Indoor Air Particles Research Articles

Nonthermal plasma air disinfection for the inactivation of airborne microorganisms in an experimental chamber and indoor air.

Airborne transmission of diseases presents a serious threat to human health, so effective air disinfection technology to eliminate microorganisms in indoor air is very important. This study evaluated the effectiveness of a non-thermal plasma (NTP) air disinfector in both laboratory experiments and real environments. An experimental chamber was artificially polluted with a bioaerosol containing bacteria or viruses. Additionally, classroom environments with and without people present were used in field tests. Airborne microbial and particle concentrations were quantified. A 3.0 log10 reduction in the initial load was achieved when a virus-containing aerosol was disinfected for 60min and a bacteria-containing aerosol was disinfected for 90min. In the field test, when no people were present in the room, NTP disinfection decreased the airborne microbial and particle concentrations (P<0.05). When people were present in the room, their constant activity continuously contaminated the indoor air, but all airborne indicators decreased (P<0.05) except for planktonic bacteria (P=0.094). NTP effectively inactivated microorganisms and particles in indoor air.

Multi-pathway exposure assessment of organophosphate flame retardants in a southern Chinese population: Main route identification with compound-specificity

In this study, we conducted comprehensive organophosphorus flame retardant (PFR) exposure assessments of both dietary and non-dietary pathways in a rural population in southern China. Skin wipes were collected from 30 volunteers. Indoor and outdoor air (gas and particles), dust in the houses of these volunteers, and foodstuffs consumed by these volunteers were simultaneously collected. The total PFR concentrations in dust, gas, and PM2.5 varied from 53.8 to 5.14 × 105 ng/g, 0.528 to 4.27 ng/m3, and 0.390 to 16.5 ng/m3, respectively. The forehead (median of 1.36 × 103 ng/m2) and hand (median of 920 ng/m2) exhibited relatively high PFR concentrations, followed by the forearm (median of 440 ng/m2) and upper arm (median of 230 ng/m2). The PFR concentrations in the food samples varied from 0.0700 to 10.9 ng/g wet weight in the order of egg > roast duck/goose and vegetable > pork > chicken > fish. Tris(1-chloro-isopropyl) phosphate (TCPP) was the main PFR in the non-diet samples, whereas the profiles of PFR individuals varied by food type. Among the multiple pathways investigated (inhalation, dermal exposure, dust ingestion, and food ingestion), dermal absorption and dust ingestion were the predominant pathways for tris(2-chloroethyl) phosphate (TCEP) and bisphenol A-bis(diphenyl phosphate) (BDP), respectively, whereas dietary exposure was the most important route for other chemicals.

Lung-depositing surface area (LDSA) of particles in office spaces around Europe: Size distributions, I/O-ratios and infiltration

Air pollution, and specifically particulate matter pollution, is one of the greatest dangers to human health. Outdoor air pollution ranks third in causes for premature death. Improving indoor air quality is of immense importance, as the time spent indoors is often much greater than the time spent outdoors. In this experimental study, we evaluate the levels of particle pollution in indoor air in four offices across Europe, compare the indoor particles to outdoor particles and assess where the particles originate from. The measurements were conducted with an Electrical Low-Pressure Impactor (ELPI+) for particles between 6 nm and 1 μm. The chosen metric, lung-deposited particle surface area (LDSA), targets the health impacts of particle pollution. Based on the measurements, we determined that most of the indoor air particles infiltrated from outdoor air, although two of the offices had very limited indoor activity during the measurement campaigns and may not represent typical use. The highest median indoor LDSA concentration during daytime hours was 27.2 μm2/cm3, whereas the lowest was 2.8 μm2/cm3. Indoor air in general had lower LDSA concentrations than outdoor air, the corresponding outdoor LDSA concentrations being 35.8 μm2/cm3 and 9.8 μm2/cm3. The particle size ranges which contributed to the highest concentrations were 50–100 nm and 300–500 nm. These size ranges correspond to soot mode and accumulation mode particles, which represent local and regional sources, respectively. Based on this study, limiting particle infiltration is the key factor in keeping indoor air in offices free of lung-depositing particles.

Functionalized zinc oxide nanorods – polypropylene nonwoven composite with high biological and photocatalytic activity

This work presents a comprehensive approach to elaborating new active polypropylene-zinc oxide composite material with a well-developed specific surface area. Fibrous polypropylene material, made via the melt-blown technique, plays a role of a high-porosity substrate for modification. The hydrothermal chemical bath deposition (CBD) method adjustment is suited to cover its surface with various ZnO nanorods (NRs). Due to the CBD method, it is possible to control the structures of obtained ZnO via the concentration of reagents used in the synthesis. The material analysis allows for determining the crystal form of ZnO, the fiber coverage degree, and the effectiveness of the surface activation process. The investigation also confirmed the bactericidal (differences in microorganism survivability exposed on PP-ZnO material ranged from approx. 50–0%) and photocatalytic (increase in MB decomposition rate constant value from 0.0374 to 0.173 h-1) properties of the developed PP-ZnO composite materials. Aerosol and bioaerosol particles in indoor air may be dangerous, especially for human health, since ventilation and air-conditioning systems create excellent conditions for growing microorganisms. For this reason, an exemplary application of the proposed material is the separation processes. Investigations into the filtration process for solid KCl particles and DEHS droplets (diameters from 20 nm to 2 µm) showed that modified nonwovens maintain their original (before modification) airflow resistance and exhibit increased effectiveness for particles larger than 200 nm (differences in the QF value in the range of 0.001–0.004).

Long-term application of low-cost sensors for monitoring indoor air quality and particle dynamics in a commercial building

Human exposure to indoor particles has been associated with increased rates of morbidity and mortality. To develop efficient particle control measures in indoor environments, there has been an increasing demand for the use of low-cost particle sensors towards indoor air quality applications. However, few studies have examined the potential application of low-cost particle sensors for monitoring indoor air quality and particle dynamics under a long-term deployment in commercial buildings. Given this background, we conducted a case study of six-month field investigation on the use of low-cost sensors for evaluating particle emission, concentration, and removal in an office building. Our results illustrate the necessity of improving control strategies for fine particles <1 μm in commercial buildings (e.g., utilizing high efficiency particle filters). Deploying low-cost particle sensors within an air handling unit and occupied spaces could be a quick and simple approach for monitoring particle filtration effectiveness of a mechanical ventilation system. Furthermore, this study suggests that coupling low-cost particle sensors with CO2 measurements can offer informative data for analyzing particle emissions associated with occupant activities. Our results reveal that particle resuspension due to occupants can be an important emission source for particles >5 μm in office environments. The study findings could help future research and applications of low-cost sensors in monitoring indoor air quality in commercial buildings.

Occurrence of liquid crystal monomers in indoor and outdoor air particle matters (PM10): Implications for human exposure indoors

Liquid crystal monomers (LCMs) are potentially persistent, bioaccumulating, and toxic substances. However, limited data are available on the occurrence of LCMs in indoor and outdoor air particle matter (PM10) in residential areas. Herein, residential areas near an e-waste dismantling center (Guiyu Town, Shantou City), as well as areas away from the e-waste site (Jiedong District, Jieyang City) were selected as the sampling areas. PM10 was collected from the indoor environments of Guiyu (IGY) and Jieyang (IJY), as well as those from the outdoor environments (OGY and OJY) using the high-volume air samplers (TH-10000C). The levels of 57 LCMs in PM10 were analyzed, and the highest concentrations of LCMs were found in IGY (0.970–1080 pg/m3), followed by IJY (2.853–455 pg/m3), OGY (0.544–116 pg/m3) and OJY (0.258–35.8 pg/m3). No significant difference was observed for LCM levels in indoor PM10 between the two areas (p > 0.05), which were significantly higher than those in outdoors (p < 0.05), indicating that the release of electronic products in general indoor environments is a source of LCMs that cannot be ignored. The compositions of LCMs in outdoors were not consistent with those of indoors. The correlation analysis of individual LCMs suggested potential different sources to the LCMs in indoor and outdoor environments. The median daily intake values of Σ46LCMs via inhalation were estimated as 0.440, 1.46 × 10−2, 0.170 and 1.19 × 10−2 ng/kg BW/day for adults, and as 2.27, 2.60 × 10−2, 0.880 and 2.10 × 10−2 ng/kg BW/day for toddlers, respectively, indicating much higher exposure doses of LCMs indoors compared with the outdoors, and much higher doses for toddlers compared with adults (p < 0.05). These results reveal the potentially adverse effects of LCMs on vulnerable populations, such as toddlers, in indoor environments.

Effects of Ionization on the Filtration of Fine and Ultrafine Particles in Indoor Air

As we spend approximately 80% of our time indoors, improving indoor air quality is necessary to lessen the spread and impacts of respiratory diseases and other health issues caused by particle pollution. Currently, in many countries, the primary method of cleaning indoor air is by using better, higher-grade filters in a recirculating air system or increasing ventilation with outdoor air. One way to supplement these time-tested approaches is by implementing ionization. We used a bipolar ionizer to test the removal efficiency of filters on different particle sizes with and without ionization. Calibrated cigarettes were used to generate smoke into a 28-cubic-meter chamber with a recirculating air handling system. It was found that ionization had a 275% increase in the removal efficiency of the most penetrating particle sizes (100-500 nm). We conclude that ionization drastically improves the filter removal efficiency of fine and ultrafine particles in indoor environments.

Identifying the contributions of root and foliage gaseous/particle uptakes to indoor plants for phthalates, OPFRs and PAHs

Understanding the uptake pathways of organic chemicals in plants can help us use plants as biosentinels for human exposure, and as remediation tools for contaminated sites. Herein, we investigated the relative contributions of root and foliar (gas and particle) uptake pathways to indoor ornamental plants for phthalates (PAEs), organophosphorus flame retardants (OPFRs), and polycyclic aromatic hydrocarbons (PAHs). We looked at different kinds of indoor ornamental plants via pot and hydroponic control experiments, comparing the levels between their leaves and indoor air gaseous and particle phases, floor dust, and window film. Contributions of soil and foliage uptakes were calculated based on chemical concentrations in leaves of hydroponic and soil cultured plants and their mass uptake rates. Across all compounds, the contributions of root uptake to the chemicals in soil cultured plants ranged from 47.5 % to 88.5 %. We used binary first-order mass conservation equations to calculate the contributions of foliage uptake via gaseous and particle phases to the chemicals with similar Kow in plant leaves. Foliar uptake of PAEs occurred mainly via particle adsorption, for light PAHs via gaseous absorption, and for OPFRs via both particle and gaseous uptakes. Negative correlations between chemicals' foliage uptake ratios and their Kow and Koa values suggest that foliage uptake may be influenced by both chemical hydrophilicity and lipophilicity.

Investigating the associations between organophosphate flame retardants (OPFRs) and fine particles in paired indoor and outdoor air: A probabilistic prediction model for deriving OPFRs in indoor environments

Contaminants of emerging concern such as organophosphate flame retardants (OPFRs) are associated with atmospheric fine particles (PM2.5), which pose the greatest health risk in the world. However, few surveys have explored the interaction between PM2.5 and OPFRs in residential paired indoor/outdoor environments. 11 priority OPFRs and PM2.5 were investigated across 178 paired indoor and outdoor air samples taken from 89 children’s households in southern Taiwan, across cold and warm seasons. This involved exploring their associations with building characteristics, interior materials, and human activities. We developed a probabilistic predictive model for indoor OPFRs based on the indoor/outdoor (I/O) ratio of contaminants and an air quality index. The significant associations of paired indoor/outdoor OPFRs and PM2.5 were explored. The indoor level of OPFRs was greater than that of outdoor households, contrasting with PM2.5. The I/O OPFRs ratio was higher than 1 (except for TEHP, EHDPP, and TCP), which suggests that the sources of OPFRs were primarily emitted from indoors. Indoor TCEP was significantly positively associated with indoor and outdoor PM2.5. The OPFR level detected in apartments was higher than in houses due to the greater decoration, furniture and electronic devices. However, this was not the case for PM2.5. TCIPP was the dominant compound in paired indoor and outdoor air. The indoor OPFR predictive model obtained a high accuracy with an R2 value of 0.87. The material used in mattresses, the use of purifiers and heaters, and the total material area were the main influencing factors for indoor OPFRs in households. These findings could provide important evidence of the interaction between paired indoor/outdoor OPFRs and PM2.5 and interior equipment in different building types. In addition, it could prevent the potential risks posed by indoor/outdoor air pollutants and eliminate OPFR emissions through the selection of better construction and building materials.

Mathematical Model of the Pulse Generation of Decontaminating Aerosols.

A mathematical model of the pulse generation of decontaminating aerosols utilizing the energy of high-energy materials (HEM) is proposed with account for the physical and chemical properties of the atomized substance, HEM characteristics, and gas generator parameters. Such a model is needed to counter the environmental hazards, process emissions, and terrorist attacks with hazardous and dangerous aerosols. Another aspect of the problem is the danger of biological aerosols carrying viral or microbial particles that are spread naturally or induced using biological weapons. In many cases, the mission is not only to neutralize aerosol particles in indoor air and on surfaces but also to do it quickly. In this regard, an attractive option is the pulse method for generating special aerosols aimed at quickly, within a few seconds, creating a cloud of particles that will interact with hazardous aerosol particles and decontaminate them. HEM energy is proposed to be used for the pulse generation of such aerosols. It is important not only to atomize the decontaminating aerosol quickly and evenly in space but also to preserve the useful physical and chemical properties of the particles. To test the regimes and methods of pulse generation, an adequate mathematical model of the process is required, which is proposed in this manuscript.

Indoor air particles in research vessel from Shanghai to Antarctic: Characteristics, influencing factors, and potential controlling pathway

Despite millions of seafarers and passengers staying on ships each year, few studies have been conducted on the indoor air quality inside ship hulls. In this study, we investigated the levels and size distribution of indoor particulate matter during two cruises of the research vessel “Xuelong” from Shanghai to Antarctica. The results showed that the particle size less than 2.5 µm (PM2.5), and particle size less than 10 µm (PM10) concentrations in different rooms of the ship widely varied. We observed high particulate matter (PM) levels in some of the rooms. The mass concentration distribution was dominated by 1–4 µm particles, which may have been caused by the hygroscopic growth of fine particles. The dominant factors influencing PM concentrations were indoor temperature, relative humidity, and human activity. We quantified contributions of these factors to the levels of indoor particles using a generalized additive model. In clean rooms, the levels of indoor particles were controlled by temperature and relative humidity, whereas in polluted rooms, the levels of indoor particles were mainly influenced by temperature and human activity, which implied that controlling temperature and human activity would efficiently reduce the levels of indoor particles.

Effect of Different Ventilation Systems on Concentrations of Indoor Particle Emitted from Floor of the Office

A three-dimensional numerical simulation of airflow, temperature, and pollutant concentration distributions with underfloor air distribution (UFAD) system and displacement ventilation (DV) systems are presented for different operating conditions. Since the particles deposited on the floors can be re-introduced into the air through re- suspension and then constitute a threat to human’s health, an optimal ventilation system is required to reduce the indoor air particle concentrations. In the present study, the effects of different systems on the concentrations of indoor particles are numerically investigated by an Eulerian-Lagrangian method, and the RNG k-ε model is adopted for the simulation. Three different supply air velocities (0.2-0.4 m/s) and different supply air temperatures (20 ℃, 22 ℃ and 24 ℃) are considered in the simulation. Meanwhile, the thermal effect of the human body on the micro-environment and its interaction with the surrounding environment are comprehensively evaluated. The simulation results shows that for the UFAD and DV systems, good performance of particle removal is obtained with the high air supply speed for the DV system, while under larger temperature gradient of the indoor environment, the UFAD system is capable of reducing the concentration of the particles emitted from the floors with lower air supply speed.

A Quantitative Risk Estimation Platform for Indoor Aerosol Transmission of COVID-19.

Aerosol transmission has played a significant role in the transmission of COVID‐19 disease worldwide. We developed a COVID‐19 aerosol transmission risk estimation model to better understand how key parameters associated with indoor spaces and infector emissions affect inhaled deposited dose of aerosol particles that convey the SARS‐CoV‐2 virus. The model calculates the concentration of size‐resolved, virus‐laden aerosol particles in well‐mixed indoor air challenged by emissions from an index case(s). The model uses a mechanistic approach, accounting for particle emission dynamics, particle deposition to indoor surfaces, ventilation rate, and single‐zone filtration. The novelty of this model relates to the concept of “inhaled & deposited dose” in the respiratory system of receptors linked to a dose–response curve for human coronavirus HCoV‐229E. We estimated the volume of inhaled & deposited dose of particles in the 0.5–4 μm range expressed in picoliters (pL) in a well‐documented COVID‐19 outbreak in restaurant X in Guangzhou China. We anchored the attack rate with the dose–response curve of HCoV‐229E which provides a preliminary estimate of the average SARS‐CoV‐2 dose per person, expressed in plaque forming units (PFUs). For a reasonable emission scenario, we estimate approximately three PFU per pL deposited, yielding roughly 10 PFUs deposited in the respiratory system of those infected in restaurant X. To explore the model's utility, we tested it with four COVID‐19 outbreaks. The risk estimates from the model fit reasonably well with the reported number of confirmed cases given available metadata from the outbreaks and uncertainties associated with model assumptions.

On the Water-Soluble Organic Matter in Inhalable Air Particles: Why Should Outdoor Experience Motivate Indoor Studies?

The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited knowledge on indoor OA, and particularly on its water-soluble organic matter (WSOM) fraction is the basis of this feature paper. Inspired by studies on outdoor OA, this paper discusses and prioritizes issues related to indoor water-soluble OA and their effects on human health, providing a basis for future research in the field. The following three main topics are addressed: (1) what is known about the origin, mass contribution, and health effects of WSOM in outdoor air particles; (2) the current state-of-the-art on the WSOM in indoor air particles, the main challenges and opportunities for its chemical characterization and cytotoxicity evaluation; and (3) why the aerosol WSOM should be considered in future indoor air quality studies. While challenging, studies on the WSOM fraction in air particles are highly necessary to fully understand its origin, fate, toxicity, and long-term risks indoors.

Office Indoor PM and BC Level in Lithuania: The Role of a Long-Range Smoke Transport Event

While the impacts of climate change on wildfires and resulting air pollution levels have been observed, little is known about how indoor air filtering systems are performing under intensive smoke conditions. For this aim, particle number size distribution and concentration in a size range 0.5–18 µm and equivalent black carbon (eBC) mass concentration were measured in a modern office with a mechanical ventilation system. Measurements took place from 30 September to 6 October 2020 in the Center for Physical Sciences and Technology (FTMC) campus located in the urban background environment in Lithuania. During the measurement campaign, an intensive pollution episode, related to long-range transport wildfire smoke, was observed. The results indicated that the smoke event increased both indoor and outdoor eBC mass concentrations twice. Filters were non-selective for different eBC sources (biomass burning versus traffic) or chemical composition of carbonaceous aerosol particles (eBC versus brown carbon (BrC)). Air filtering efficiency was found to be highly dependent on particle size. During the smoke event the highest particle number concentration was observed at 2.1 µm and 1.0 µm size particles in outdoor and indoor air, respectively. Differences of indoor to outdoor ratio between event and non-event days were not significant. Because of lower removal rate for small particles, eBC had higher contribution to total PM2.5 mass concentration in indoor air than in outdoor air. The results gained are crucial for decision-making bodies in order to implement higher-quality air-filtering systems in office buildings and, as a result, minimize potential health impacts.

Relationship between Indoor High Frequency Size Distribution of Ultrafine Particles and Their Metrics in a University Site

Exposure to ultrafine particles (UFPs size &lt; 100 nm) in life and work environments can contribute to adverse health effects also in terms of health burden of related diseases over time. The choice of parameters which better characterize UFPs is challenging, due to their physical-chemical properties and their variable size. It is also strictly related to the availability of different instrumental techniques. In the present study we focus on real time high frequency (1 Hz) UFPs particle size distribution (PSD) and their relationship with total particle number concentration (TPNC) and mean particle diameter (Davg) as a contribution characterizing by size the human exposure to UFPs in an indoor site of the University of Rome “Sapienza” (Italy). Further considerations about UFPs contribution to nucleation mode (NM) and accumulation mode (AM) have been highlighted, also in order to investigate the contribution of polycyclic aromatic hydrocarbons (PAHs) surface-adsorbed on indoor air particles (pPAHs). High indoor TPNC values were registered during the rush hours (early morning and mid/late afternoon) according to the outdoor influences originated from anthropogenic activities. AM mainly contribute to the indoor TPNC during working days showing high correlation with pPAHs. These findings may provide useful indications in terms of occupational exposure to UFPs since there are many evidences that indoor exposures to such pollutants may be associated with adverse health effects also in working environments.

Development of screening criteria for microplastic particles in air and atmospheric deposition: critical review and applicability towards assessing human exposure

Over the last several years there has been an increase in studies reporting the presence of microplastic particles (MPs) in both indoor and outdoor air. Data reported reflect a variety of different types of air samples, which have helped to demonstrate the ubiquity of MPs in the atmosphere and their potential contribution to atmospheric particulate matter (PM). The relative quality of the data reporting on MPs in air has not been evaluated, but represents an important step towards improving our overall understanding of the human health implications in relation to inhalation exposure to MPs. Adopting recent approaches that have been proposed to assess the quality of data for those studies reporting concentrations in biota and water samples, we identify a suite of criteria used to screen studies reporting MPs in air for the purposes of evaluating their usefulness in assessing human exposure. Here we review and summarize data from 27 studies reporting MPs in various types of air samples and evaluate each of the studies against 11 separate criteria representing four main categories (sampling; contamination mitigation; sample purification / handling; characterization and application towards assessing human exposure). On average, studies scored 48.6% (range 18.2–81.8%) of the maximum score. Only one study received a positive score for all criteria, implying that there remains a need for future studies to consider strengthening implementation and reporting of QA/QC protocol. The most urgent areas requiring attention relate to the need for studies to avoid and verify background contamination and to strengthen the quantification of method recovery efficiencies. The majority of studies report data for particulates > 10 μm. Due to the associations between exposure to particles < 10 μm and human health effects, we recommend that prioritization efforts that develop standard protocols, based on existing air sampling methods capable of characterizing MPs < 10 μm are progressed.

Assessing reinforcing versus aversive consequences in a real-time secondhand smoke intervention.

Few studies have examined the relative effectiveness of reinforcing versus aversive consequences at changing behavior in real-world environments. Real-time sensing devices makes it easier to investigate such questions, offering the potential to improve both intervention outcomes and theory. This research aims to describe the development of a real-time, operant theory-based secondhand smoke (SHS) intervention and compare the efficacy of aversive versus aversive plus reinforcement contingency systems. Indoor air particle monitors were placed in the households of 253 smokers for approximately three months. Participants were assigned to a measurement-only control group (N = 129) or one of the following groups: 1.) aversive only (AO, N = 71), with aversive audio/visual consequences triggered by the detection of elevated air particle measurements, or 2.) aversive plus reinforcement (AP, N = 53), with reinforcing consequences contingent on the absence of SHS added to the AO intervention. Residualized change ANCOVA analysis compared particle concentrations over time and across groups. Post-hoc pairwise comparisons were also performed. After controlling for Baseline, Post-Baseline daily particle counts (F = 6.42, p = 0.002), % of time >15,000 counts (F = 7.72, p < 0.001), and daily particle events (F = 4.04, p = 0.02) significantly differed by study group. Nearly all control versus AO/AP pair-wise comparisons were statistically significant. No significant differences were found for AO versus AP groups. The aversive feedback system reduced SHS, but adding reinforcing consequences did not further improve outcomes. The complexity of real-world environments requires the nuances of these two contingency systems continue to be explored, with this study demonstrating that real-time sensing technology can serve as a platform for such research.

Species of Fungi and Pollen in the PM1 and the Inhalable Fraction of Indoor Air in Homes

Airborne microbial fragments in the PM1 fraction (particles with aerodynamic diameters less than 1 µm) are a cause for concern as they may potentially deposit in the alveoli of the human airways. This study aimed to use qPCR to identify and quantify 24 different species or groups of genera in the PM1 and the inhalation fraction (particles that may enter the mouth or nose during breathing) of indoor air and to relate this to what has previously been found for each species. Results showed that eight fungal species, and Aspergillus/Penicillium/Paecilomyces variotii, as well as Alnus/Corylus and actinobacteria belonging to the Streptomyces genus were detected both in the PM1 and the inhalable fraction. Five fungal species were only detected in the inhalable fraction. A significant effect of season was found on the fungal composition in the PM1 (p = 0.001) and the inhalable (p = 0.017) fraction. This study demonstrated that it is possible to use qPCR to identify and quantify different microbes in the PM1 fraction, and it has improved our understanding of the qualitative and quantitative relationship between the PM1 and the inhalable microbial particles in indoor air. Combined with the literature review it also shows a large variation within and between species in the share of fungi which is present as fragments.

Diffusion characteristics of the industrial submicron particle under Brownian motion and turbulent diffusion

The industrial release of submicron aerosol particles at workplace could cause undue health effect on workers. To effectively capture and remove airborne particles, we need to study the characteristics of various interactive particle motion forces (drag force, Brownian force, Saffman lift force, etc.) and the dispersion of these aerosol particles in indoor air. In this study, the dominant force of submicron particles was determined by calculating the acting forces with different particle sizes. Then, a Discrete Particle Model (DPM) was used to calculate the trajectory of particle movement in turbulent thermal plume flow. Horizontal dispersity ( DH) was defined to evaluate the horizontal diffusion of the particulate matter. The impact of different particle diameters, heat source temperatures and initial relative velocities on DH was investigated. This study showed that the main acting forces for submicron aerosol particles were drag force, Brownian force, Saffman lift force and thermophoresis force. Brownian force cannot be ignored when the particle diameter was below 0.3 µm, which would promote the irregular movement of particles in space and enhance their diffusion ability. The smaller the particle size, the higher the heat source temperature and the lower the particles' initial velocity would lead to the increase of DH.