Indoor Particle Concentrations Research Articles

Investigating the impact of filters on long-term particle concentration measurements in residences (RP-1649)

Filters in heating, ventilation, and air-conditioning (HVAC) systems are the most prevalent air cleaning method in residential environments in North America. This study evaluated the long-term impact of residential filtration systems on indoor particle concentrations by examining concentration measurements from low-cost monitors over one year in twenty homes in Toronto, Ontario, Canada. These concentration results suggested that in general, indoor concentration had a similar seasonal trend as the ambient concentration, and indoor activities (e.g., cooking) elevated indoor particle levels for 40-50% of the time. Further, the impacts of electret filters were examined using a non-electret filter with a minimum efficiency reporting value (MERV) of 8 as the reference point at each home. The mean effectiveness of the filters (MERV 8E = −4.19%, MERV 11E = −0.51%, and MERV 14E = 14.5%) were lower than values found in the literature, most likely due to lower HVAC system runtime in our sample of homes (median = 9.6%). Overall, this filter effectiveness analysis reveals that the real-life filter performance was strongly influenced by system and house characteristics (e.g., system runtime, in-situ efficiency, air change rate, and particle source strength), and thus can be different from modeling and laboratory test results.

Filtration efficiency and ventilation performance of window screen filters

Efficient natural ventilation is an important approach to maintaining indoor air quality. However, owing to the increasing concentration of outdoor particulate matter (PM), natural ventilation without filtration results in the introduction of outdoor particles in buildings, thus increasing indoor exposure to PM. Indoor PM concentration is determined by the particle removal efficiency of window screen filters. In this study, using an experimental chamber and an actual building, the particle removal performance of window screen filters was evaluated for their potential application. To investigate the relationship between the outdoor and indoor concentrations of particles with diameter size ≤ 2.5 μm (PM2.5), and to evaluate the efficiency of the window screen filters in removing such particles, the window screen filters were installed in a full-scale test room. The results obtained showed that the average PM2.5 indoor/outdoor (I/O) ratio was within the range 0.24–0.72, and varied with the performance of the window screen filter. An analysis of the correlation between the ventilation rate and the air exchange rate (AER) showed that the I/O ratio increased as AER increased. Additionally, the particle size removal efficiency (PSE) of the window screen filters varied considerably with increasing particle diameter (0.3–10.0 μm), ranging from 0 to 82.4%, and the PSE results showed trends that were similar to those of PM2.5 removal efficiency based on the measurements performed in the test room. Therefore, window screen filters can be used to reduce the indoor concentration of outdoor particles.

Effect of enhanced supply air filtration in buildings on protecting citizens from environmental radioactive particles

The effect of enhanced filtration on protection citizens staying indoor against airborne radionuclides released during nuclear core melt accidents was determined by field measurements using outdoor particles as simulants. An electrically enhanced filter was installed in the HVAC system of an office building and its removal efficiency for particles was altered by using a separate particle charging section in power on and off positions. The effect of air filtration on indoor particle concentrations was determined by using an automated measurement system which was continuously sampling from the outdoor air, filtered supply air and exhaust air. With the aid of the measured outdoor and modelled indoor concentrations the indoor/outdoor ratio of particles of outdoor origin could be accurately determined. External charging of the particles increased the electret filters removal efficiency for 0.4 µrn size particles from 60% to 95%, resulting in decrease of the average I/O ratio of the same size particles from 0.67 to 0.40. Despite the high improvement in the supply air filtration efficiency the indoor concentrations decreased only modestly which is likely due to the leaky construction of the building, demonstrating the detrimental effect of air infiltration on the protection provided by buildings against outdoor airborne hazards. Practical implications: The developed method allows quantification of the key parameters affecting the protection of buildings against outdoor contaminants, thus allowing accurate estimation of size resolved indoor to outdoor ratios for fine particles. The electrically enhanced filter can remove effectively also submicron particles thus reducing the occupant exposure to outdoor hazardous or harmful materials. Best results can be achieved with airtight buildings.

Study on the Influence of Air Tightness of the Building Envelope on Indoor Particle Concentration

In order to grasp the building palisade structure tightness of indoor particulate matter mass concentration based on the particle penetration mechanism and settlement characteristics, this article analyzes the measurements of two different types of building air tightness of a Shenyang university office building in terms of indoor and outdoor particulate matter mass concentration levels from 2016-1-09 to 1-22, 2016-7-18 to 8-03, and 2017-2-28 to 3-13. The building outside the closed window that had no indoor source condition, the indoor office building and outdoor particle mass concentration, and the aperture size and shape of the envelope were analyzed to carry on the numerical simulation research by Fluent software, which was then analyzed; the results reveal that the measuring point of the I/O ratio is less than point B of the I/O ratio, measurement points of A linear regression fitting degree is lower than the fit of the measuring point B, and the causes for the measuring point A tightness (level 8) is superior to the measuring point B (level 4). When the gap height h is greater than 0.5 mm, the penetration rate of particles within the range of 0.25–2.5 μm particle size is close to 1. In different gap depths, the penetration rate of particles within the range of 0.1–1 μm particle size was close to 1. In diverse pressure difference, the 0.25–2.5 μm particles within the scope of penetration rate P is close to 1, the gap on both sides of the differential value ΔP; the greater the particle, the higher penetration rate. The larger the right-angle number of gap n, the lower the penetration rate of particles. The L-shaped gap and U-shaped gap have significantly better barrier effects in larger and smaller particles than the rectangular gap. The research results in this paper can help people understand and effectively control the influence of outdoor particles on the indoor air quality and provide reference data for the prediction of indoor particle mass concentration in buildings, which has theoretical basis and practical significance.

Feature analysis of indoor particulate matter concentration using fiber filtration for mechanical ventilation

Experiments and theoretical analyses are conducted in an office in Xi’an to study indoor particle concentration through establishing a mass balance equation and real-time monitoring. Meanwhile, the filtration efficiencies for different grades of filter media have been tested and verified by experiments. Studies are conducted on indoor particulate emission source and concentration change in combination with equation of linear regression, linear fitting curve of indoor–outdoor concentration, as well as indoor concentration decay profile. The results indicate that coarse filters G1 to G4 are used in mechanical ventilation to filter larger particles. However, it can only achieve 1.6%–15.2% for PM2.5 filtration efficiency. On the other hand, F7 to H10 filters could reach the high efficiency of 55.6%–69.7%. Furthermore, indoor PM2.5 concentration with a coarse filter using G4 filter can obviously reduce the indoor particulate concentration to 69–75 μg/m3. It ranges from 87 to 90 μg/m3 using a G3 filter, while the outdoor PM2.5 concentration is 135–150 μg/m3.

Cooking and electronic cigarettes leading to large differences between indoor and outdoor particle composition and concentration measured by aerosol mass spectrometry.

We spend about two thirds of our time in private homes where airborne particles of indoor and outdoor origins are present. The negative health effects of exposure to outdoor particles are known. The characteristics of indoor airborne particles, though, are not well understood. This study assesses the differences in chemical composition of PM1 (<1 μm) inside and outside of an occupied Swedish residence in real time with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and an Aethalometer. The chemical composition and concentration of particles indoors showed large differences compared to outdoors. The average indoor concentration was 15 μg m-3 and was higher than the outdoor 7 μg m-3. Organics dominated indoor particle composition (86% of the total mass) and originated from indoor sources (cooking, e-cigarette vaping). The average indoor to outdoor ratios were 5.5 for organic matter, 1.0 for black carbon, 0.6 for sulphate, 0.1 for nitrate, 0.2 for ammonium and 0.2 for chloride. The occupancy time accounted for 97% of the total measured period. Four factors were identified in the source apportionment of organic particle fraction by applying positive matrix factorization (PMF): two cooking factors, one e-cigarette factor and one outdoor contribution (OOA) organic factor penetrated from outside.

Indoor Particle Concentrations, Size Distributions, and Exposures in Middle Eastern Microenvironments

There is limited research on indoor air quality in the Middle East. In this study, concentrations and size distributions of indoor particles were measured in eight Jordanian dwellings during the winter and summer. Supplemental measurements of selected gaseous pollutants were also conducted. Indoor cooking, heating via the combustion of natural gas and kerosene, and tobacco/shisha smoking were associated with significant increases in the concentrations of ultrafine, fine, and coarse particles. Particle number (PN) and particle mass (PM) size distributions varied with the different indoor emission sources and among the eight dwellings. Natural gas cooking and natural gas or kerosene heaters were associated with PN concentrations on the order of 100,000 to 400,000 cm−3 and PM2.5 concentrations often in the range of 10 to 150 µg/m3. Tobacco and shisha (waterpipe or hookah) smoking, the latter of which is common in Jordan, were found to be strong emitters of indoor ultrafine and fine particles in the dwellings. Non-combustion cooking activities emitted comparably less PN and PM2.5. Indoor cooking and combustion processes were also found to increase concentrations of carbon monoxide, nitrogen dioxide, and volatile organic compounds. In general, concentrations of indoor particles were lower during the summer compared to the winter. In the absence of indoor activities, indoor PN and PM2.5 concentrations were generally below 10,000 cm−3 and 30 µg/m3, respectively. Collectively, the results suggest that Jordanian indoor environments can be heavily polluted when compared to the surrounding outdoor atmosphere primarily due to the ubiquity of indoor combustion associated with cooking, heating, and smoking.

Exposure to traffic related pollution in buildings – a risk factor approach

TPS 901: Indoor air pollution, Exhibition Hall, Ground floor, August 28, 2019, 3:00 PM - 4:30 PM Air pollution is a growing concern among the general public. Air quality is not only an issue outdoors. The local outdoor air quality also affects the air quality indoors, where we spend about 90% of our time. In buildings close to busy roads indoor particle concentrations can reach high levels, which is a risk for the health of the occupants. Poor air quality mainly affects young children, since their lungs are still developing. Moreover, the health of vulnerable elderly is affected. In order to improve their living environment understanding of the exposure risk in kindergartens, schools and nursing homes near busy roads is required. We developed a methodology to estimate the risk of exposure to traffic related pollution in buildings. Based on literature survey and practical experience we defined risk factors for exposure to traffic related pollution indoors. These risk factors can be grouped in the following six themes: a)situation and outdoor sources, e.g. traffic intensity, congestion, urban canyon, urban canopy, other sources. b)exposure paths - outdoor spaces, e.g. distance from the road, type of use. c)exposure paths - building envelope, e.g. air tightness. d)exposure paths - ventilation, e.g. filter quality, location of the outdoor air inlet. e)maintenance, e.g. frequency of filter changes. f)use, e.g. use of the ventilation system, airing, awareness of the outdoor air quality. The risk factor approach has been used to investigate the risk of exposure to traffic related pollution in 61 kindergartens, schools and nursing homes in the region of The Hague that are situated at a location with a high intensity traffic. The results were used to give protective measures, including simple improvements focussed on user behaviour or maintenance, as well as more complex technical interventions.

Infiltration of fine particles in urban buildings

Singapore is a tropical country that can be affected by outdoor fine particle air pollution. Little information is available on the penetration of outdoor fine particles into daycare environments. Our study attempted to address the following objectives: to measure indoor infiltration factor (Finf of PM2.5 from outdoor fine particles and to determine the building parameters that modifies the indoor PM2.5. We collected indoor/outdoor 1-min PM2.5. from 50 daycare environments. We noted high indoor and outdoor concentrations of fine particles due to the presence of regional haze pollution. Indoor and outdoor fine particle concentrations are significantly highest for daycares located near highways while indoor to outdoor ratios were significantly lower for air-conditioning use in daycares. Mean Finf±SD of 0.65±0.19 in daycare rooms which are naturally ventilated and lower Finf±SD values of 0.46±0.22 for those that are air-conditioned. The penetration coefficients and air exchange rates were higher in naturally ventilated daycares (0.78 vs 0.61 and 1.47 vs 0.86 h−1 respectively). Our findings show that children remaining indoor in daycares where air conditioning is used can reduce PM2.5 exposures during outdoor pollution episodes.

Site- and house-specific and meteorological factors influencing exchange of particles between outdoor and indoor domestic environments

The aim of this study was to investigate the influence of site- and house-specific as well as meteorological factors on indoor and outdoor particle concentrations. Particle number (PN) and particle mass (PM) concentrations were monitored in 62 houses in Brescia, Northern Italy, during two winter monitoring periods. Measurements were conducted in houses of non-smokers and without the activation of any internal aerosol sources from domestic activities such as cooking and cleaning. Indoor and outdoor particle concentrations were measured for 30 min in each house. A wide-range aerosol spectrometer (MINIWRAS 1371, GRIMM) was used to detect 41 classes of particles from 10 nm to 35 μm. The effects of natural ventilation on indoor particle concentrations were also considered by measuring PM and PN indoor/outdoor ratios before and after a window was opened for a period of 15 min. An ANOVA analysis was performed on a sub-dataset of 35 houses to evaluate the dependence of PN and PM concentrations on site- and house-specific as well as meteorological factors. The house energy class was significantly related to indoor particle concentrations, and window dimensions seemed to influence the concentrations both before and after the ventilation period. We found that some factors, e.g., the floor level, need further investigation.

Size-resolved surface deposition and coagulation of indoor particles

ABSTRACTThis study aimed to investigate the influence of surface deposition and coagulation on indoor particles larger than 0.25 μm by conducting tests in a room-sized enclosed chamber under different air temperatures. The particles, processed dust intercepted by indoor air conditioners, were generated using an aerosol generator. The deposition rate and coagulation coefficients were used to estimate the efficiency of indoor particle surface deposition and coagulation in this study. The results show that the deposition rates increase as the air temperature rises, and high temperatures can also increase the coagulation coefficient. In addition, test results show that the enhancement of indoor air mixing intensity can increase both the deposition rates and the coagulation efficiencies. The contribution of coagulation to the total decay of indoor particle concentrations decreases over time, and the contribution is higher for particles in the range of 0.25–0.5 μm than those in the range of 0.5–1.0 μm.

Indoor Air Pollution Related Respiratory Ill Health, a Sequel of Biomass Use

Introduction: Climate change may worsen existing indoor air problems and create new problems by altering outdoor conditions that affect indoor conditions. Since climate change is due to both natural variability and human-induced contributions, public health professionals through their expertise in health promotion and behavior change can play a vital role in promoting lifestyle choices that will decrease greenhouse gas emissions. This study, therefore, aims at presenting the health effects of indoor air pollutants from biomass use. Methods: A cross sectional study involving 1,170 consenting women was conducted in Masaiti and Ndola districts of Zambia. Data collection tools included a structured questionnaire; foobot (indoor air quality monitoring device) and spirometer (lung function test device). Data was analyzed using SPSS version 16 and analyses were done at Univariate, bivariate and multivariate level at 5% statistical significant level. Results: Population using biomass as cooking fuel was 69.2%. Indoor particulate (PM2.5) overall median (Q1, Q2) distribution during cooking period was 501(411, 686) μg/m3 and daily average was 393(303,578) μg/m3 while VOC daily average was 343(320, 363) ppb. The proportion of women with respiratory symptoms and impaired lung functions was higher in households with high levels of indoor pollutants. There was a statistically significant association between mean indoor particulate concentration levels and the number of maternal respiratory symptoms. There was a significant association between indoor VOC and forced vital capacity (p=0.011). Conclusion: The results contribute to the growing evidence regarding the effect of biomass use on indoor air quality and consequent adverse respiratory health outcomes.

Study on Influencing Mechanism of Outdoor Plant-related Particles on Indoor Environment and its Control Measures during Transitional Period in Nanjing

ABSTRACT Most city trees in Nanjing are Platanus acerifolia and Populus nigra, which generate many whirling willow catkins in the air during the transitional season, yet little attention has been paid to the health risks, including itchy skin and respiratory infections, on occupants of roadside buildings. Since the air quality of these indoor spaces cannot meet WHO guidelines during the transitional season due to the influence of plant pollutants, a suitable ventilation scheme, together with air filtration measures, is urgently needed. Hence, four ventilation schemes were compared: natural ventilation, no ventilation with the door and windows closed, recirculating ventilation with a ceiling cassette fan-coil unit but no air filter, and recirculating ventilation with a ceiling cassette fan-coil unit and F7 filter. The performance of these modes was evaluated by comparing the effects of outdoor particulate matter on the indoor air quality. The results showed that the larger the particle size, the lower the I/O ratio. Furthermore, the influence of the occupants’ activities on indoor particle concentrations cannot be ignored, particularly for large particles, which varied more than small particles according to indoor human activity. Therefore, we suggest operating the ceiling cassette fan-coil unit with an air filter for this application, which can reduce the indoor particle concentration to an acceptable level and decrease the potential health risk posed by plant pollutants.

Comfort IAQ – a new tool to simulate the indoor particulate matter pollution in relation to the chosen supply air filter quality

Many factors are rather well known for their ability to create a good indoor air climate, but when it comes to airborne particles, there is no great deal of documentation to consult and set requirements. Nor are there much of other specific guidelines. The new, product-neutral and free online calculation tool Comfort IAQ helps to understand the mechanisms behind IAQ and gives a good indication on what would be the impact on indoor air quality (IAQ) due to air exchange, outdoor air environment, air filter selection and building envelope characteristics. Comfort IAQ allows to simulate the concentrations of Particulate Matter (PM1, PM2.5, PM10) in a specific ventilated room, depending on the chosen supply air filter quality. To model the room and the supply air conditions in a realistic way, Comfort IAQ allows to define besides outdoor air conditions (ODA) also the room dimensions, the air changes, the recirculation air rate as well as the supply air filter quality (based on ISO 16890, EN779 or ASHRAE 52.2). Based on these values, the Comfort IAQ tool provides an estimation of the indoor particle concentration and gives engineers and planers a good tool to optimize the Indoor Air Quality, by choosing the best combinations of supply air filter qualities and ventilation rates for a specific application. The algorithms in the online tool Comfort IAQ have been developed by Lars Ekberg, (Docent-installallationsteknik, Chalmers Tekniska Högskola) and the accuracy of the calculations was verified by comparing them with measurements in a full-scale test chamber.

The influence of ventilation mode and personnel walking behavior on distribution characteristics of indoor particles

People spend nearly 90% of their time daily in various indoors, hence indoor environment is important for mortal survival and activity, which affected human health directly. Indoor particulate pollution has become an issue of increasing concern for human beings. Personnel walking behavior and ventilation mode will significantly affect the transfer characteristics of indoor particles. This paper analyzes the effect of walking process on indoor particle resuspension, and different ventilation modes (ceiling exhaust and slit exhaust) on the removal of indoor particulate concentration in experimental and theoretical models. The results show that the particle diffusion model under walking is in good agreement with the experimental results. The particles with different sizes have different diffusion characteristics during walking due to the surface deposition and resuspension rate. Particles of 1.0–3.0 μm have the fastest velocity and the largest amount in suspension, while the smallest for 0.5–1.0 μm particles. Different ventilation modes have different effects on the removal of indoor particles. The particles attenuation index is higher under slit exhaust mode, therefore the ventilation effect is higher than ceiling ventilation mode.

Study on the multivariate prediction model and exposure level of indoor and outdoor particulate concentration in severe cold region of China

Atmospheric particulate matter( PM10, PM2.5) has been the main pollutant in most cities of China in recent years, and the exposure concentration is related to the incidence of human diseases and mortality. The time spent indoors is more than 80% for modern people. Therefore, study on the correlation and exposure level of indoor and outdoor atmospheric particles is important. To research the exposure level in the heating season and non-heating season of indoor and outdoor particulate concentration in severe cold region of China, a total of 110 samples of four types of buildings (office, classroom, urban residence and rural residence) in Daqing, a typical city of severe cold region in China, were tested by particle monitor. Based on the indoor and outdoor environmental parameters, multiple linear regression (MLR) and principal component regression (PCR), established the indoor particulate concentration prediction models. The short and long term exposure of different people in different environments in severe cold region of China was analyzed based on the people's time-activity pattern with the measured data and model. The results showed that as for the short term indoor and outdoor exposure of different people, the average combined exposure of urban people in heating season is 60.0% higher than that in non-heating season, and rural people in heating season 30.2% higher than that in non-heating season. As for the long term indoor and outdoor exposure of different people, the annual average combined exposure of urban people was 9.6% higher than that of rural people. While all for urban and rural people, differences in respiratory rates between genders resulted in an average potential dose of 21. 8% higher in male than in female.

How Outdoor Trees Affect Indoor Particulate Matter Dispersion: CFD Simulations in a Naturally Ventilated Auditorium.

This study used computational fluid dynamics (CFD) models, coupling with a standard k-ε model based on the Reynolds-averaged Navier-Stokes (RANS) approach and a revised generalized drift flux model, to investigate effects of outdoor trees on indoor PM1.0, PM2.5, and PM10 dispersion in a naturally ventilated auditorium. Crown volume coverage (CVC) was introduced to quantify outdoor trees. Simulations were performed on various CVCs, oncoming wind velocities and window opening sizes (wall porosities were 3.5 and 7.0%, respectively, for half and fully opened windows). The results were as follows: (1) A vortex formed inside the auditorium in the baseline scenario, and the airflow recirculation created a well-mixed zone with little variation in particle concentrations. There was a noticeable decrease in indoor PM10 with the increasing distance from the inlet boundary due to turbulent diffusion. (2) Assuming that pollution sources were diluted through the inlet, average indoor particle concentrations rose exponentially with increasing oncoming wind speed. PM10 changed most significantly due to turbulent diffusion and surface deposition reduction intensified by the increased wind velocity. (3) Increasing the window opening improved indoor cross-ventilation, thus reducing indoor particle concentrations. (4) When 2.87 m3/m2 ≤ CVC ≤ 4.73 m3/m2, indoor PM2.5 could meet requirements of the World Health Organization’s air quality guidelines (IT-3) for 24-hour mean concentrations; and (5) average indoor particle concentrations had positive correlations with natural ventilation rates (R2 = 0.9085, 0.961, 0.9683 for PM1.0, PM2.5, and PM10, respectively, when the wall porosity was 3.5%; R2 = 0.9158, 0.9734, 0.976 for PM1.0, PM2.5, and PM10, respectively, when the wall porosity was 7.0%).

Effect of Reducing Fine Particle Concentration after Use of Air Purifiers in Hospital: Preliminary Results

Most hospitals have air-conditioning facilities, but many people are moving, and there are many indoor air pollutants such as fine particle. In this study, air purifier is installed in hospital ward to investigate the improvement of indoor air pollution. We installed 25 air purifiers in 4th floor ward of a university hospital in Seoul, Republic of Korea. The air purifier filter is turned on and off at intervals of 4 weeks, and the indoor fine particle concentration is continuously measured through the dust sensors of the air purifiers. We obtained the outdoor fine particle data from the nearest Air Korea measuring station. We compared indoor fine particle concentrations before and after using the air purifier and compared those after stratification of the types of place (single rooms, rooms with five or six beds, nurse stations, and patient rest room). We also analyzed the average difference and correlation between indoor and outdoor fine particle concentrations. After the use of air purifiers, the difference of indoor and outdoor fine particles concentrations are larger and the correlation between outdoor and indoor fine particle was also lower than that before the use of air purifiers. The average difference of indoor fine particle before and after use of air purifier was about 3.46-5.68 &amp;#956;g/m3. Among the four types of places, the nurse stations had the highest concentration of fine particles, the lowest patient rest room, and there was a difference between the groups.Despite having air conditioning facilities in the hospital, indoor fine particle concentration was lower when air purifiers was used than before use of air purifiers. Particularly in places where people are moving a lot in the ward, fine dust is high. Therefore, additional efforts are needed to lower the concentration of fine particle in hospitals such as use of air purifiers.

Effects of source emission and window opening on winter indoor particle concentrations in the severe cold region of China

Indoor particles are affected by both indoor particle sources and outdoor particles penetrating into the indoor environment. Some human behaviors such as opening windows, cooking, and smoking influence indoor air quality strongly. Indoor particle sources increase the indoor particle concentrations by generating considerable amounts of particulate matters. Opening windows can increase the exchange efficiency of indoor and outdoor particles. In this study, the effects of indoor particle source emission and opening a window on indoor particle concentrations were estimated for the severe cold region of China using tests in a room-size chamber. Indoor and outdoor fine particulate matter (PM2.5) mass concentrations and particle number concentrations from 0.3 to 10 μm were measured simultaneously in different test conditions. An indoor source was simulated using an aerosol generator to discharge dust, which was intercepted by indoor air conditioners. Indoor particle concentrations increased rapidly when the indoor source was active, and longer emission time led to greater growth. After ending indoor particle emission, indoor particle concentrations decreased due to infiltration and deposition, and opening the window can promote that decrease. Decay rates were greater for 2.5–10 μm particles because loss by gravitational settling is dominant for larger particles. When the window was opened, particle decay rates became extremely high; up to 19.09 h−1 for 2.5–10 μm particles and up to 9.73 h−1 for PM2.5.

Indoor particle dynamics in a school office: determination of particle concentrations, deposition rates and penetration factors under naturally ventilated conditions.

Recently, the problem of indoor particulate matter pollution has received much attention. An increasing number of epidemiological studies show that the concentration of atmospheric particulate matter has a significant effect on human health, even at very low concentrations. Most of these investigations have relied upon outdoor particle concentrations as surrogates of human exposures. However, considering that the concentration distribution of the indoor particulate matter is largely dependent on the extent to which these particles penetrate the building and on the degree of suspension in the indoor air, human exposures to particles of outdoor origin may not be equal to outdoor particle concentration levels. Therefore, it is critical to understand the relationship between the particle concentrations found outdoors and those found in indoor micro-environments. In this study, experiments were conducted using a naturally ventilated office located in Qingdao, China. The indoor and outdoor particle concentrations were measured at the same time using an optical counter with four size ranges. The particle size distribution ranged from 0.3 to 2.5μm, and the experimental period was from April to September, 2016. Based on the experimental data, the dynamic and mass balance model based on time was used to estimate the penetration rate and deposition rate at air exchange rates of 0.03-0.25h-1. The values of the penetration rate and deposition velocity of indoor particles were determined to range from 0.45 to 0.82h-1 and 1.71 to 2.82m/h, respectively. In addition, the particulate pollution exposure in the indoor environment was analyzed to estimate the exposure hazard from indoor particulate matter pollution, which is important for human exposure to particles and associated health effects. The conclusions from this study can serve to provide a better understanding the dynamics and behaviors of airborne particle entering into buildings. And they will also highlight effective methods to reduce exposure to particles in office buildings.