Search

In indoor environments, accretion of mass to materials may provide sites for surface chemistry that differ from those of the original material. Since indoor surfaces are a major sink of oxidant gases, surface mass accretion may impact indoor O 3 chemistry. In this study, the effect of surface mass accretion on O 3 surface deposition was tested by deploying cleaned borosilicate glass plates in two types of indoor environments: a mechanically ventilated (MV) office and a naturally ventilated (NV) residence located in Singapore. In each environment, seven replicate glass plates and one field blank were deployed for between 7 and 56 days and examined in a laboratory chamber for O 3 deposition rate and surface reaction probability. Average mass accretion to plates, deployed in a horizontal position and including deposited particles, was 10.6 mg/(m 2 d) in the MV office vs. 18.5 mg/(m 2 d) in the NV residence and the comparison is at the threshold of statistical significance ( p  = 0.054). Ozone reactivity to the plates increased in magnitude and persistence with longer plate deployment. Ozone reaction probabilities to cleaned plates prior to deployment ranged [0.06–0.74] × 10 −6 for two hours of observable removal whereas plates deployed for 56 days ranged [0.15–1.2] × 10 −6 for four hours of observable removal. Regressions of cumulative O 3 removed during chamber tests vs. mass accreted show removal of 4.3 nmol O 3 /mg for the NV residence and 2.4 nmol O 3 /mg for the MV office. These results imply that accretion of mass to surfaces may alter indoor O 3 transformation pathways. [ABSTRACT FROM AUTHOR]

It is well-established that indoor surfaces, such as building materials, act as a sink for indoor ozone. However, comparatively little research has been done regarding ozone reactions with human surfaces such as skin and clothing. Reaction characteristics of human surfaces and airflow around the human body may affect ozone removal and reaction byproduct formation. The objective of this study is to investigate effects of the reactivity of human surfaces, modeled for a range of reaction probabilities ( γ ), on ozone deposition and reaction byproduct formation. Computational fluid dynamics models are verified and validated with previously published studies, and used to analyze ozone reaction dynamics due to human surfaces under varying indoor air flow conditions. The results show that for indoor environments with air exchange rate <5 h −1 , ozone deposition velocity is in the range of 8–10 m/h for human skin oil while it is 2–3 m/h for clean clothing. Surface reactivity of the human body has a larger influence on the ozone deposition velocity than do the air exchange rates or indoor airflow patterns. Modeled emission rates of major reaction byproducts from ozone chemistry with human surfaces included acetone (0.3 mg/h/person), decanal (0.2 mg/h/person), nonanal (0.1 mg/h/person) and 6-MHO (0.1 mg/h/person) for a transport-limited scenario with 90 ppb bulk ozone concentration. These results imply that exposures to indoor ozone and reaction byproducts can be meaningfully modulated by an interaction of building airflow and chemistry occurring on and around individuals, and should be considered in models of human exposure. [ABSTRACT FROM AUTHOR]

Airborne particulate matter (PM) is closely linked to a range of adverse health outcomes such as oxidative stress-induced DNA damage and respiratory symptoms. A number of young children aged under 5 years spend a significant amount of time in nurseries worldwide. However, few studies examine children's exposure to PM in nursery environments. The objective of this study is to characterize five important metrics of particulate matter pollutants in urban nurseries in a mega-city, Seoul, Korea during winter days. 48 h field measurements were performed at four urban nurseries to monitor size-resolved particle number (PN) concentration (10–700 nm), lung-deposited surface area (LDSA, 10–1000 nm), and mass concentrations of PM 2.5 , PM 10 , and black carbon (BC). Other environmental parameters such as CO 2 concentration, temperature, and relative humidity (RH) were measured. Results show that indoor PN concentrations and LDSA are notably elevated during occupancy, mainly due to window opening. During window-open periods, the geometric mean of indoor particle size distribution is in the range of 30–40 nm, similar to the geometric mean of the outdoor particle size distribution. For all nurseries, the daily-integrated exposure to PN had an overall mean of 170 × 10 3 /cm 3 h/day and a relative standard deviation of 32%. The indoor mean concentrations of BC and LDSA during occupancy is comparable to those of busy roads in populated cities such as Zurich, Lisbon and Barcelona, suggesting high potential for lung deposition of UFP in nursery classrooms. [ABSTRACT FROM AUTHOR]

Indoor carbon dioxide (CO 2 ) levels serve as an indicator of ventilation sufficiency in relation to metabolic effluents. Recent evidence suggests that elevated CO 2 exposure (with or without other bioeffluents) may cause adverse cognitive effects. In shelter-in-place (SIP) facilities, indoor CO 2 levels may become particularly elevated. This study evaluates four low-cost alkaline earth metal oxides and hydroxides as CO 2 sorbents for potential use in indoor air cleaning applications. Sorbents studied were MgO, Mg(OH) 2 , Ca(OH) 2 and commercially available soda lime. Uncarbonated sorbents characterized with nitrogen adsorption porosimetry showed BET surface areas in the 5.6–27 m 2 /g range. Microstructural analyses, including X-ray diffraction, thermogravimetric analysis and scanning electron microscopy confirmed the carbonation mechanisms and extent of sorption under environmental conditions typical of indoor spaces. Ca-based sorbents demonstrated higher extent of carbonation than Mg-based sorbents. Laboratory parameterizations, including rate constants ( k ) and carbonation yields ( y ), were applied in material balance models to assess the CO 2 removal potential of Ca-based sorbents in three types of indoor environments. Soda lime ( k = [2.2–3.6] × 10 −3 m 3 mol CO 2 −1 h −1 , y = 0.49–0.51) showed potential for effective use in SIP facilities. For example, CO 2 exposure in a modeled SIP facility could be reduced by 80% for an 8-h sheltering interval and to levels below 5000 ppm for an 8-h period with a practically sized air cleaner. Predicted effectiveness was more modest for bedrooms and classrooms. [ABSTRACT FROM AUTHOR]

Elevated indoor CO 2 levels are indicative of insufficient ventilation in occupied spaces and correlate with elevated concentrations of pollutants of indoor origin. Adverse health and well-being outcomes associated with elevated indoor CO 2 levels are based on CO 2 as a proxy, although some emerging evidence suggests CO 2 itself may impact human cognition. Using portable monitors, we conducted an exposure study with 16 subjects in Singapore to understand the levels, dynamics and influencing factors of personal exposure to CO 2 . Participants carried a CO 2 monitor continuously for 7-day periods recording their exposure levels at 1-min intervals. A recall diary was maintained of time-microenvironment-activity budget. We found that the mode of bedroom ventilation was a major determinant of CO 2 exposure. Approximately half of the participants slept in bedrooms employing ductless split air-conditioners (group “AC”); half slept in bedrooms naturally ventilated through operable windows (group “NV”). Median CO 2 exposure levels for AC vs. NV groups are significantly different ( x ˜ A C = 650 ppm vs. x ˜ N V = 550 ppm, p < 0.001). Mean daily integrated exposures for group AC were statistically higher than for group NV: 22,800 ppm h/d vs. 16,000 ppm h/d ( p < 0.005). Exposure events associated with potential adverse cognitive implications (duration > 2.5 h, average CO 2 mixing ratio > 1000 ppm) occurred, on average, at frequencies of 0.5 d −1 across all participants, 0.6 d −1 for AC participants and 0.2 d −1 for NV participants. The majority of such events occurred in the home (86%), followed by work (9%) and transit (3%). [ABSTRACT FROM AUTHOR]

Much of human exposure to ambient ozone and ozone reaction byproducts occurs inside buildings. However, there are currently no experimental data on the ability of ozone to penetrate through building envelopes and into residences. This paper presents a method to determine the penetration factor for ozone in buildings, and applies it in an unoccupied test house and seven single-family residences. The mean (±SD) ozone penetration factor was measured as 0.79 ± 0.13 in the eight homes using this method, ranging from 0.62 ± 0.09 to 1.02 ± 0.15. An analysis of tests across the homes revealed that ozone penetration was significantly higher in homes with more painted wood envelope materials, homes with larger air leakage exponents from fan pressurization tests, and older homes. The test method utilizes a large calibrated fan to elevate air exchange rates and steady-state indoor ozone concentrations to levels that can be accurately measured, so there is a potential for overpredicting ozone penetration factors. However, evidence suggests that this bias is likely small in most of the homes, and, even if a bias exists, the measured ozone penetration factors were lower than the usual assumption of unity in seven of the eight tested homes. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a Monte Carlo simulation to assess passive removal materials (PRMs) that remove ozone with no additional energy input and minimal byproduct formation. Distributions for air exchange rate in a subset of homes in Houston, Texas, were taken from the literature and combined with background ozone removal rates in typical houses and previous experimentally determined ozone deposition velocities to activated carbon cloth and gypsum wallboard PRMs. The median ratio of indoor to outdoor ozone was predicted to be 0.16 for homes with no PRMs installed and ranged from 0.047 to 0.12 for homes with PRMs. Median values of ozone removal effectiveness in these homes ranged from 22% to 68% for the conditions investigated. Achieving an ozone removal effectiveness above 50% in half of the homes would require installing a large area of PRMs and providing enhanced air speed to transport pollutants to PRM surfaces. Challenges associated with achieving this removal include optimizing indoor transport and aesthetic implications of large surface areas of PRM materials. [Copyright &y& Elsevier]

We conducted a series of experiments to evaluate the gas and particle removal effectiveness and potential for byproduct formation resulting from the operation of a commercially available in-duct bipolar ionization device. Laboratory tests were conducted with the ionizer installed in a small air handler serving a large semi-furnished chamber. Chamber experiments were conducted under (i) normal operating conditions to characterize the impact of the ionizer on concentrations of particles (0.01–10 μm), ozone (O 3), nitrogen dioxide (NO 2), volatile organic compounds (VOCs), and aldehydes, and (ii) particle injection and decay conditions to characterize the impact of the ionizer operation on particle loss rates. The field test involved air sampling of particulates (0.01–10 μm), O 3 , and VOCs upstream and downstream of an operating ionizer device installed in an air handling unit serving an occupied office building. Both the chamber and field tests suggested that the use of the tested bipolar ionization unit led to a decrease in some hydrocarbons (e.g., xylenes) among the lists of compounds we were able to analyze, but an increase in others, most prominently oxygenated VOCs (e.g., acetone, ethanol) and toluene. Ionizer operation appeared to minimally impact particle, O 3 , and NO 2 concentrations during normal operating conditions. Particle injection and decay experiments in the chamber suggest that operation of the ionizer unit led to a small increase in loss rates for ultrafine particles (<0.15 μm) and a small decrease in loss rates for larger particles (>0.3 μm), but with negligible net changes in estimated PM 2.5 loss rates. • Laboratory and field tests conducted to characterize bipolar ionization device. • Evaluated impacts on gas and particle removal and byproduct formation. • Ionization decreased some hydrocarbons but increased others. • Ionization minimally impacted particles, ozone, and nitrogen dioxide. • Ionization shifted particle size distribution but did not impact PM 2.5 mass. [ABSTRACT FROM AUTHOR]

A broad range of building performance monitoring, sampling, and evaluation was conducted periodically after construction and spanning more than a year, for an occupied office building constructed using mass timber elements such as cross-laminated timber (CLT) floor and roof panels, as well as glue-laminated timber (GLT) beams and columns. This case study contributes research on monitoring indoor environmental quality in buildings, describing one of the few studies of an occupied mass timber building, and analyzing data in three areas that impact occupant experience: indoor air quality, bacterial community composition, and floor vibration. As a whole, the building was found to perform well. Volatile organic compounds (VOCs), including formaldehyde, were analyzed using multiple methods. Formaldehyde was found to be present in the building, though levels were below most recommended exposure limits. The source of formaldehyde was not able to be identified in this study. The richness of the bacterial community was affected by the height of sampling with respect to the floor, and richness and composition was affected by the location within the building. Floor vibration was observed to be below recognized human comfort thresholds. [ABSTRACT FROM AUTHOR]

The authors discuss the progress and priorities in the reduction of indoor air pollution (IAP) in developing countries. They mention a symposium on IAP in developing countries at the Indoor Air 2011 conference which was held at the University of Texas at Austin from June 6 to 7, 2011. They note that supervisors need to encourage and support their graduate students to conduct research which is relevant to public health issues.

Indoor air quality is affected by indoor materials such as carpets that may act as sources and/or sinks of gas-phase air pollutants. Heterogeneous reactions of ozone with carpets may result in potentially harmful products. In this study, indoor residential carpets of varying fiber types were tested to evaluate their ability to remove ozone, and to assess their role in the production of carbonyls when exposed to elevated levels of ozone. Tests were conducted with six types of new unused carpets. Two sets of experiments were conducted, the first measured ozone removal and ozone deposition velocities, and the second measured primary carbonyl production and secondary production as a result of exposure to ozone. The tests were conducted using glass chambers with volume of 52 L each. Air exchange rates for all tests were 3 h −1 . The ozone removal tests show that, for the conditions tested, the polyester carpet sample had the lowest ozone removal (40%), while wool carpet had the greatest ozone removal (65%). Most carpet samples showed higher secondary than primary carbonyl emissions, with carpets containing polypropylene fibers being a notable exception. Carpets with polyester fibers had both the highest primary and secondary emissions of formaldehyde among all samples tested. While it is difficult to make blanket conclusions about the relative air quality merits of various carpet fiber options, it is clear that ozone removal percentages and emissions of volatile organic compounds can vary drastically as a function of fiber type. [ABSTRACT FROM AUTHOR]