing indoor guideline concentrations.

Reducing indoor ozone levels may be an effective strategy to reduce total exposure and associated mortality. Here we estimate (a) premature mortalities attributable to ozone for China's urban population ≥25years of age; (b) the fraction of total exposure occurring indoors; and (c) mortalities that can be potentially avoided through meeting current and more stringent indoor ozone standards/guidelines based on 1-hour daily maxima. To estimate ozone-attributable premature mortalities, we used hourly outdoor ozone concentrations measured at 1497 monitoring stations located in 339 Chinese cities and a published concentration-response model. We proceeded to estimate province-specific infiltration factors and co-occurring hourly indoor ozone concentrations. For the year 2015, we estimated that indoor exposures accounted for 59% (95% confidence interval (CI): 26%-79%) of the total ozone exposure that resulted in 70800 (95% CI: 35900-137700) premature all-cause mortalities in urban China. If the current Chinese indoor ozone standards (80ppbv (160µg/m3 ); 56ppbv (112µg/m3 )) were met, the mean estimates of reduction in mortalities would be indistinguishable from zero. With stricter 1-hour indoor ozone guidelines, the expected mortality reductions increase exponentially per unit decrease in indoor ozone. The analysis in this paper should help facilitate formulating present and future indoor ozone guidelines.

Preliminary assessment of outdoor and indoor air quality in Yangon city, Myanmar

Air pollution related problems in urban areas of developing countries get bigger quickly. Yangon is the most urbanized and most densely populated city in Myanmar. Information on air quality of Yangon is still lacking. Therefore, we conducted this study for initial assessment of outdoor and indoor air quality of Yangon. Four kinds of diffusive air samplers were used to measure volatile organic compounds (VOCs), ozone and carbonyl compounds, acidic gases and ammonia. As a result of this study, higher alkanes were found dominant among outdoor VOCs. Benzene/toluene ratios ranged from 0.15 to 0.53. Formaldehyde/acetaldehyde ratios varied from 1.5 to 2.4. Maximum outdoor ozone value was 26 μgm−3. A strong negative correlation between outdoor ozone and nitrogen dioxide concentrations was noted. Compared with previous local studies, outdoor nitrogen dioxide and sulfur dioxide concentrations were found to be on the increasing trend. The indoor/outdoor ratios at some sites revealed that there were indoor sources for α-pinene, d-limonene, p-dichlorobenzene and methyl isobutyl ketone. The ratios of pollutants with outdoor sources mostly ranged between 1 and 2. In conclusions, although it is a preliminary assessment, the findings can provide invaluable information towards comprehensive picture of air quality of Yangon. Outdoor air quality is found contaminated with pollutants most of which are traffic-related indicating that the city is now facing high traffic volume greater than before. Indoor air quality is varied with indoor characteristics of the buildings. Gases with health concern are identified in indoor air. Inadequate ventilation may precipitate poor indoor air quality.

Effects of tightening standards for indoor ozone levels on associated mortalities in urban China: a population-based modelling study

BackgroundPrevious studies have shown that exposure to ozone is associated with mortality. Reducing indoor ozone of outdoor origin may be an effective short-term method to reduce overall ozone exposure and the associated premature mortality. Here, we estimated (1) premature mortalities attributable to ozone for individuals aged 25 years and over in urban China, (2) the proportion of this mortality associated with time indoors, and (3) the mortality that might be achieved by meeting the current Chinese Indoor Air Quality Standard (IAQS) or Assessment Standard for Healthy Buildings (ASHB), as well as more stringent guidelines. MethodsOutdoor ozone concentrations were measured hourly at all 1497 government monitoring stations (as at 2015) located in 339 cities dispersed across China, and these data were used to estimate premature mortality in 2015 from circulatory and respiratory causes based on a concentration–response model derived from an extended analysis of the American Cancer Society Cancer Prevention Study II. We used estimated air exchange rates, ozone penetration factors, and ozone surface removal rates to estimate the corresponding indoor ozone concentrations for the hourly outdoor ozone measurements. Finally, we estimated mortality reductions that might be achieved in urban China by meeting different 1-h indoor ozone standards or guidelines. FindingsWe estimated that there were 61 000 premature deaths from respiratory and cardiovascular disease attributable to ozone among individuals aged 25 years or over in urban China in 2015. Indoor exposures accounted for 87% (53 000) of this total. If the current indoor ozone standards (IAQS 80 ppb; ASHB 56 ppb) were met, the reduction in total mortality would be indistinguishable from zero. To be meaningful, an indoor standard should be no higher than 30 ppb. InterpretationRegardless of whether a person is outdoors or indoors, the mortality risks associated with long-term ozone exposure are derived using data from outdoor ozone monitoring stations. Outdoor concentrations of ozone are substantially higher than the time-matched estimates of indoor ozone concentrations, reflecting the reactive chemistry of ozone indoors. Globally, guidelines for indoor ozone concentrations should be substantially lower than guidelines for outdoor ozone concentrations to account for both ozone and its indoor reaction products. FundingNatural Science Foundation of China (numbers 51420105010 and 51521005) and the National Key Research and Development Program of China (number 2017YFC0702700).

Outdoor and Indoor Ozone Concentration Estimation Based on Artificial Neural Network and Single Zone Mass Balance Model

Both outdoor and indoor ozone concentrations have negative health effects on human. This paper proposes an artificial neural network to estimate the outdoor ozone concentrations and a mass balance model tool to estimate indoor ozone concentrations. The prediction of outdoor and indoor ozone concentration levels is of great significance for people’s health. The estimation models are validated by the measured data selected from the monitoring stations and field measurements in a room in Nanjing, respectively. The accuracy of the estimation models is evaluated. The neural network built in this paper can generally estimate the outdoor ozone concentrations to some extent, while the single zone mass balance model is useful for predicting indoor ozone concentration levels.

Ozone, Electrostatic Precipitators, and Particle Number Concentrations: Correlations Observed in a Real Office during Working Hours

This study investigates the impacts of outdoor and indoor ozone concentrations, ESP operation and occupancy on particle number concentrations within a modern office in Changsha, China. The office's one-pass air handling system contains a mini-bag filter (MERV 12) followed by an electrostatic precipitator (ESP) and high efficiency particulate air (HEPA) filter. Over a five-week period the system was operated either without the ESP (Stage 1, first-third week) or with the ESP (Stage 2, fourth and fifth week). Ozone and particle number concentrations were measured on working days. During both stages, indoor ozone and particle number concentrations tracked the outdoor ozone concentration. When operating, the ESP produced approximately 29 mg h(-1) of ozone, increasing supply air ozone by 15 ppb and steady-state indoor ozone by about 3 ppb. Occupancy tended to decrease indoor ozone and increase particle levels. During occupancy, indoor particle levels were low (∼2600 particle/cm(3)) when the supply air ozone level was less than 18 ppb. Above this threshold, the supply air ozone concentration and indoor particle number concentration were linearly related, and ESP operation increased the average indoor particle level by about 22 000 particles/cm(3). The implications for worker exposure to both ozone and particles are discussed.

지상과 지하역사의 실내공기질 특성과 외기영향 평가

Abstract In this study, the air quality of underground and overground railway stations was evaluated focusing onthe degree of influence of the outside air quality. The measured components were particulate matter (PM 10 ), carbon dioxide (CO 2 ), carbon monoxide (CO), nitrogen dioxide (NO 2 ), formaldehyde (HCHO), ozone (O 3 ), total airborne bacteria (TAB), total volatile organic carbon (TVOC), and Radon (Rn), which are included in the maintenance standards and recommended standards of the Indoor Air Quality Management Act. Also, the indoor/outdoor concentration ratios of PM10, NO 2 , and O 3 were calculated to estimate the influence of the outdoor air quality. Theconcentrations of PM10 HCHO, TVOC, NO 2 , and Rn in the underground stations were found to be higher than thosein the overground stations. These results indicate that the (present) generation of contaminants are caused by the indoor source of the underground station. The ozone concentration of the overground stations was higher than thatof the underground stations, which indicates that the outdoor ozone concentration influenced that of the overgroundstations directly. Thus, methods of improving the IAQ should take into consideration the types of contamination

Particulate reactive oxygen species on total suspended particles - measurements in residences in Austin, Texas.

The biologically relevant characteristics of particulate matter (PM) in homes are important to assessing human health. The concentration of particulate reactive oxygen species (ROS) was assessed in eight homes and was found to be lower inside (mean±s.e.=1.59±0.33nmol/m3 ) than outside (2.35±0.57nmol/m3 ). Indoor particulate ROS concentrations were substantial and a major fraction of indoor particulate ROS existed on PM2.5 (58±10%), which is important from a health perspective as PM2.5 can carry ROS deep into the lungs. No obvious relationships were evident between selected building characteristics and indoor particulate ROS concentrations, but this observation would need to be verified by larger, controlled studies. Controlled experiments conducted at a test house suggest that indoor ozone and terpene concentrations substantially influence indoor particulate ROS concentrations when outdoor ozone concentrations are low, but have a weaker influence on indoor particulate ROS concentrations when outdoor ozone concentrations are high. The combination of substantial indoor concentrations and the time spent indoors suggest that further work is warranted to assess the key parameters that drive indoor particulate ROS concentrations.

Relations between isoprene and nitric oxide in exhaled breath and the potential influence of outdoor ozone: a pilot study

The role of endogenous isoprene in the human body, if any, is unclear because previous research is inconsistent and mechanistic evidence for the biologic function of isoprene is lacking. Given previous evidence that exhaled isoprene is elevated in systemic inflammatory states, we hypothesized that exhaled isoprene would be positively associated with a breath biomarker of airway inflammation, the fractional concentration of exhaled nitric oxide (FENO). We examined relationships of exhaled breath isoprene with FENO and with outdoor ozone given that ozone chemically reacts with isoprene and has been positively associated with FENO in past studies. Sixteen elderly subjects were followed with ≤12 weekly exhaled hydrocarbon and FENO collections at the subjects’ retirement community. Outdoor ozone concentrations were measured continuously on site. Mixed-effects regression analyses tested relations of FENO with isoprene, and FENO and isoprene with ozone, adjusted for temperature. We found FENO was inversely associated with isoprene, and this was not confounded by ozone. Isoprene was inversely related to ozone. FENO was positively related to ozone and this relation was not confounded by isoprene. In contrast to hypothesized relations, we conclude that exhaled isoprene is inversely associated with FENO as well as outdoor ozone, which suggests possible protective ozone-scavenging functions of endogenous isoprene. Findings may indicate chemical reactions of isoprene oxidation by ozone and by hydroxyl radicals in the presence of O2 that is dependent on NO concentration. These preliminary results need to be confirmed in additional studies of human subjects, particularly as they apply to FENO monitoring in asthma.

Effect of ventilation strategies on residential ozone levels

Elevated outdoor ozone levels are associated with adverse health effects. Because people spend the vast majority of their time indoors, reduction in indoor levels of ozone of outdoor origin would lower population exposures and might also lead to a reduction in ozone-associated adverse health effects. In most buildings, indoor ozone levels are diminished with respect to outdoor levels to an extent that depends on surface reactions and on the degree to which ozone penetrates the building envelope. Ozone enters buildings from outdoors together with the airflows that are driven by natural and mechanical means, including deliberate ventilation used to reduce concentrations of indoor-generated pollutants. When assessing the effect of deliberate ventilation on occupant health one should consider not only the positive effects on removing pollutants of indoor origin but also the possibility that enhanced ventilation might increase indoor levels of pollutants originating outdoors. This study considers how changes in residential ventilation that are designed to comply with ASHRAE Standard 62.2 might influence indoor levels of ozone. Simulation results show that the building envelope can contribute significantly to filtration of ozone. Consequently, the use of exhaust ventilation systems is predicted to produce lower indoor ozone concentrations than would occur with balanced ventilation systems operating at the same air-exchange rate. We also investigated a strategy for reducing exposure to ozone that would deliberately reduce ventilation rates during times of high outdoor ozone concentration while still meeting daily average ventilation requirements.

Long-term performance of passive materials for removal of ozone from indoor air

The health effects associated with exposure to ozone range from respiratory irritation to increased mortality. In this paper, we explore the use of three green building materials and an activated carbon (AC) mat that remove ozone from indoor air. We studied the effects of long-term exposure of these materials to real environments on ozone removal capability and pre- and post-ozonation emissions. A field study was completed over a 6-month period, and laboratory testing was intermittently conducted on material samples retrieved from the field. The results show sustained ozone removal for all materials except recycled carpet, with greatest ozone deposition velocity for AC mat (2.5-3.8 m/h) and perlite-based ceiling tile (2.2-3.2 m/h). Carbonyl emission rates were low for AC across all field sites. Painted gypsum wallboard and perlite-based ceiling tile had similar overall emission rates over the 6-month period, while carpet had large initial emission rates of undesirable by-products that decayed rapidly but remained high compared with other materials. This study confirms that AC mats and perlite-based ceiling tile are viable surfaces for inclusion in buildings to remove ozone without generating undesirable by-products. PRACTICAL IMPLICATIONS The use of passive removal materials for ozone control could decrease the need for, or even render unnecessary, active but energy consuming control solutions. In buildings where ozone should be controlled (high outdoor ozone concentrations, sensitive populations), materials specifically designed or selected for removing ozone could be implemented, as long as ozone removal is not associated with large emissions of harmful by-products. We find that activated carbon mats and perlite-based ceiling tiles can provide substantial, long-lasting, ozone control.