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The chemical composition studies of indoor particulate matter (PM2.5 and PM0.1) are lacking in the developing world, yet the attention to indoor air pollution and occupant health risks is rising. This study therefore aims to investigate the chemical compositions of indoor and outdoor PM2.5 and PM0.1 in residential and school buildings in Vietnam during different seasons and the effects of emission sources on particle characteristics. The results show that the concentration of indoor PM2.5 in the residential house was higher than that outdoors, and the indoor-to-outdoor ratios (I/O) exceeded 1, indicating the contribution of indoor sources. The peak concentration of indoor particles was observed during the incense burning days, whereas a higher indoor organic carbon concentration may be due to cooking activities. A similar variation of indoor and outdoor PM2.5 indicates the penetration of outdoor particles. In the school building, seasonal variations in indoor PM0.1 and its chemical species were observed, suggesting outdoor sources had a significant effect. Several factors may affect I/O and the infiltration factor of PM0.1, such as indoor sources, air exchange rate, cracks in the door and window, and particle deposition rate. The reason for the I/O value slightly above 1 for PM0.1 in this study remained unclear. Further investigations are recommended to obtain knowledge regarding the penetration of particles, particularly PM0.1. The findings provide a better understanding of the chemical components of indoor particles and the effects of emission sources, which is crucial to developing management measures for indoor air quality and mitigating exposures. [ABSTRACT FROM AUTHOR]

Airborne transmission has been confirmed as one of three principal ways of SARS-CoV-2 transmission. To reduce the transmission of SARS-CoV-2 indoors, understanding the distribution of respiratory droplets (or aerosols) present in human breath seems therefore important. To study whether the CO2 concentration can be used as a proxy for the number of exhaled particles present in an occupied space, the distribution of particles with different diameters (0.3, 0.5, 1.0, 2.5, 5.0 and 10 μm) and CO2 concentrations were monitored in a classroom setting with six healthy subjects. Additionally, numbers of particles with the same sizes were measured in the breath of the same six healthy subjects separately. Results showed that (1) on the contrary to CO2, the main source of indoor particles came from outdoor air, and not from occupants; (2) the impacts of ventilation regimes on indoor particle numbers were different to the impacts on CO2 concentrations; and (3) almost no significant relationship between the number of indoor particles and CO2 concentration was observed. Based on these results, this study could therefore not conclude that the CO2 concentration in a classroom can be used as a proxy for the number of exhaled particles by the occupants. [ABSTRACT FROM AUTHOR]

This study presents indoor and outdoor levels of airborne fine particles (PM2.5), particle bound polycyclic aromatic compounds (PACs) including parent-, alkylated-, nitro-, and oxy-PAHs. Week-long simultaneous measurements were conducted inside and outside 15 occupied homes in southern Sweden during wintertime. The homes were single-family houses or apartments located in urban, semi-urban, and rural areas. The PM2.5 and PACs levels were low compared to studies worldwide. There was great variation in concentrations between sites, which likely is due to proximity to road and traffic intensity. The lower concentrations of nitro and oxy-PAHs compared to parent PAHs in this study, compared to other studies, could possibly be due to lower atmospheric photochemical formation outdoors because the cold climate. This assumption could not be confirmed and need to be further tested. The results point to that particle PAC levels found inside arise primarily from outdoor. This correlation was not as clear for PM2.5. The results of a comparison between residences before and after energy renovation did not indicate an improvement in indoor air regarding PACs. To understand exposure and assess risks it is important to measure wide range of PACs both in gas and particle phase. [ABSTRACT FROM AUTHOR]

Printers can release numerous particles to contaminate indoor environments and pose health risks. Clarifying the exposure level and physicochemical properties of printer-emitted particles (PEPs) will help to evaluate the health risks of printer operator. In our study, the particles concentration in the printing shop was monitored in real time for a long time (12 h/day, total 6 days), and the PEPs were collected to characterize their physicochemical properties including shape, size and compositions. The result showed that the concentration of PEPs is closely related to the printing workload and the highest particle mass concentration of PM10 and PM2.5 was 212.73 μg m−3 and 91.48 μg m−3, respectively. The concentration of PM1 in the printing shop was in the range of 11.88–80.59 μg m−3 for mass value, and 174.83–1348.84 P cm−3 for count value which changed with the printing volume. The particle sizes of PEPs were less than 900 nm, 47.99% of PEPs was less than 200 nm, and 14.21% of the particles were at the nanoscale. PEPs contained 68.92% organic carbon (OC), 5.31% elemental carbon (EC), 3.17% metal elements, and 22.60% other inorganic additives, which contained more OC and metal elements than toners. Total polycyclic aromatic hydrocarbons (PAHs) levels were 18.95 ng/mg in toner and 120.70 ng/mg in PEPs. The carcinogenic risk of PAHs in PEPs was 1.40 × 10–7. These findings suggested future studies should pay more attention to the health effects of printing workers exposed to nanoparticles. [ABSTRACT FROM AUTHOR]

Low-cost monitors make it possible now for the first time to collect long-term (months to years) measurements of potential indoor exposure to fine particles. Indoor exposure is due to two sources: particles infiltrating from outdoors and those generated by indoor activities. Calculating the relative contribution of each source requires identifying an infiltration factor. We develop a method of identifying periods when the infiltration factor is not constant and searching for periods when it is relatively constant. From an initial regression of indoor on outdoor particle concentrations, a Forbidden Zone can be defined with an upper boundary below which no observations should appear. If many observations appear in the Forbidden Zone, they falsify the assumption of a single constant infiltration factor. This is a useful quality assurance feature, since investigators may then search for subsets of the data in which few observations appear in the Forbidden Zone. The usefulness of this approach is illustrated using examples drawn from the PurpleAir network of optical particle monitors. An improved algorithm is applied with reduced bias, improved precision, and a lower limit of detection than either of the two proprietary algorithms offered by the manufacturer of the sensors used in PurpleAir monitors. [ABSTRACT FROM AUTHOR]

This paper reports on the design, and implementation of piezoelectric-on-silicon MEMS resonators installed within a portable experimental setup for sensing nanoparticles in a laboratory environment. MEMS oscillators with a center frequency of approximately 5.999 MHz are employed for sensing 50 nm size-selected silver nanoparticles generated in the laboratory. The same experimental setup is then assembled to sense indoor particles that are present in the laboratory environment. The challenges associated with particle deposition as a result of assembling the portable experimental setup is highlighted. Furthermore, the MEMS oscillators demonstrate that the total mass of silver nanoparticles deposited onto the MEMS resonator surface using the inertial impaction technique-based experimental setup is approximately 7.993 nanograms. The total indoor particle mass accumulated on the MEMS resonator surface is estimated to be approximately 1.732 nanograms and 26.9 picograms for two different runs. The frequency resolution of the MEMS oscillator is estimated to be approximately 32 ppb and, consequently, the minimum detectable particle mass is approximately 60 femtograms for a 9.2 s integration time. [ABSTRACT FROM AUTHOR]

Elevated exposure to airborne particulate matter is linked to deleterious health and well-being outcomes. Exposure assessment can be improved through enhanced understanding of source-receptor relationships, for example as expressed in the inhalation intake fraction metric. This study provides new knowledge about how inhalation intake of airborne particles varies with spatially varying indoor emissions. In a controlled environmental chamber with low background particle levels, we monitored the time- and size-resolved particle concentrations at multiple locations including the subject's breathing zone. We investigated two types of particle emissions: (i) controlled releases from several specific indoor locations; and (ii) natural release from skin and clothing for a range of simulated occupant activities. Findings show that particles released proximate to the human envelope caused a total inhalation intake fraction of 7–10 per thousand, which was 1.5–16 × higher than the intake fraction for other indoor release locations. These outcomes reflect the influence of emissions-receptor proximity combined with the efficient transport of particles by means of the thermal plume to the breathing zone. The results show that the well-mixed representation of an indoor environment could underestimate the inhalation intake by 40–90% for various localized indoor emissions, and by up to 3 × for particles emitted from the human envelope. The post-release exposure period contributed substantially to total inhalation intake. For particles released naturally from the human envelope, inhalation intake fractions varied with activity type and were higher for a subject when seated rather than walking.

Elevated exposure to airborne particulate matter is linked to deleterious health and well-being outcomes. Exposure assessment can be improved through enhanced understanding of source-receptor relationships, for example as expressed in the inhalation intake fraction metric. This study provides new knowledge about how inhalation intake of airborne particles varies with spatially varying indoor emissions. In a controlled environmental chamber with low background particle levels, we monitored the time- and size-resolved particle concentrations at multiple locations including the subject's breathing zone. We investigated two types of particle emissions: (i) controlled releases from several specific indoor locations; and (ii) natural release from skin and clothing for a range of simulated occupant activities. Findings show that particles released proximate to the human envelope caused a total inhalation intake fraction of 7–10 per thousand, which was 1.5–16 × higher than the intake fraction for other indoor release locations. These outcomes reflect the influence of emissions-receptor proximity combined with the efficient transport of particles by means of the thermal plume to the breathing zone. The results show that the well-mixed representation of an indoor environment could underestimate the inhalation intake by 40–90% for various localized indoor emissions, and by up to 3 × for particles emitted from the human envelope. The post-release exposure period contributed substantially to total inhalation intake. For particles released naturally from the human envelope, inhalation intake fractions varied with activity type and were higher for a subject when seated rather than walking.

Mechanical and natural ventilations are effective measures to remove indoor airborne contaminants, thereby creating improved indoor air quality (IAQ). Among various simulation techniques, Markov chain model is a relatively new and efficient method in predicting indoor airborne pollutants. The existing Markov chain model (for indoor airborne pollutants) is basically assumed as first-order, which however is difficult to deal with airborne particles with non-negligible inertial. In this study, a novel weight-factor-based high-order (second-order and third-order) Markov chain model is developed to simulate particle dispersion and deposition indoors under fixed and dynamic ventilation modes. Flow fields under various ventilation modes are solved by computational fluid dynamics (CFD) tools in advance, and then the basic first-order Markov chain model is implemented and validated by both simulation results and experimental data from literature. Furthermore, different groups of weight factors are tested to estimate appropriate weight factors for both second-order and third-order Markov chain models. Finally, the calculation process is properly designed and controlled, so that the proposed high-order (second-order) Markov chain model can be used to perform particle-phase simulation under consecutively changed ventilation modes. Results indicate that the proposed second-order model does well in predicting particle dispersion and deposition under fixed ventilation mode as well as consecutively changed ventilation modes. Compared with traditional first-order Markov chain model, the proposed high-order model performs with more reasonable accuracy but without significant computing cost increment. The most suitable weight factors of the simulation case in this study are found to be (λ1 = 0.7, λ2 = 0.3, λ3 = 0) for second-order Markov chain model, and (λ1 = 0.8, λ2 = 0.1, λ3 = 0.1) for third-order Markov chain model in terms of reducing errors in particle deposition and escape prediction. With the improvements of the efficiency of state transfer matrix construction and flow field data acquisition/processing, the proposed high-order Markov chain model is expected to provide an alternative choice for fast prediction of indoor airborne particulate (as well as gaseous) pollutants under transient flows. [ABSTRACT FROM AUTHOR]

Indoor environment is the place where people spend most of their time throughout their whole life. Accordingly, the assessment of exposure to particulate matter (PM) in indoor environment is crucial in order to determine the possible health effects. In this study, the number concentration of PM range from 10 nm to 10 µm in size, deposition of PM in the respiratory tract, and the inhalation dose for the residents (dormitory, library, canteen, dining-hall, activity center, mosque, gymnasium, hospital, and classroom) were investigated. An optical particle sizer and a NanoScan scanning mobility particle sizer were used to measure the particle number concentrations in the size range of 10 nm to 300 nm and 300 nm to 10 µm, respectively. The total number concentrations varied from 1.32 × 105 cm−3 to 1.11 × 103 cm−3. Deposition of particles in the respiratory system was predicted by the ICRP model. It was found that 48% of inhaled particles of 20 nm in size was the deposition in the alveolar region whereas 9.6% and 16% were in the head airway and tracheobronchial region, respectively. Maximum inhalation doses were obtained for ultrafine particles in all microenvironments. Finally, the mass deposition in the gymnasium was the highest although the particle concentration was at the last four among other microenvironments. That means physical exertion is a significant factor besides the particle concentration. [ABSTRACT FROM AUTHOR]

Low-cost monitors make it possible now for the first time to collect long-term (months to years) measurements of potential indoor exposure to fine particles. Indoor exposure is due to two sources: particles infiltrating from outdoors and those generated by indoor activities. Calculating the relative contribution of each source requires identifying an infiltration factor. We develop a method of identifying periods when the infiltration factor is not constant and searching for periods when it is relatively constant. From an initial regression of indoor on outdoor particle concentrations, a Forbidden Zone can be defined with an upper boundary below which no observations should appear. If many observations appear in the Forbidden Zone, they falsify the assumption of a single constant infiltration factor. This is a useful quality assurance feature, since investigators may then search for subsets of the data in which few observations appear in the Forbidden Zone. The usefulness of this approach is illustrated using examples drawn from the PurpleAir network of optical particle monitors. An improved algorithm is applied with reduced bias, improved precision, and a lower limit of detection than either of the two proprietary algorithms offered by the manufacturer of the sensors used in PurpleAir monitors.

Airborne particle transport in indoor environments plays an important role in occupant exposure to aerosols and public health problems. Several studies have examined indoor airflow and particle transport using computational fluid dynamics models. For the Lagrangian particle tracking model, the minimum particle concentration necessary for accurate prediction may vary with the airflow regime and sampling volume. Nonetheless, only a few studies have systematically quantified suitable particle numbers and sampling volumes, according to indoor airflow and ventilation conditions. This study addresses this gap by exploring quality control strategies for a Lagrangian particle tracking model to reliably predict indoor particle transport. Based on transient simulations, we analyzed the spatiotemporal distributions of indoor particle trajectories while varying the number of particles, sampling volume, and ventilation strategy. The results indicate that in general a sampling volume of 5 L can predict the normalized mean concentrations better than a 1 L sampling volume, particularly when dealing with a smaller number of particles. Furthermore, the required particle number concentrations vary significantly depending on the chosen ventilation strategy. For instance, under the conditions of a 5 L sampling volume and an air exchange rate of 2.7 h−1, the minimum particle number concentrations for achieving reliable modeling predictions were observed to be 0.0075 cm−3 for displacement ventilation and 0.015 cm−3 for mixing ventilation. These results highlight the crucial role of the number of simulated particle trajectories in Lagrangian particle tracking models in determining prediction quality. The study findings suggest that quality control measures should acknowledge the significant variability in required particle numbers, which can often differ by an order of magnitude, contingent upon the specific combination of ventilation strategy and sampling volume. • Quality control strategies for Lagrangian simulation were evaluated. • At a ventilation rate of 2.7 h−1, minimum concentration ranged 0.0075–0.015 cm−3. • A 5 L sampling volume improves prediction reliability compared to 0.5 L and 1 L. • Minimum particle concentrations varied with ventilation strategy over 10 times. [ABSTRACT FROM AUTHOR]

The intensity, frequency, duration, and contribution of distinct PM2.5 sources in Asian households have seldom been assessed; these are evaluated in this work with concurrent personal, indoor, and outdoor PM2.5 and PM1 monitoring using novel low‐cost sensing (LCS) devices, AS‐LUNG. GRIMM‐comparable observations were acquired by the corrected AS‐LUNG readings, with R2 up to 0.998. Twenty‐six non‐smoking healthy adults were recruited in Taiwan in 2018 for 7‐day personal, home indoor, and home outdoor PM monitoring. The results showed 5‐min PM2.5 and PM1 exposures of 11.2 ± 10.9 and 10.5 ± 9.8 µg/m3, respectively. Cooking occurred most frequently; cooking with and without solid fuel contributed to high PM2.5 increments of 76.5 and 183.8 µg/m3 (1 min), respectively. Incense burning had the highest mean PM2.5 indoor/outdoor (1.44 ± 1.44) ratios at home and on average the highest 5‐min PM2.5 increments (15.0 µg/m3) to indoor levels, among all single sources. Certain events accounted for 14.0%‐39.6% of subjects' daily exposures. With the high resolution of AS‐LUNG data and detailed time‐activity diaries, the impacts of sources and ventilations were assessed in detail. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the impact of ventilation and filtration conditions on particle concentrations in an orthopedic operating room. Total particle, viable particle, and CO2 concentration were measured under three different situations, namely before air filter replacement, after air filter replacement, and in an operating room with a new air conditioning system. Before air filter replacement, the mean values of airflow, total particle concentration, and viable particle concentration were 706 m3/h, 15.0 × 106 ± 4.0 × 106 particles/m3, and 57 CFU/m3, respectively. After replacement, the airflow increased to 1954 m3/h, and total and viable particle concentrations decreased to 0.4 × 106 ± 0.2 × 106 particles/m3 and 24 CFU/m3, respectively. In the room with a new air conditioning system, the airflow was 2051 m3/h, and total and viable particle concentrations were 0.3 × 106. ± 0.1 × 106 particles/m3 and 15 CFU/m3, respectively. The CO2 levels were 663 ppm (before), 659 ppm (after), and 574 ppm (new room). The results showed that inappropriate or no maintenance of filters in an air conditioning system had significant negative effects on indoor air quality in operating rooms. Air conditioning systems operating with saturated filters can be affected by pressure drop, which can lead to a reduction in airflow, thereby resulting in an increase in the average total particle and viable particle concentrations and the risk of infection in operating rooms. However, the results showed that the CO2 concentration was not affected by the filter replacement. Article Highlights: Improper maintenance of the air filters poses negative effects in operating rooms. Particles remain inside the room with less air exchange caused by saturated filters. Change in filters produces a greater effect on air quality in operating rooms. CO2 concentration generated by the people may not be affected by the filter replacement. [ABSTRACT FROM AUTHOR]

Ozone reaction with human surfaces is an important source of ultrafine particles indoors. However, 1-20 nm particles generated from ozone-human chemistry, which mark the first step of particle formation and growth, remain understudied. Ventilation and indoor air movement could have important implications for these processes. Therefore, in a controlled-climate chamber, we measured ultrafine particles initiated from ozone-human chemistry and their dependence on the air change rate (ACR, 0.5, 1.5, and 3 h -1 ) and operation of mixing fans (on and off). Concurrently, we measured volatile organic compounds (VOCs) and explored the correlation between particles and gas-phase products. At 25-30 ppb ozone levels, humans generated 0.2-7.7 × 10 12 of 1-3 nm, 0-7.2 × 10 12 of 3-10 nm, and 0-1.3 × 10 12 of 10-20 nm particles per person per hour depending on the ACR and mixing fan operation. Size-dependent particle growth and formation rates increased with higher ACR. The operation of mixing fans suppressed the particle formation and growth, owing to enhanced surface deposition of the newly formed particles and their precursors. Correlation analyses revealed complex interactions between the particles and VOCs initiated by ozone-human chemistry. The results imply that ventilation and indoor air movement may have a more significant influence on particle dynamics and fate relative to indoor chemistry.

Organic aerosol (OA) is chemically dynamic, continuously evolving by oxidative chemistry, for instance, via hydroxyl radical (OH) reactions. Studies have explored this evolution (so‐called OA aging) in the atmosphere, but none have investigated it indoors. Aging organic molecules in both particle and gas‐phases undergo changes in oxygen content and volatility, which may ultimately either enhance or reduce the condensed‐phase OA concentration (COA). This work models OH‐induced aging using the two‐dimensional volatility basis set (2D‐VBS) within an indoor model and explores its significance on COA relative to prior modeling methodologies which neglect aging transformations. Lagrangian, time‐averaged, and transient indoor simulations were conducted. The time‐averaged simulations included a Monte Carlo procedure and sensitivity analysis, using input distributions typical of U.S. residences. Results demonstrate that indoors, aging generally leads to COA augmentation. The extent to which this is significant is conditional upon several factors, most notably temperature, OH exposure, and OA mass loading. Time‐averaged COA was affected minimally in typical residences (<5% increase). However, some plausible cases may cause stronger COA enhancements, such as in a sunlit room where photolysis facilitates significant OH production (~20% increase), or during a transient OH‐producing cleaning event (~35% peak increase). [ABSTRACT FROM AUTHOR]

Abstract People generally spend more time indoors than outdoors resulting in a higher proportion of exposure to particulate matter (PM) occurring indoors. Consequently, indoor PM levels, in contrast to outdoor PM levels, may have a stronger relationship with lung function. To test this hypothesis, indoor and outdoor PM 2.5 and fungal spore data were simultaneously collected from the homes of forty-four asthmatic children aged 10–16 years. An optical absorption technique was utilized on the collected PM 2.5 mass to obtain concentrations of black carbon (BC) and ultraviolet light absorbing particulate matter, (UVPM; a marker of light absorbing PM 2.5 emitted from smoldering organics). Enrolled children completed spirometry after environmental measurements were made. Given the high correlation between PM 2.5 , BC, and UVPM, principal component analysis was used to obtain uncorrelated summaries of the measured PM. Separate linear mixed-effect models were developed to estimate the association between principal components of the PM variables and spirometry values, as well as the uncorrelated original PM variables and spirometry values. A one-unit increase in the first principal component variable representing indoor PM (predominantly composed of UVPM and PM 2.5) was associated with 4.1% decrease (99% CI = −6.9, −1.4) in FEV 1 /FVC ratio. 11.3 μg/m3 increase in indoor UVPM was associated with 6.4% and 14.7% decrease (99% CI = −10.4, −2.4 and 99% CI = −26.3, −2.9, respectively) in percent predicted FEV 1 /FVC ratio and FEF 25–75 respectively. Additionally, 17.7 μg/m3 increase in indoor PM 2.5 was associated with 6.1% and 12.9% decrease (99% CI = −10.2, −1.9 and 99% CI = −24.9, −1.0, respectively) in percent predicted FEV 1 /FVC ratio and FEF 25–75 , respectively. Outdoor PM, indoor BC, and indoor fungal spores were not significantly associated with lung function. The results indicate that indoor PM is more strongly associated with lung function in children with asthma as compared with outdoor PM. Graphical abstract Unlabelled Image Highlights • Reduced lung function (FEV 1 /FVC ratio and FEF 25–75) is more strongly associated with indoor particles than outdoor particles. • Lung function is more strongly associated with UVPM than PM 2.5 or black carbon. • Low levels of black carbon indoors (0.6 μg/m3) may not be associated with lung function. [ABSTRACT FROM AUTHOR]

Cooking activities emit myriad low-volatility, semivolatile, and highly volatile organic compounds that together form particles that can accumulate to large indoor concentrations. Absorptive partitioning thermodynamics governs the particle-phase organic aerosol concentration mainly via temperature and sorbing mass impacts. Cooking activities can increase the organic sorbing mass by 1-2 orders of magnitude, increasing particle-phase concentrations and affecting emission rate calculations. Although recent studies have begun to probe the volatility characteristics of indoor cooking particles, parametrizations of cooking particle mass emissions have largely neglected these thermodynamic considerations. Here, we present an improved thermodynamics-based model framework for estimating condensable organic material emission rates from a time series of observed concentrations, given that adequate measurements or assumptions can be made about the volatility of the emitted species. We demonstrate the performance of this methodology by applying data from stir-frying experiments performed during the House Observations of Microbial and Environmental Chemistry (HOMEChem) campaign to a two-zone box model representing the UTest House. Preliminary estimates of organic mass emitted on a per-stir-fry basis for three types of organic aerosol factors are presented. Our analysis highlights that using traditional nonvolatile particle models and emission characterizations for some organic aerosol emitting activities can incorrectly attribute concentration changes to emissions rather than thermodynamic effects.

In modern society, ventilation is an important method for removing indoor particles. This study applies the parameter of attenuation index to analyse the effect of the removal of indoor particles in the two typical ventilation modes called ceiling exhaust and slit exhaust. Experiment was conducted in a chamber and riboflavin particles were used as the indoor particles source, instantaneous microbial detection (IMD) used to measure the particulate concentration. The results showed there was obvious concentration difference in the vertical distribution for the slit exhaust when indoor particles tended stable, and the smaller the particle size was, the more obvious the difference was. Air exchange rate (ACH) is an important factor affecting the indoor particle concentration distribution. In the process of indoor free settling (air exchange rate is 0 ACH), the sedimentation rate were 0.086 h −1 , 0.122 h −1 and 0.173 h −1 for the particles of 0.5–1.0 μm, 1.0–3.0 μm and 3.0–5.0 μm. When the air exchange rate increased to 2.5 ACH, the differences in the attenuation index is significant. There was also a significant linear relationship between air exchange rate and attenuation index. Furthermore, the effect of the slit exhaust mode on the removal of coarse particles is more remarkable as the increasing air exchange rate. [ABSTRACT FROM AUTHOR]

Two dynamical models, the traditional method of moments coupled model (MCM) and Taylor-series expansion method of moments coupled model (TECM) for particle dispersion distribution and gravitation deposition are developed in three-dimensional ventilated environments. The turbulent airflow field is modeled with the renormalization group (RNG) k – ε turbulence model. The particle number concentration distribution in a ventilated room is obtained by solving the population balance equation coupled with the airflow field. The coupled dynamical models are validated using experimental data. A good agreement between the numerical and experimental results can be achieved. Both models have a similar characteristic for the spatial distribution of particle concentration. Relative to the MCM model, the TECM model presents a more close result to the experimental data. The vortex structure existed in the air flow makes a relative large concentration difference at the center region and results in a spatial non-uniformity of concentration field. With larger inlet velocity, the mixing level of particles in the room is more uniform. In general, the new dynamical models coupled with computational fluid dynamics (CFD) in the current study provide a reasonable and accurate method for the temporal and spatial evolution of particles effected by the deposition and dispersion behaviors. In addition, two ventilation modes with different inlet velocities are proceeded to study the effect on the particle evolution. The results show that with the ceiling ventilation mode (CVM), the particles can be better mixed and the concentration level is also higher. On the contrast, with the side ceiling ventilation mode (SVM), the particle concentration has an obvious stratified distribution with a relative lower level and it makes a much better environment condition to the human exposure. [ABSTRACT FROM AUTHOR]

Atmospheric particulate samples were collected from four densely populated places in a university, and then the concentration levels of indoor particulates were analyzed. Water-soluble cations and anions in the indoor particles were analyzed through ultrasonic extraction and ion chromatography (IC), and total organic carbon (TOC) content was analyzed by using a TOC analyzer. Organic compounds in the indoor particles were analyzed through ultrasonic extraction and GC-MS. The results showed that among the water-soluble ions, the mass concentration of SO4-2 in indoor particles was the highest, so it was the main contributor of water-soluble anions, indicating that combustion of fossil fuels and industrial discharge were main sources of indoor particles at the four sampling points. Water-soluble organic carbon was the main component of water-soluble carbon in indoor particles. Among the four sampling points, the mass concentrations of the 18 organic compounds except for glycerol and phthalic acid were the highest in the cafeteria, so organic components in indoor atmospheric particles were mainly from food sources. [ABSTRACT FROM AUTHOR]

Many studies have been carried out on the environmental impact of the research stations on the Antarctic continent. However, the assessment of indoor air quality in these confined environments has been neglected. The main objectives of this study are to investigate the granulometric distribution of the indoor particles in the different compartments of the Brazilian Antarctic Station, to examine the number and mass concentration of the indoor particles, to conduct chemical and morphological analyses of the indoor PM2.5, and to identify the possible sources of the PM. The results showed that Na, K, Cl, Fe, Zn, S and Si were the main elements detected. High levels of black carbon were recorded in the workshop, which may be associated with the use of diesel vehicles. To identify the human activities related to the indoor particle emission in the station, the size distribution of the particles in the living room was monitored for seven consecutive days, during normal station operation. It was possible to identify the influence of individual processes, such as incineration, cooking and the movement of people, upon the particle size number concentration. The indoor/outdoor (I/O) ratio for the total suspended particles (TSP), PM10, PM2.5 and PM1 measured was significantly larger than those reported for urban buildings. In general, the I/O ratio distribution for all the compartments shows peak values between 2.5 and 10 μm, which is often related to human activity, such as cleaning, personnel circulation or clothing surfaces. The maximum I/O ratio at this range varied from 12 to 60. In addition, the compartments affected by combustion processes tend to present a significant number of submicron particles. [ABSTRACT FROM AUTHOR]

The transmission of airborne infectious diseases in indoor environments has become a major public health concern. Ultraviolet C lights are effective in inactivating bioaerosols to reduce infection risks. To facilitate the design and application of UVC systems, this study developed a modified irradiance model for calculating the spatial irradiance distribution when unstructured meshes are used for arbitrary reflective surfaces. With the modified irradiance model, the computational fluid dynamics (CFD)-Eulerian model was used to predict the dispersion and UV disinfection of bioaerosols. The proposed model was first preliminarily validated using measured data for in-duct ultraviolet germicidal lamps from the literature. For further validation of the proposed model in a relatively complex environment, experimental measurements of the detailed spatial irradiance distribution and bioaerosol concentration exhaled from a manikin in a ventilated chamber with a far UVC lamp were compared with calculated results. It was found that the proposed modified irradiance model can predict the spatial irradiance distribution reasonably well when unstructured meshes are used for arbitrary reflective surfaces. Furthermore, the modified irradiance model with the CFD-Eulerian model can predict the dispersion and UV disinfection of exhaled bioaerosols in indoor environments reasonably well. Finally, the validated model was used to predict person-to-person influenza A virus transport in a room with a ventilation rate of 3 ACH and a far UVC lamp with an effective output power of 0.34 W. The results show that the far UVC lamp can effectively reduce the receptor's exposure to influenza A virus by 65%. • A modified irradiance model was developed to predict spatial irradiance distribution. • Bioaerosol transport and UV disinfection model was validated by experimental data. • Person-to-person bioaerosol transport and far UVC disinfection was investigated. [ABSTRACT FROM AUTHOR]

To determine the composition of particulate matter (PM) in the indoor environments of four different types of archives (three naturally ventilated and one filtered), intensive size-resolved sampling was performed for four seasons of the year. For reconstituting indoor PM, nine aerosol components were considered. Organic matter was the dominant component of both fine and coarse fractions and represented approximately 50–80% of the PM. In the fine fraction, the next most abundant components were elemental carbon and sulphate, and in the coarse fraction the next most abundant were crustal matter, sulphate and nitrate. The resulting mass closure explained 95(±13)% and 115(±38)% of the gravimetric indoor PM in the fine and coarse size fractions, respectively. The results revealed that all the particles found indoors can be considered to be potentially threatening to the stored materials. The results also showed that the most important source of indoor PM in the naturally ventilated archives was penetration from the outdoor air, whereas in the filtered archive, the concentrations of particles were strongly reduced. In naturally ventilated archives the influence of domestic heating, road traffic and local sources (industrial pollution, camp fires) was observed. Furthermore, activities of the staff were identified as an indoor source of coarse particles in all archives. [ABSTRACT FROM AUTHOR]

Abstract: Background: Extensive epidemiological studies have provided evidence of an association between elevated outdoor particulate air pollution and adverse health effects. However, while people typically spend majority of time indoors, there is limited knowledge on airborne indoor particles and on the correlation between the concentrations of indoor particles and health effects. Even insights into the influence of differently sized indoor particles on human health are still rare. Objective: The association between differentially sized indoor air particles and the development of respiratory diseases was studied for three year aged children. Methods: Short-term measurements of particle mass and number concentrations were carried out in children''s rooms. Information on possible particle sources (smoking habits, type of heating, and traffic) and respiratory outcomes were obtained from questionnaires. Measured indoor particle concentrations were correlated with possible sources of indoor particles and with respiratory health impacts. Results: Daily smoking, smoking more than 5 cigarettes per day at home and traffic density in front of the window of children''s room were found to be related to indoor exposure by particles of different diameters. High indoor particle exposures were associated with an increased risk for the development of obstructive bronchitis and in some extent of non-obstructive bronchitis. The strongest impact was observed for the mass concentration of particles <1μm and the number concentration of particles >0.5μm. The risk increases still remain significant if tested for stability changing the number of adjustment variables or omitting randomly selected cases, respectively. Conclusion: Our results show significant associations between indoor particle concentrations and the risks for respiratory diseases in young children. The applied short-term measurements can help to assess the health risks of indoor particles with different sizes within epidemiological studies. [Copyright &y& Elsevier]

This study aims to evaluate whether indoor particles are associated with elevated blood pressure (BP) and heart rate (HR). We recruited 40 young, healthy students from universities in Taipei. We made four home visits in which we took consecutive 48-h measurements of systolic BP, (SBP) diastolic BP (DBP), and HR in each participant. Particulate matter less than 10 μm in diameter (PM10), 2.5 μm in diameter (PM2.5), and nitrogen dioxide levels were measured at each participant’s home. Participants were asked to keep their windows open during the first two visits, and keep their windows shut during the last two visits. We used linear mixed-effects models to associate BP and HR with indoor air pollutants averaged over 1- to 8-h periods prior to physiological measurements. We found indoor PM10 and PM2.5 exposures at 1- to 4-h means were associated with an elevation in SBP, DBP, and HR. Effects of indoor PM10 and PM2.5 on BP and HR were greatest during the visits with windows open. During windows-closed visits, participants showed no significant change in BP and HR with indoor PM10 exposure. We concluded that exposures to infiltrated outdoor particles are associated with short-term increases in BP and HR in young and healthy students. Closing windows can reduce indoor PM concentrations and modify the effect of PM10 on BP and HR in young adults. Practical Implications Particulate matter exposure, high blood pressure (BP) and heart rate (HR) have been reported to be associated with increased risk of cardiovascular morbidity and mortality. Exposure to indoor particles is found to be associated with Elevated BP and HR. Closing windows may reduce indoor particles concentrations and modify the effect of particles on BP and HR in young adults in heavily polluted cities. [ABSTRACT FROM AUTHOR]

We compared the school environment, asthma and allergy in 10 schools in Taiyuan, China, with eight schools in Uppsala, Sweden. In total 2193 pupils (mean age 13 years) participated. Chinese pupils had more respiratory symptoms, particularly daytime breathlessness after exercise (29.8% vs. 7.1%; P < 0.001), while cat allergy (1.2% vs. 6.6%; P < 0.001) and dog allergy (1.3% vs. 4.0%; P < 0.01) was less common. Cumulative incidence of asthma (1.8% vs. 9.5%; P < 0.001) and doctor's diagnosed asthma (1.2% vs. 9.0%; P < 0.001) were less common in China, indicating an under-diagnosis of asthma. Chinese classrooms were colder (mean 14.7 vs. 21.4°C), more humid (mean 42% vs. 31% RH) and had higher CO2-levels (mean 2211 vs. 761 ppm). Levels of cat (Fel d1), dog (Can f1) allergens were low in settled dust from China (<200 ng/g dust), but high in airborne dust on Petri-dishes (GM 16.8 ng/m2/day for Fel d1 and 17.7 for Can f1). The Swedish settled dust contained cat, dog and horse allergens in high levels (median 1300 ng/g, 1650 ng/g, 1250 U/g dust, respectively). In conclusion, there were large differences in the school environment, and in respiratory symptom and allergy. Allergen measurements in settled dust only may largely underestimate the classroom exposure. Practical Implications There is a need to improve the school environment, both in China and Sweden. The Swedish schools contained high levels of cat, dog and horse allergens and more amounts of open shelves and textiles that can accumulate dust and allergens. The air measurements indicated that Chinese schools may contain significant amounts of cat and dog allergen, and analysis of settled dust only may not reflect the true allergen exposure. Since the Chinese schools had no mechanical ventilation, they could not fulfill the ventilation standard in winter, and hence there is a need for improving the ventilation. The great discrepancy between respiratory symptoms and reports on asthma, and the high prevalence of attacks of breathlessness without wheeze, may have implication for future questionnaire studies on asthma in China. [ABSTRACT FROM AUTHOR]

From late 1999 to early March 2000, measurements of particle number (particles 0.01–20 μm in aerodynamic diameter) concentrations were made inside of a townhouse occupied by two non-smoking adults and located in Reston, VA (approximately 25 miles northwest of Washington, DC). The particle size measurements were made using an SMPSTM and an APSTM as well as a Climet optical scattering instrument. In this study, positive matrix factorization (PMF) was used to study the indoor particle size distributions. The size distributions or profiles obtained were identified by relating the obtained source contributions to the source information provided by the occupants. Nine particle sources were identified, including two sources associated with gas burner use: boiling water and frying tortillas. Boiling water for tea or coffee was found to be associated only with the smallest particles, with a number mode close to the detection limit of the SMPS (i.e., 0.01 μm). Frying tortillas produced particles with a number mode at about 0.09 μm while broiling fish produced particles with a number mode at about 0.05 μm. A citronella candle was often burned during the study period, and this practice was found to produce a 0.2- μm modal number distribution. Other indoor particle sources identified included sweeping/vacuuming (volume mode at 2 μm); use of the electric toaster oven (number mode at 0.03 μm); and pouring of kitty litter (volume mode over 10 μm). Two outdoor sources were also resolved: traffic (number mode at about 0.15 μm) and wood smoke (major number mode at about 0.07 μm). The volume distributions showed presence of coarse particles in most of the resolved indoor sources probably caused by personal cloud emissions as the residents performed the various indoor activities. Practical Implications This study has shown that continuous measurements of indoor particle number and volume concentrations together with records of personal activities are useful for indoor source apportionment models. Each of the particle sources identified in this study produces distinct size distributions that may be useful in studying the mortality and morbidity effects of airborne particulate matter because they will have different penetrability and deposition patterns. [ABSTRACT FROM AUTHOR]

Abstract: A new drift–flux model for particle distribution and deposition in indoor environments is developed. Gravitational settling and deposition are examined thoroughly and the model is applied to simulate particle distribution and deposition in a ventilated model room. The turbulent airflow field is modeled with the renormalization group (RNG) k–ε turbulence model. For the particulate phase, the concentration field is divided into two regions, the core region and the concentration boundary layer. The concentration distribution in the core region is obtained by solving a three-dimensional particle transport equation. Deposition flux towards the wall is determined with a semi-empirical particle deposition model. With the feasibility of the proposed Eulerian model, the influences of the other deposition mechanisms can be captured easily into the model. The model is validated experimentally and a good agreement between numerical and experimental results is found. Inferring from the result, it shows that the well-mixed assumption cannot hold for coarse particles. The model presented in the current work provides an efficient and reliable tool for investigation of spatial and temporal particle concentration in enclosures and the result will be very useful for improving our current understanding of human exposure assessment. [Copyright &y& Elsevier]

Diurnal variation of indoor submicrometer (0.007–0.808 μm) particle number and particle mass (approximation of PM2.5) concentrations was investigated in 15 houses in a residential suburb of Brisbane during winter in 1999. Continuous monitoring for more than 48 h was conducted using a condensation particle counter (CPC) and a photometer (DustTrak) in the kitchen of each house, and the residents kept diaries of the activities conducted. In addition, data from a central monitoring station was used to investigate indoor/outdoor relationships. The results show that there were clear diurnal variations in both particle number and approximation of PM2.5 concentrations, for all the investigated houses. The pattern of diurnal variations varied from house to house, however, there was always a close relationship between the concentration and human indoor activities. The average number and mass concentrations during indoor activities were (18.2±3.9)×103 particles cm−3 and (15.5±7.9) μg m−3, respectively, and under non-activity conditions, (12.4±2.7)×103 particles cm−3 (11.1±2.6)±μg m−3, respectively. In general, there was a poor correlation between mass and number concentrations and the correlation coefficients were highly variable from day to day and from house to house. This implies that conclusions cannot be drawn about either one of the number or mass concentration characteristics of indoor particles, based on measurement of the other. The study also showed that it is unlikely that particle concentrations indoors could be represented by measurements conducted at a fixed monitoring station due to the large impact of indoor and local sources. [Copyright &y& Elsevier]

Enhanced soiling is frequently observed near the multi-slot cabin supply air nozzles in twin-aisle commercial airplanes, which would increase the cleaning and maintenance costs. This study proposed a computer-aided design approach to develop a new cabin supply air nozzle for reducing particle deposition in commercial airplanes. In the new nozzle, the slot dividers were removed to reduce particle deposition, while the shape of the plenum was re-designed using computational fluid dynamics (CFD) to ensure supply air uniformity. The new nozzles were fabricated using a 3D printing technique. The performance of the new cabin supply air nozzles was compared with that of the original multi-slot nozzles by both experimental measurements and numerical simulations, in terms of supply air velocity distribution, particle deposition, pressure drop, noise level, and weight. The results show that the new cabin supply air nozzles can significantly reduce particle deposition on the target surface in comparison to the original multi-slot nozzles, while providing similar airflow and temperature distributions in the aircraft cabin. Furthermore, the new nozzles exhibited better supply air uniformity, lower pressure drop, lower noise level, and were lighter in weight than the original multi-slot nozzles. • A computer-aided design approach was proposed to develop a new cabin supply air nozzle. • The new cabin supply air nozzles can significantly reduce particle deposition. • The new nozzles had better supply air uniformity, lower pressure drop, and lighter weight. [ABSTRACT FROM AUTHOR]

Enhanced soiling due to particle deposition is often observed around multi-slot cabin supply air nozzles in commercial airplanes. This study aimed to investigate the influence of surface roughness on the particle deposition distribution around multi-slot cabin supply air nozzles of commercial airplanes. This investigation constructed a half-row cabin mockup installed with three 3D-printed supply air nozzles of a twin-aisle commercial airplane. A cutting method was proposed to measure the detailed particle deposition velocity distribution on the target surface of the nozzles covered by different grades of sandpaper with different roughness heights. This study also conducted numerical calculations for the particle deposition velocity distribution using an Eulerian particle deposition model. Both the experimental and modeling results show that strong particle deposition occurred on the cut samples near the slot dividers. When the surface roughness height was greater than or equal to 6 μm, the particle deposition velocity increased significantly with the surface roughness height. However, when the surface roughness height was less than or equal to 3 μm, the particle deposition velocity was relatively insensitive to the surface roughness. The analysis indicated that polishing the surfaces of cabin supply air nozzles may not effectively solve the problem of enhanced soiling in the aircraft cabin. • Influence of surface roughness on particle deposition around cabin supply air nozzles was investigated. • Strong particle deposition occurred on the surface areas near the slot dividers. • When roughness height was small, particle deposition velocity was insensitive to surface roughness. [ABSTRACT FROM AUTHOR]

Outdoor aerosols experience environmental changes as they are transported indoors, including outdoor-to-indoor temperature and mass-loading gradients, which can reduce or enhance their indoor concentrations due to repartitioning driven by changes in thermodynamic equilibrium states. However, the complexity required to model repartitioning typically hinders its inclusion in studies predicting indoor exposure to ambient aerosols. To facilitate exposure predictions, this work used an explicit thermodynamic indoor aerosol model to simulate outdoor-to-indoor aerosol repartitioning typical for residential and office buildings across the 16 U.S. climate zones over an annual time horizon. Results demonstrate that neglecting repartitioning when predicting indoor concentrations can produce errors of up to 80-100% for hydrocarbon-like organic aerosol, 40-60% for total organic aerosol, 400% for ammonium nitrate, and 60% (typically 3 μg/m 3 ) for the total PM 2.5 aerosol. Underpredictions were more likely for buildings in hotter than colder regions, and for residences than offices, since both cooler indoor air and more meaningful residential organic aerosol concentrations encourage condensation of semivolatile organics. Furthermore, a method for computing correction factors to more easily account for thermodynamic repartitioning is provided. Applying these correction factors to mechanical-only aerosol predictions significantly reduced errors to <0.5 μg/m 3 for the total indoor PM 2.5 while bypassing explicit thermodynamic simulations.

The intensity, frequency, duration, and contribution of distinct PM 2.5 sources in Asian households have seldom been assessed; these are evaluated in this work with concurrent personal, indoor, and outdoor PM 2.5 and PM 1 monitoring using novel low-cost sensing (LCS) devices, AS-LUNG. GRIMM-comparable observations were acquired by the corrected AS-LUNG readings, with R 2 up to 0.998. Twenty-six non-smoking healthy adults were recruited in Taiwan in 2018 for 7-day personal, home indoor, and home outdoor PM monitoring. The results showed 5-min PM 2.5 and PM 1 exposures of 11.2 ± 10.9 and 10.5 ± 9.8 µg/m 3 , respectively. Cooking occurred most frequently; cooking with and without solid fuel contributed to high PM 2.5 increments of 76.5 and 183.8 µg/m 3 (1 min), respectively. Incense burning had the highest mean PM 2.5 indoor/outdoor (1.44 ± 1.44) ratios at home and on average the highest 5-min PM 2.5 increments (15.0 µg/m 3 ) to indoor levels, among all single sources. Certain events accounted for 14.0%-39.6% of subjects' daily exposures. With the high resolution of AS-LUNG data and detailed time-activity diaries, the impacts of sources and ventilations were assessed in detail., (© 2020 The Authors. Indoor Air published by John Wiley & Sons Ltd.)