Indoor Particle Number Concentrations Research Articles

High-frequency electric knife smoke particles: An experimental study on factors influencing emission characteristics

During surgery, the use of a high-frequency electric knife produces smoke, which can be harmful to the health of indoor medical staff and patients. The quantity and particle size distribution of smoke particles produced by different tissues may vary. Understanding the release characteristics of these smoke particles is necessary to clarify their impact on the surgical environment and to seek effective smoke control methods. A previous comparative analysis of human and pig tissues revealed that they share similar water and fat compositions in certain anatomical regions. In this study, we investigated the emission characteristics of smoke particles from various tissues of pigs (skeletal muscle, liver, kidney, skin, and subcutaneous fat) under different operating powers of an electric knife. We measured the indoor particle number concentration (particle concentration), and estimated the PM2.5 mass concentration (PM2.5 concentration), particle size distribution, and emission rate of the smoke particles. The study obtained the particle emission rates of different tissues under different electric knife operating powers, results of which showed that (1) during the operation of the electric knife, mainly small particles below 1 μm are produced. Among them, particles of 0.3 μm were the most abundant, with a particle concentration level of up to 109 particles/m3, accounting for 85.17–97.64% of the total particle number, and as the particle size increased, the particle concentration and percentage decreased significantly. (2) The water and fat compositions of different tissues influenced the indoor particle concentration and emission rate of the smoke emitted by the electric knife. Among different tissues, subcutaneous fat tissue had the lowest particle concentration and emission rate. (3) The electric knife operating power mainly affected particles below 1 μm, and except for kidney tissue, the indoor concentration and emission rate of these particle sizes were positively correlated with the power. The experimental results can provide data reference for the use of high-frequency electric knives in surgeries involving different human tissues in the operating room.

Residual impacts of a wildland urban interface fire on urban particulate matter and dust: a study from the Marshall Fire

The impacts of wildfires along the wildland urban interface (WUI) on atmospheric particulate concentrations and composition are an understudied source of air pollution exposure. To assess the residual impacts of the 2021 Marshall Fire (Colorado), a wildfire that predominantly burned homes and other human-made materials, on homes within the fire perimeter that escaped the fire, we performed a combination of fine particulate matter (PM2.5) filter sampling and chemical analysis, indoor dust collection and chemical analysis, community scale PurpleAir PM2.5 analysis, and indoor particle number concentration measurements. Following the fire, the chemical speciation of dust collected in smoke-affected homes in the burned zone showed elevated concentrations of the biomass burning marker levoglucosan (medianlevo = 4147 ng g−1), EPA priority toxic polycyclic aromatic hydrocarbons (median Σ16PAH = 1859.3 ng g−1), and metals (median Σ20Metals = 34.6 mg g−1) when compared to samples collected in homes outside of the burn zone 6 months after the fire. As indoor dust particles are often resuspended and can become airborne, the enhanced concentration of hazardous metals and organics within dust samples may pose a threat to human health. Indoor airborne particulate organic carbon (median = 1.91 μg m−3), particulate elemental carbon (median = .02 μg m−3), and quantified semi-volatile organic species in PM2.5 were found in concentrations comparable to ambient air in urban areas across the USA. Particle number and size distribution analysis at a heavily instrumented supersite home located immediately next to the burned area showed indoor particulates in low concentrations (below 10 μg m−3) across various sizes of PM (12 nm–20 μm), but were elevated by resuspension from human activity, including cleaning.Graphical

High time-resolution measurements of ultrafine and fine woodsmoke aerosol number and surface area concentrations in biomass burning kitchens: A case study in Western Kenya.

Indoor air pollution associated with biomass combustion for cooking remains a significant environmental health challenge in rural regions of sub-Saharan Africa; however, routine monitoring of woodsmoke aerosol concentrations continues to remain sparse. There is a paucity of field data on concentrations of combustion-generated ultrafine particles, which efficiently deposit in the human respiratory system, in such environments. Field measurements of ultrafine and fine woodsmoke aerosol (diameter range: 10-2500 nm) with field-portable diffusion chargers were conducted across nine wood-burning kitchens in Nandi County, Kenya. High time-resolution measurements (1Hz) revealed that indoor particle number (PN) and particle surface area (PSA) concentrations of ultrafine and fine woodsmoke aerosol are strongly temporally variant, reach exceedingly high levels (PN > 106 /cm3 ; PSA > 104 μm2 /cm3 ) that are seldom observed in non-biomass burning environments, are influenced by kitchen architectural features, and are moderately to poorly correlated with carbon monoxide concentrations. In five kitchens, PN concentrations remained above 105 /cm3 for more than half of the day due to frequent cooking episodes. Indoor/outdoor ratios of PN and PSA concentrations were greater than 10 in most kitchens and exceeded 100 in several kitchens. Notably, the use of metal chimneys significantly reduced indoor PN and PSA concentrations.

Indoor and Outdoor Particle Number Concentration in the Sapienza University Campus of Rome

Exposure to ultrafine particles has been associated with short- and long-term effects on human health. The object of this paper was to assess Particle Number Concentration (PNC) and size distribution in a university environment and study the indoor/outdoor relationships. Measurements were carried out using co-located (indoor/outdoor) condensation particle counters and size spectrometers during two seasonal periods characterized by different meteorological conditions at five selected classrooms different for size, capacity, floor and use destination. PNC was dominated by particles in the ultrafine mode both indoor and outdoor. The indoor/outdoor ratios were on average between 1 and 1.2 in the summer and between 0.6 and 0.9 in the winter. Mostly the differences found among classrooms could be related to the condition of use (i.e., crowding, natural air exchange, air conditioning, seasonality). Only little differences were found among PNC measured immediately outside the classrooms. Based on information taken during the measurement campaigns, on the classrooms condition of use, it was possible to assess as a source of indoor particles in the coarse mode, the presence of students and teachers.

Non-negative matrix factorization for the analysis of particle number concentrations: Characterization of the temporal variability of sources in indoor workplace

The temporal variability of indoor Particle Number (PN) concentrations, their determinants and their relative contributions in an occupied workspace were investigated. The presented study is based on the receptor modeling approach, focusing on Non-negative Matrix Factorization (NMF) to provide new insights on the source time variability. Continuous size distribution from 0.3 μm to 20 μm were collected with a short time step sampling (1 min) over six months in 2015. The measurements were made inside and outside an open-plan office occupied by 6–8 persons. NMF distinguished five major patterns obtained from PN concentrations time series. The apportionment results were expressed as source diurnal profiles and strengths by relating the obtained source contributions to the source information provided by the office occupancy and natural ventilation (the effect of opening windows). Factor 2 contributes to 75% of the total contributions for finer size fraction (<0.5 μm). Combining NMF results with indoor occupancy and windows states successfully demarcated the main sources of fluctuation. The diurnal profiles of the third factor (F3) and PN0.9−1.8 concentrations time series are very similar (r = 0.95). The diurnal variation of factor 1 is very similar to that observed for CO2 variations and PN6.25−12.5 time series. Coarse particles (>17.5 μm) are associated with the 4th factor. The latter does not contribute to any of the other particle ranges. The NMF factors interpretation was supported by correlation analysis and statistical tests, as well as by temporal variation comparison.

단독주택에서의 실내외 나노미세먼지 (UltraFine Particles) 동시측정을 통한 실내 UFP 분포특성과 호흡기관 침적율

단독주택에서의 실내외 나노미세먼지 (UltraFine Particles) 동시측정을 통한 실내 UFP 분포특성과 호흡기관 침적율

Effect of indoor and outdoor sources on indoor particle concentrations in South Korean residential buildings

The rising indoor air pollution from particles is a cause for concern especially in houses where children and the elderly reside. In South Korea, assessment of exposure to particle number (PN) in residential apartments, which account for 76% of all houses, is limited. In our study, the indoor and outdoor PN (sizes 0.3–10.0 µm) concentrations were measured in ten typical apartments for 24 h each. In addition, the occupants’ schedules were examined by conducting a survey.Results showed that the average outdoor PN concentrations were 0.30–4.37 × 109/m3 with very large deviations. Indoor peak events were mainly caused by cooking, and total emitted particles were 0.01–81.3 × 1013 particles. Indoor PN concentrations were sustained for a long time because of inefficient ventilation that led to lowered attenuation.Indoor particles are generated during various indoor activities. The daily-integrated particle exposures were 21.4% and 78.6% for indoor and outdoor sources, respectively. Thus, outdoor sources were the predominant sources of particle exposure compared with indoor sources. In conclusion, penetration from outdoor sources needs to be reduced by adding air filtration to improve the airtightness of buildings when introducing outdoor air to lower the indoor PN concentration.

Development and validation of an intra-calibration procedure for MiniDISCs measuring ultrafine particles in multi-spatial indoor environments

Since the real exposure to indoor ultrafine particles depends on temporal and spatial variation of aerosol concentration, particles dynamic behavior becomes relevant in studying indoor pollution. With this aim, the characterization of Ultrafine Particles (UFPs) variability within different environments (multi-spatial indoor environments) can be regarded as a specific tool in assessing the human exposure. In the case of urban indoor environments, instruments able to measure UFPs at high time resolution with high sensitivity are needed, lightweight and silent. For this purpose, personal monitors unipolar diffusion charging based could be used for their ease of use. Among them, Miniature DIffusion Size Classifier (MiniDISC), a small, silent and wearable analyzer measures particle number concentration, particle modal size and lung deposited surface area of nanoparticles at high time resolution, for dynamic or static use. Nevertheless, the typical ±30% accuracy specified by the manufacturer does not make this sensor reliable enough to measure gradients of urban doses of UFPs occurring in multi-spatial indoor environments.The presented work aims at improving the performances of MiniDISCs for their use in simultaneous measurement of urban UFPs by a multiple set-up, such as in indoor environments inside a building.For this purpose, a new intra-calibration procedure has been developed among MiniDISCs, named Best Intra-calibration (BIC), which corrects data of electrical signals of two or more instruments to those of one selected as reference. Compared to a linear regression analysis for PNC of UFPs, BIC procedure has two main advantages. First, it makes it possible to improve simultaneously the precision of particle number concentration (PNC) and particle modal size (PMS). Secondly, it allows multiple instruments to operate as a fleet, such as a spatial delocalization of an instrument in multiple environments.The procedure was tested in realistic environmental conditions, evaluating indoor PNC and PMS of UFPs by both parallel samplings and multi-spatial samplings. Three types of monitoring campaigns were carried out: inter-comparisons between PNC of UFPs from three MiniDISCs and one Condensation Particle Counter; intra-comparisons between PNC and PMS of UFPs from three MiniDISCs; urban monitoring in-field campaign of UFPs with three MiniDISCs in an indoor workplace, a physic laboratory, in the next hallway and outside. The latter campaign aimed at evaluating how UFPs are influenced by the interaction among different environments inside the building and by the work activity. For these purposes, the dynamical behavior and the ratios Indoor to Outdoor were investigated, in addition to a novel ratio Indoor to Hallway. The BIC procedure allows increasing the precision measured by the weighted coefficients of variation CVs of about 7 times. The results support the novel Intra-calibration procedure to improve the intra variability of MiniDISCs in parallel sampling, making them attractive for measuring UFPs by both the metrics PNC and PMS in multi-spatial indoor environments.

Performance characteristics of a fan filter unit (FFU) in mitigating particulate matter levels in a naturally ventilated classroom during haze conditions.

The performance of a low-cost fan filter unit (FFU) in mitigating hazardous particulate matter (PM) levels in a naturally ventilated school classroom is presented. The FFU can be considered as a simplified mechanical ventilation and air-conditioning system without heating and cooling functions. The FFU improves indoor air quality through introduction of cleaned outdoor air to flush out internally generated heat and moisture and reducing infiltration by maintaining indoor pressurization. Indoor particle number concentrations were reduced between 85% and 95%. The particle removal performance (PRFFFU ) of the FFU is determined and incorporated into the augmented façade penetration factor (Paug ). A case-specific recursive dynamic mass balance model is used to characterize the infiltration factor (FINF ), deposition rate (K), and the penetration efficiency (Paug ) from continuously monitored indoor and outdoor mass concentration levels. Computed "Paug " (0.07, 0.09, and 0.13) and "FINF " (0.06, 0.08, and 0.11), respectively, for PM10, PM2.5, and PM1 suggest that exposure to PM was significantly reduced indoors. The effectiveness of the FFU for reduced "FINF " and "Paug " may be attributed to its superior filtration, dilution, and exfiltration mechanisms. In comparison with alternative PM mitigation solutions, the FFU is effective, affordable, and sustainable.

Predictors of Indoor-Outdoor Ratio of Particle Number Concentrations in Israel

Background: Trends of indoor-outdoor ratios (IOR) of particle number concentrations (PNC) by temporal and meteorological factors can enhance our understanding of this harmful exposure and its sources.Methods: PNC data was collected from a one-year field campaign where simultaneous meteorological parameters were measured continuously usind Dylos DC500 devices in five locations in Israel, which is one of the high PM area. Generalized linear models were used for estimating the association between the explanatory variables (outdoor PNC, hour of the day, weekend/workday, season, ambient temperature, ambient relative humidity, wind speed) and the IOR.Results: The median is 0.830 for fine IOR and is 0.702 for coarse IOR in general, and all IOR medians were ≤1 in entire locations. Lower IORs were experienced at night, with the daily peak in IOR around noon. The IORs shows a double-hump pattern with higher IOR in spring and autumn, and lower IOR in summer and winter.Conclusions: The outdoor PNC was found to be the most important predictor of indoor PNC at any meteorological conditions, especially for fine particles, but the residents’ preferences and activities may dominate the IOR when considerable indoor emissions prevail whereas smoking and cooking tend to elevate the fine PNC, house holding activities effect to a larger extent the coarse fraction.

Predictors of the Indoor-to-Outdoor Ratio of Particle Number Concentrations in Israel

Exposure to airborne particles is a risk factor of many short- and long-term health effects. Most epidemiological studies include estimates of exposure to ambient particles, however, people living in developed countries spend most of their time indoors. This work presents an analysis of a field campaign of simultaneous measurements of indoor-to-outdoor particle number concentrations (PNCs) in Israel. Fine and coarse PNCs were continuously measured using Dylos DC1700 devices from October 2016 to October 2017. The median outdoor PNC was always higher than the indoor PNC in all the five sampling locations. Outdoor fine PNCs peak during the night and experience a trough in the afternoon. The median of the fine indoor-to-outdoor PNC ratio (IOR) was 0.83, with an inter quartile range (IQR) of 0.59. The median of the coarse IOR was 0.70, with an IQR of 0.77. Lower IORs were experienced at night than during the day, with a daily peak (IOR &gt; 1) around noon. Information about the IOR in different regions and seasons may help epidemiologists and policy makers understand the true health effects of particulate air pollution, and correct their exposure estimations such that they account for indoor exposure as well.

Impacts of Aviation Emissions on Near-Airport Residential Air Quality.

Impacts of aviation emissions on air quality in and around residences near airports remain underexamined. We measured gases (CO, CO2, NO, and NO2) and particles (black carbon, particle-bound aromatic hydrocarbons, fine particulate matter (PM2.5), and ultrafine particles (reported using particle number concentrations (PNC) as a proxy)) continuously for 1 month at a residence near the Logan International Airport, Boston. The residence was located under a flight trajectory of the most utilized runway configuration. We found that when the residence was downwind of the airport, the concentrations of all gaseous and particulate pollutants (except PM2.5) were 1.1- to 4.8-fold higher than when the residence was not downwind of the airport. Controlling for runway usage and meteorology, the impacts were highest during overhead landing operations: average PNC was 7.5-fold higher from overhead landings versus takeoffs on the closest runway. Infiltration of aviation-origin emissions resulted in indoor PNC that were comparable to ambient concentrations measured locally on roadways and near highways. In addition, ambient NO2 concentrations at the residence exceeded those measured at regulatory monitoring sites in the area including near-road monitors. Our results highlight the need for further characterization of outdoor and indoor impacts of aviation emissions at the neighborhood scale to more accurately estimate residential exposures.

Global Alliance against Chronic Respiratory Diseases demonstration project: aerosol pollution and its seasonal peculiarities in primary schools of Vilnius.

BackgroundThe growing public health concern caused by non-communicable diseases in urban surroundings cannot be solved by health care alone; therefore a multidisciplinary approach is mandatory. This study aimed to evaluate the airborne aerosol pollution level in primary schools as possible factor influencing origin and course of the diseases in children.MethodsSeasonal aerosol particle number concentration (PNC) and mass concentration (PMC) were studied in the randomly selected eleven primary schools in the Lithuanian capital, Vilnius, as model of a middle-size Eastern European city. Total PNC in the size range from 0.01 to >1.0 μm in diameter was measured using a condensation particle counter. Using an optical particle sizer, PNC was measured and PMC estimated for particles from 0.3 to 10.0 μm. A descriptive statistics was used to estimate the aerosol pollution levels.ResultsDuring all seasons, local cafeterias in the absence of ventilation were the main sources of the elevated levels of indoor PMC and PNC (up to 97,500 particles/cm3). The other sources of airborne particulates were the children's activity during the lesson breaks with PMC up to 586 μg/m3. Soft furniture, carpets in the classrooms and corridors were responsible for PMC up to 200 μg/m3. Outdoor aerosol pollution (up to 18,170 particles/cm3) was higher for schools in city center. Elevated air pollution in classrooms also resulted from intermittent sources, such as construction work during classes (200–1000 μg/m3) and petrol-powered lawn trimmers (up to 66,400 particles/cm3).ConclusionThe results of our survey show that even in a relatively low polluted region of Eastern Europe there are big differences in aerosol pollution within middle-sized city. Additional efforts are needed to improve air quality in schools: more frequent wet cleaning, monitoring the operation of ventilation systems, a ban on construction works during school year, on a use of sandblasting mechanisms in the neighborhood of schools.

A field indoor air measurement of SARS-CoV-2 in the patient rooms of the largest hospital in Iran

The coronavirus disease 2019 (COVID-19) emerged in Wuhan city, China, in late 2019 and has rapidly spread throughout the world. The major route of transmission of SARS-CoV-2 is in contention, with the airborne route a likely transmission pathway for carrying the virus within indoor environments. Until now, there has been no evidence for detection of airborne severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and this may have implication for the potential spread of the COVID-19. We investigated the air of patient rooms with confirmed COVID-19 in the largest hospital in Iran, on March 17, 2020. To collect the SARS-CoV-2 particles, ten air samples were collected into the sterile standard midget impingers containing 20 mL DMEM with 100 μg/mL streptomycin, 100 U/mL penicillin and 1% antifoam reagent for 1 h. Besides, indoor particle number concentrations, CO2, relative humidity and temperature were recorded throughout the sampling duration. Viral RNA was extracted from samples taken from the impingers and Reverse-Transcription PCR (RT-PCR) was applied to confirm the positivity of collected samples based on the virus genome sequence. Fortunately, in this study all air samples which were collected 2 to 5 m from the patients' beds with confirmed COVID-19 were negative. Despite we indicated that all air samples were negative, however, we suggest further in vivo experiments should be conducted using actual patient cough, sneeze and breath aerosols in order to show the possibility of generation of the airborne size carrier aerosols and the viability fraction of the embedded virus in those carrier aerosols.

The trace of airborne particulate matter from smoking e-cigarette, tobacco heating system, conventional and hand-rolled cigarettes in a residential environment

Indoor particle number concentrations and size distributions were monitored in a typical, residential living room, considering two independent variables: smoking activities (using e-cigarettes, tobacco heating systems (THS), conventional and hand-rolled cigarettes) and the operation of the air conditioning (AC) system. Each smoking device exhibited its own characteristic size distribution (its own “trace”), in the room atmosphere, which was also affected by the AC operation. All devices emitted ultrafine and fine particles especially in the range around 100 nm. The minimum average PM number or mass concentrations in any size were observed for the THS (either with the AC on or off). The PM1 number concentrations were maximum when conventional cigarettes were smoked, especially when the AC was off. In the case of the coarse particles, the PM(1–10) number concentrations were maximum when hand-rolled cigarettes were smoked (and AC was on). When the AC was off, the maximum PM(1–10) number concentration was recorded when the e-cigarette was used. The effect of the AC on particle number concentrations depended on their size and their origin. A factorial ANOVA corroborated that the two independent variables affected significantly (at p < 0.05) the airborne PM number concentrations. Specifically, low versus high air temperature, fan operation or not, affected differently particles in different size ranges and for different smoking activities.

Ultrafine particle emission and its potential health risk from residential solid fuel combustion

Residential solid fuel combustion for domestic heating and cooking is an important source for ambient and indoor air pollution. It produces large amount of PM2.5 during the combustion process and introduce significant health risk to indoor personal. Recently many studies have indicated that ultrafine particles (PM0.1) contribute to majority of particle number concentration of the emitted PM2.5 from residential solid fuel combustion. However, the emission of ultrafine particles and their potential health impact are not drawing much attention since investigations on their emission and health risk assessment are usually merged into PM2.5 mass concentration based evaluations. Therefore, ultrafine particle emission from residential solid fuel combustion, as well as their potential health impact, may be overlooked in current PM emission control and management. This review summarizes the current research processes reported in literatures on ultrafine particle emission from residential solid fuel combustion, including their formation mechanism, emission characteristics, as well as the potential health impact from the related indoor ultrafine particle exposures. First of all, it can be concluded that ultrafine particles are mostly formed via chemical reaction, homogeneous nucleation, and heterogeneous nucleation of organic and inorganic vapors released during combustion processes due to the low combustion temperature and efficiency. The formed ultrafine particles will sequentially grow into larger particles via heterogeneous nucleation, coagulation and sintering. Meanwhile, as reported in most of the literatures, both laboratory combustion platform studies and indoor air monitoring studies have indicated that ultrafine particle emission is generally occurred during residential solid fuel combustion in regardless of fuel and stove types used as well as combustion modes. These ultrafine particles account for the majority of particle number concentration. In real residential households, ultrafine particles emitted from residential solid fuel combustion will elevate the indoor particle number concentration, which eventually introduce significant health risk to indoor personal. Although there are still debates on the general associations between ultrafine particles and certain health effects, it is clear that health effect induced by exposure to ultrafine particles should be carefully considered at least in residential solid fuel combustion aspect. Finally, the current issue of using PM2.5 mass concentration as evaluation parameter without considering number concentration of ultrafine particle is discussed. Since PM2.5 mass concentration is mostly dominated by larger particles, it may not effectively represent the characteristics of ultrafine particle emission as well as their health impact. Therefore, it seems that merging ultrafine particles into PM2.5 mass concentration will significantly overlook ultrafine particle emission and their health impact in residential solid fuel combustion. From PM emission control aspect, it can be concluded that although the current strategies based on PM2.5 emission control (i.e. using “cleaner” fuels and/or more advanced stoves) have significantly promoted the reduction of PM2.5 mass concentration, they may not be effective in controlling ultrafine particle number concentration emitted from residential solid fuel combustion. Therefore, we suggest that control and management procedures on ultrafine particles should also be considered (i.e. from particle number concentration aspect) in addition to the current PM2.5 mass concentration emission control and management in residential solid fuel combustion.

Fine and ultrafine particles concentrations in vape shops

Vape shops are widespread due to the popularity of electronic cigarettes (e-cigs) as an alternative to tobacco cigarettes. In this study, sixty-seven Southern California vape shops were randomly surveyed for building characteristics, ventilation, and business patterns. Based on the survey results, six representative shops were recruited for real-time measurements of indoor and outdoor fine and ultrafine particles concentrations on a busy and less busy day. Occupancy, vaping frequency, and opening and closing of doors were recorded, and shop air exchange rate was determined. Indoor CO2, relative humidity, and temperature were also recorded. In addition, simultaneous measurements were taken at increasing distances away from a vaping area to assess the mixing and spatial profiles of particle levels inside the shops. During active vaping, real-time indoor particle number concentration and gravimetric-corrected PM2.5 mass concentration across the six vape shops varied from 1.3 × 104 to 4.8 × 105 particles/cm3 and from 15.5 to 37,500 μg/m3, respectively. The spatial profiles of particle number and mass were more uniformly mixed than expected in an indoor environment. Total vaping frequency was the main predictor of particle concentrations inside the vape shops when indoor-outdoor particle mass transfer is minimal (doors closed).

Characteristics of Indoor PM2.5 Concentration in Gers Using Coal Stoves in Ulaanbaatar, Mongolia.

Coal combustion in ger areas is the main source of ambient air pollution in Ulaanbaatar (Mongolia). This study determined the characteristics of indoor PM2.5 concentrations in gers using coal stoves during winter. The study population consisted of 60 gers in the Chingeltei district of Ulaanbaatar. The indoor particle number concentration (PNC) in each ger was measured using a Dylos DC1700 particle counter for 24 h in January and February 2016. The PNC by Dylos was converted into the mass concentration using a calibration equation developed using a collocated real-time light scattering monitor adjusted by gravimetric measurement. The average 24 h PM2.5 concentration was 203.9 ± 195.1 μg/m3 in gers with traditional stoves (n = 29) and 257.5 ± 204.4 μg/m3 in those with improved stoves (n = 31). In the daily profile, concentrations were lower at night, increased in the early morning, and peaked up to noon. The temperature in gers was slightly higher than that recommended in winter. Many development-assistance programs have supported the installation of improved energy-efficient stoves. Better control measures are needed to improve the indoor air quality of gers.

Exposure to air particulate matter with a case study in Guangzhou: Is indoor environment a safe haven in China?

Urban residents spend the majority of time in indoor environments, which, however, may not be a safe haven for staying away from outdoor air pollution, especially in China. To examine this hypothesis, the particle mass concentrations (0.056–18 μm) and number concentrations (14–660 nm) were simultaneously measured in and outside of three typical urban indoor settings (n = 9), i.e., school, office and residence in Guangzhou, China from October–November 2014 (dry weather season) and June–August 2015 (wet weather season). The indoor and outdoor particle number concentrations were positively correlated with each other at all three sampling settings for both dry and wet weather seasons (r2 = 0.13–0.65, p < 0.001). The infiltration factors and indoor/outdoor ratios of particles (14–660 nm) were estimated at 0.30–0.75 and 0.85–1.5, respectively, which were comparable to or higher than those (0.12–0.76 and 0.03–1.1) found in cites of other countries under infiltration conditions. Furthermore, the average infiltration factor of fine particle numbers (50–660 nm) in an office was 0.61 during a severe haze episode, indicating that approximately 60% of outdoor particles penetrated indoors. All findings suggested an efficient transport of outdoor particle sources into indoor environment, confirming that exposure of the general public to indoor particles in China should not be overlooked due to effective infiltration of outdoor particles and frequent heavy haze episodes.

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.