Air Particulate Concentrations Research Articles

Effects of breath holding at low and high lung volumes on amount of exhaled particles

Exhaled breath contains particles originating from the respiratory tract lining fluid. The particles are thought to be generated during inhalation, by reopening of airways closed in the preceding expiration. The aim here was to explore processes that control exhaled particle concentrations. The results show that 5 and 10s breath holding at residual volume increased the median concentration of particles in exhaled air by 63% and 110%, respectively, averaged over 10 subjects. An increasing number of closed airways, developing on a timescale of seconds explains this behaviour. Breath holds of 5, 10 and 20s at total lung capacity decreased the concentration to 63%, 45% and 28% respectively, of the directly exhaled concentration. The decrease in particle concentration after breath holding at total lung capacity is caused by gravitational settling in the alveoli and associated bronchioles. The geometry employed here when modelling the deposition is however not satisfactory and ways of improving the description are discussed.

Ultrafine particle and fine trace metal (As, Cd, Cu, Pb and Zn) pollution episodes induced by industrial emissions in Huelva, SW Spain

Urban air quality impairment by ultrafine particles has become a matter of concern due to the adverse effects on human health. Most of the studies of ultrafine particles in urban air quality have focused on vehicle exhaust emissions. We studied how industrial emissions contribute to ultrafine particle concentrations in downwind urban ambient air. This research is based on experimental data collected in the ambient air of the industrial city of Huelva (SW Spain) over April 2008–December 2009 period (particle number, gaseous pollutants and black carbon concentrations and levels and chemical composition of PM10 and PM2.5 with daily and hourly resolution). This city is affected by emissions from the second largest Cu-smelter in Europe, phosphoric acid and fertilizer production plants and an oil refinery and petrochemical plant. Industrial emissions are the main cause of ultrafine particle episodes. When vehicle exhaust emissions are the main source, ultrafine particles typically show (24-h mean) concentrations within the range 14,700–5000 cm−3 (50th–1st), with 60% of these linked to this source and 30% to industrial emissions. In contrast, when daily mean levels of N are within the range 50,000–25,500 cm−3 (100th–70th), industrial and vehicle exhaust emissions accounted for 49 and 30%, respectively. High concentrations of toxic trace metals (As, Cu, Cd, Zn and Pb) were recorded when the study city suffered fumigations of the Cu-smelter plumes (e.g. 10–25 ng m−3 As, 1–2 ng m−3 Cd and >105 cm−3 of ultrafine particles). Because of these industrial emissions, ultrafine particle concentrations during daylight are about two times higher than those observed in other European cities. Recently, ultrafine particle emissions in vehicle exhausts have been subject to limit values in a recent stage of the EURO standards. Industrial emissions should also be considered.

Size distribution of chemical elements and their source apportionment in ambient coarse, fine, and ultrafine particles in Shanghai urban summer atmosphere

Ambient coarse particles (diameter 1.8-10 μm), fine particles (diameter 0.1-1.8 μm), and ultrafine particles (diameter < 0.1 μm) in the atmosphere of the city of Shanghai were sampled during the summer of 2008 (from Aug 27 to Sep 08). Microscopic characterization of the particles was investigated by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX). Mass concentrations of Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb, Sr, and Pb in the size-resolved particles were quantified by using synchrotron radiation X-ray fluorescence (SRXRF). Source apportionment of the chemical elements was analyzed by means of an enrichment factor method. Our results showed that the average mass concentrations of coarse particles, fine particles and ultrafine particles in the summer air were 9.38 2.18, 8.82 3.52, and 2.02 0.41 μg/m3, respectively. The mass percentage of the fine particles accounted for 51.47% in the total mass of PM10, indicating that fine particles are the major component in the Shanghai ambient particles. SEM/EDX results showed that the coarse particles were dominated by minerals, fine particles by soot aggregates and fly ashes, and ultrafine particles by soot particles and unidentified particles. SRXRF results demonstrated that crustal elements were mainly distributed in the coarse particles, while heavy metals were in higher proportions in the fine particles. Source apportionment revealed that Si, K, Ca, Fe, Mn, Rb, and Sr were from crustal sources, and S, Cl, Cu, Zn, As, Se, Br, and Pb from anthropogenic sources. Levels of P, V, Cr, and Ni in particles might be contributed from multi-sources, and need further investigation.

Size-resolved emission rates of airborne bacteria and fungi in an occupied classroom.

The role of human occupancy as a source of indoor biological aerosols is poorly understood. Size-resolved concentrations of total and biological particles in indoor air were quantified in a classroom under occupied and vacant conditions. Per-occupant emission rates were estimated through a mass-balance modeling approach, and the microbial diversity of indoor and outdoor air during occupancy was determined via rDNA gene sequence analysis. Significant increases of total particle mass and bacterial genome concentrations were observed during the occupied period compared to the vacant case. These increases varied in magnitude with the particle size and ranged from 3 to 68 times for total mass, 12–2700 times for bacterial genomes, and 1.5–5.2 times for fungal genomes. Emission rates per person-hour because of occupancy were 31 mg, 37 × 106 genome copies, and 7.3 × 106 genome copies for total particle mass, bacteria, and fungi, respectively. Of the bacterial emissions, ∼18% are from taxa that are closely associated with the human skin microbiome. This analysis provides size-resolved, per person-hour emission rates for these biological particles and illustrates the extent to which being in an occupied room results in exposure to bacteria that are associated with previous or current human occupants.Practical ImplicationsPresented here are the first size-resolved, per person emission rate estimates of bacterial and fungal genomes for a common occupied indoor space. The marked differences observed between total particle and bacterial size distributions suggest that size-dependent aerosol models that use total particles as a surrogate for microbial particles incorrectly assess the fate of and human exposure to airborne bacteria. The strong signal of human microbiota in airborne particulate matter in an occupied setting demonstrates that the aerosol route can be a source of exposure to microorganisms emitted from the skin, hair, nostrils, and mouths of other occupants.

Development of dry deposition velocity model for a typical medium level Indian city Karaikudi

In this study, day and night dry deposition samples were collected with Eagle II arrangement of dry deposition plates. Karaikudi, one of the medium level city in India has been the chosen as area of study. Sampling locations were classified as zone1, zone2 and zone3. Wind speed was also recorded during sampling. Particle size was determined by using X-ray diffractometer (XRD). Relation between particle size and dry deposition flux was also established. Different polynomials were tried to find out the best correlation between particle size and the dry deposition flux. Overall dry deposition velocity was calculated by taking slope of regression line between dry deposition flux and ambient concentration. Better correlation between wind speed and dry deposition flux was obtained during April ’08. The resultant correlation coefficient (R) was found to be 0.8401 and 0.7295 for day and night respectively for a linear relationship. Using the collected data, dry deposition velocity model was developed by which correlation coefficient (R) between modelled dry deposition velocity and calculated dry deposition velocity was arrived as 0.9981. The present methodology would eliminate the enormous task of collecting the ambient dry deposition air sample and particle concentration and analyse the same in the laboratory.

Atmospheric Particulate and Metallic Elements (Zn, Ni, Cu, Cd and Pb) Size Distribution at Three Characteristic Sampling Sites

The experiments of this study were carried out between November 2010 and December 2010 at three sampling sites in Taiwan: a school (Hung-kuang [HK]) and a wetland (Gao-mei [GM]) in Taichung, as well as at an industrial site (Quan-xing [QX]) in Changhua. A MOUDI-100S4 sampler was used to collect 1-day ambient suspended particles. The samples were weighed and analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) after collection. Concentrations of particulates of different sizes and their distribution were investigated. In addition, the ambient air metallic element concentrations and size distributions for Zn, Ni, Cu, Cd, and Pb were also studied. The results showed that the average ambient air particle concentrations order was Quan-xing (QX, industrial) > Hung-kuang (HK, school) > Gao-mei (GM, wetlands). The metallic elements Zn, Cu, Cd, and Pb were mainly distributed in coarse particles, while Ni was distributed in fine particles at the HK sampling site. Also, the metallic element Cu was the only element distributed in fine particles for the GM sampling site. The metallic elements Cu and Ni were the only elements associated with coarse particles at the QX sampling site. The results also indicated that the main contributions of ambient air pollutants for QX were from various industrial process and the main contributions for HK sampling site were from traffic and residual areas. The main contributions of ambient air pollutants for GM site likely came from long-range transport. The QX site had the highest average particle concentrations (PM18 = 21.91 μg/m3, PM10 = 20.45 μg/m3, PM2.5 = 22.13 μg/m3, PM1 = 25 μg/m3) compared with those from the other sampling sites in this study. This finding is likely due to its location in an industrial area. In addition, the results suggested that the main pollution source for QX is manufacturing plant emission, while the source for HK is traffic emission. Moreover, the main pollution source for GM (wetlands) may be long distance transportation when the wind is blown from northwest of mainland China.

Aerosols Analysis by LIBS for Monitoring of Air Pollution by Industrial Sources

In the context of the air quality improvement, there is an increasing need to monitor gas and particle emissions originating from exhaust stacks (incinerators, foundries, etc.) for regulation enforcement purposes. Lots of pollutants are targeted; among them, heavy metals are mostly found in particulate forms. Hence, there is a need to promote the development of suitable on line analytical techniques. To that end, laser-induced breakdown spectroscopy (LIBS) appears to be a good technique. Indeed, it is quantitative, fast (<1 min), requires no sample preparation, and can be performed at remote distance. The instrumentation is compact and offers the possibility to be used for continuous and in-situ monitoring. Two different approaches have been tested by several authors to analyze aerosols by LIBS, by focusing the laser either on particles collected on a filter or directly into the aerosol. In this work, these two approaches, aiming at measuring the mass concentration of micrometer metallic particles in air, are investigated and compared. The experimental setup includes an aerosol source (an ultrasonic nebulizer producing a diluted aerosol of CuSO4 particles) ; two sampling lines for particle sizes and, for reference concentration measurements, a line for direct LIBS analysis ; and a fourth one devoted to filter sampling for subsequent LIBS measurements. Calibration curves were obtained with those two experimental approaches and the results are compared. In terms of sampling particles number, indirect analysis appears to be more efficient than direct analysis for our experimental conditions. Better detection limits were found with direct analysis when comparing the two approaches under similar sampling conditions (analysis time and sampling flow).

Association between Tree Pollen Counts and Asthma ED Visits in a High-Density Urban Center

Background. Asthma exacerbation patterns are cyclic in nature and often correlate with air particle concentrations. Objective. To examine the relationship between asthma-related emergency department (ED) visits and outdoor air quality for pediatric and adult patients in a high asthma prevalence area, the New York City borough of the Bronx. Methods. Numbers of daily asthma-related adult and pediatric ED visits during one complete year (1999) were obtained from the seven major Bronx hospitals. Daily values of nitrogen oxides (NOx), ozone (O3), sulfur dioxide (SO2), and pollen counts were acquired. Results. Asthma-related ED visit numbers were highest in December–January and lowest in July. There were three distinct peaks of increased asthma ED visits: winter (December–January), spring (late April–May), and fall (October). The spring peak was the most striking and coincided with high tree pollen counts (tree pollen: r = 0.90, p = .03). We observed a positive correlation between asthma ED visits in the winter and SO2 and NOx levels. Winter peaks of SO2 and NOx in early December appeared to precede the winter asthma peak. Conclusions. The spring asthma peak is closely associated with increased tree pollen counts, and the asthma increase at this time is likely due to allergic reactions to pollen. No significant associations could be established with the fall peak. The winter peak correlates with elevated SO2 and NOx levels.

Indoor Air Particulates in Broiler Environment During Winter

2 Abstract: The impact of winter climate on indoor and outdoor air particulate concentrations (ID and ODPC), concentrations of TSP, sizes and nature in broiler houses were recorded weekly. In closed and Open houses (Chs and OHs) significant positive correlations were recorded between ID and OD climate. Significantly decreased ID Ta. C and A.V m/sec and increased RH% in open vs closed. OD Ta. C significantly decreased o o

Symmetric Inclined Grid Mobility Analyzer for the Measurement of Charged Clusters and Fine Nanoparticles in Atmospheric Air

The Symmetric Inclined Grid Mobility Analyzer (SIGMA) was developed for applications in atmospheric aerosol nucleation research with special attention to long-term routine measurements in natural atmospheric conditions. The new instrument was elaborated using the experience of the preceding scanning mobility analyzers Inclined Grid Mobility Analyzer (IGMA) and Balanced Scanning Mobility Analyzer (BSMA). The range of electric mobility is 0.032−3.2 cm2V−1s−1. The particle diameter distribution in the range of 0.4−7.5 nm is resolved considering the size-mobility correlation at air temperature and pressure measured with built-in sensors. The scanning technique ensures that possible peculiarities in the recorded size or mobility distribution are not caused by the technical troubles of individual mobility channels. High rate of air flow and isopotential principle suppress the disturbing effect of external electric fields and assure the representative sampling of air ions. The sheath air is coming from the atmosphere together with the sample air and is deionized by means of electrostatic filters. The residence time of the air in the instrument is 0.16 s and the temperature change does not exceed 0.5 K. Different of the previous instruments the positive and negative air ions are sampled from the same inlet air flow and measured exactly simultaneously. The sensitivity of the instrument is increased and allows measuring the mobility fraction concentrations of charged fine nanometer particles in atmospheric air at a standard 5-min time resolution with random errors of about 1 cm−3. The time resolution of 20 s is available at random errors of about 5 cm−3.

Monitoring of Ambient Air Particles and Inorganic Elements in China and Korea during an Asian Dust Storm

Concentrations of ambient air particles such as total suspended particulates (TSP), particulate matter <TEX>$(PM)_{10}$</TEX>, and <TEX>$PM_{2.5}$</TEX>, were monitored simultaneously from May to June, 2007, at four locations at Alashan and Beijing in China, and Seoul and Gosan in South Korea. These monitoring sites are in the pathway of Asian dust (AD) storms traveling from China to the Korean peninsula. An AD event was observed in the Korean peninsula on May 25-26. During the sampling period, the average concentrations of TSP and PM10 were each higher than <TEX>$150\;{\mu}g/m^3$</TEX> in Alashan and Beijing, but not in Seoul and Gosan. The concentration of TSP in Alashan (where the dust storm originated) on the day of the AD event reached <TEX>$1824.7\;{\mu}g/m^3$</TEX>, this being the highest concentration of air particles observed during the sampling period. The level was decreased to 15% of this (<TEX>$274.7\;{\mu}g/m^3$</TEX>) in Seoul and to 8.7% (<TEX>$159.0\;{\mu}g/m^3$</TEX>) in Gosan when the AD was observed two days later in Korea. Gosan, a representative background site in East Asia, displayed the lowest concentration of particles, with this maximal TSP concentration of <TEX>$159\;{\mu}g/m^3$</TEX>. Inorganic element contents in the air particles were also measured, and the concentrations in the four different regions compared. Concentrations of anthropogenically-enriched heavy metals in <TEX>$PM_{10}$</TEX> and <TEX>$PM_{2.5}$</TEX>, such as lead, arsenic, cadmium, and mercury, were higher in the metropolitan cities of Beijing and Seoul compared to non-industrialized regions of Alashan and Gosan. However, the concentrations of inorganic soil elements including iron, magnesium, aluminum sodium, and manganese, were higher in Alashan compared to those in other sampling sites.

Optical and microphysical parameters of arid dust aerosol

The parameters of heavily dusty air in an aerosol chamber under the conditions of an arid zone are studied. The transmission, optical density, Angstrom parameter, aerosol absorption coefficient, and visibility range are calculated. The temporal and spectral dependences of the optical parameters are analyzed. The regularities of the particle-size distribution function in strongly inhomogeneous dust aerosol are studied for coarsely (with a diameter more than 1 μm) and finely dispersed (with a diameter of less than 1 μm) fractions. The sizes and concentrations of the aerosol particles in air were determined using a photoelectric aerosol counter together with a 15-channel analyzer. We present the absorption spectra of coarsely and finely dispersed dust aerosol collected under different meteorological conditions. The possible mechanisms of variations in the aerosol disperse composition are analyzed.

Quantitative assessment of volcanic ash hazards for health and infrastructure at Mt. Etna (Italy) by numerical simulation

We performed a quantitative hazard assessment to determine the potential impacts of volcanic tephra fall on human health and infrastructure in the vicinity of Mt. Etna (Italy). Using the numerical model VOL-CALPUFF, we explored the dynamics of long-lasting weak plume eruptions and their effects on the surrounding region. Input data are based on credible estimates of the main parameters characterising the expected events as derived from the historically observed and reconstructed explosive record of Mt. Etna. Monte Carlo techniques are used to capture the effects on estimates of finer ash concentration and total ground deposition due to volcanological uncertainties and meteorological variability. Numerical simulations compute the likelihoods of experiencing critical 10-μm volcanic particle (VP 10) concentrations in ambient air and tephra ground deposition at various populated locations around the volcano, including the city of Catania, and at key infrastructure, such as airports and main roads. Results show how the towns and infrastructure on the east side of the volcano are significantly more exposed to ash-related hazards than those on the west side, in accordance with wind statistics. Simulation outcomes also illustrate how, at the sites analysed, the amount of deposited particulate matter is proportional to the intensity (i.e. mass flow rate) of the event whereas predicted values of VP 10 concentrations are significantly larger for smaller events due to the reduced dispersal of low altitude plumes. The use of a simple re-mobilization model highlights the fact that particle re-suspension needs to be considered in the estimation of VP 10 values. Our findings can be used to inform civil protection agencies responsible for mitigating tephra fall impacts to human health, road transport and aviation safety.

GIS spatial analysis of population exposure to fine particulate air pollution in Beijing, China

This research diagnoses the exposure of the residential population and the vulnerable groups of children and elderly people to air particle pollution in urban Beijing. We surveyed the air particle pollutant concentrations in the field. We used a universal kriging model in a geographic information system to interpolate the spatial distributions of each pollutant. Spatial patterns of air particle pollution were overlaid to community-level population distributions to identify the community exposures to high air particle pollution. Spatial and statistic modeling reveals that high concentration of ultra-fine air particles of particulate matter (PM) 0.3 m is strongly associated with high-population urban communities in the southwest and central western areas in the winter season. By contrast, all the other particle sizes surveyed (PMs of 0.5, 1.0, 3.0, and 5.0 m) indicate that high concentrations in the summer are associated with high-population communities. Reversed spatial and temporal patterns between PM 0.3 m and other particle sizes suggest that PM 0.3 m may have different sources of origin.

A simplified methodology for the prediction of mean air velocity and particle concentration in isolation rooms with downward ventilation systems

Calculating the velocity and particle concentration indoor is critical for isolation rooms design. Computational fluid dynamics (CFD) is regarded as a powerful tool aiding in the indoor environment design for isolation rooms by enabling us to predict the velocity and particle concentration distribution in detail. However, CFD method is time-consuming and relatively expensive, especially for actual engineering application. So this study proposes a simplified methodology to predict the mean air velocity and particle concentration in the occupied zone of isolation rooms with downward ventilation systems. The methodology is based on a similarity theory analysis, by which the key similarity criteria are deduced. The correlating equation to calculate the mean air velocity and particle concentration in the occupied zone in isolation rooms is established by multiple linear regression (MLR) which is based on the numerical test results obtained by CFD. The equation correlates the mean air velocity and particle concentration with air supply volume rate, indoor particle generating rate, and other parameters. The calculated results agree with those from measurement and CFD simulations for the studied cases, generating a relative error less than 25%. It could offer the engineers a simpler path to calculate the mean air velocity and particle concentration.

Airborne Particles in Swansea, UK: Their Collection and Characterization

Urban air particulate matter (PM) has previously been associated with a variety of adverse health effects. It is now believed that the smallest particles, ultrafine or nanoparticles, are linked to the greatest health effects. The physicochemistry of these particles is likely to provide information regarding their toxicity. Therefore, the aim of this study was to further the understanding of the heterogeneous and changing particle concentrations in urban air, in conjunction with gaining an understanding of the physicochemistry of the particles. A Dekati electrical low-pressure impactor was used to collect the particles and real-time data in a busy traffic corridor in Swansea, Wales, over a period of 10 nonconsecutive weeks. Particle concentrations in the street canyon were analyzed and particle physicochemistries investigated using a variety of techniques. Particle number concentrations were found to vary both diurnally and from day to day in the traffic corridor. Of all particles, the nano to fine size fraction was consistently identified in the highest concentrations (maximum: 140,000 particles cm−3). Particle physicochemistry was found to vary as a function of size, with larger particles exhibiting a greater variety of morphologies (and consequently particle types) and associated metals.

Extracellular glutamate level and NMDA receptor subunit expression in mouse olfactory bulb following nanoparticle-rich diesel exhaust exposure

In this present study, we aimed to investigate the extracellular glutamate level and memory function-related gene expression in the mouse olfactory bulb after exposure of the animals to nanoparticle-rich diesel exhaust (NRDE) with or without bacterial cell wall component. Lipoteichoic acid (LTA), a cell wall component derived from Staphylococcus aureus, was used to induce systemic inflammation. Male BALB/c mice were exposed to clean air (particle concentration, 4.58 μg/m3) or NRDE (148.86 μg/m3) 5 h per day on 5 consecutive days of the week for 4 wk with or without weekly intraperitoneal injection of LTA. We examined the extracellular glutamate levels in the olfactory bulb using in vivo microdialysis and high-performance liquid chromatography assay. Then, we collected the olfactory bulb to examine the expression of N-methyl-D-aspartate (NMDA) receptor subunits (NR1, NR2A, and NR2B) and calcium/calmodulin-dependent protein kinase (CaMK) IV and cyclic AMP response element binding protein (CREB)-1 using real-time reverse-transcription polymerase chain reaction (RT-PCR). NRDE and/or LTA caused significantly increased extracellular glutamate levels in the olfactory bulb of mice. Moreover, the exposure of mice to NRDE upregulates NR1, NR2A, NR2B, and CaMKIV mRNAs in the olfactory bulb, while LTA upregulates only NR2B and CREB1 mRNAs. These findings suggest that NRDE and LTA cause glutamate-induced neurotoxicity separately and accompanied by changes in the expression of NMDA receptor subunits and related kinase and transcription factor in the mouse olfactory bulb. This is the first study to show the correlation between glutamate toxicity and memory function-related gene expressions in the mouse olfactory bulb following exposure to NRDE.

Short-term impact of particulate matter (PM 2.5) on daily mortality among the over-75 age group in Madrid (Spain)

Background The 2006 World Health Organization Air Quality Guidelines recommend using particulate matter having a diameter of under 2.5 micra (PM 2.5) rather than PM 10 as an indicator of air particle concentration, a pattern followed by new European directives. Nevertheless, few studies have analysed this new indicator's impact at a European level on daily mortality among a high-risk group, such as persons aged over 75 years. Objective This study sought to analyse and quantify the effect of PM 2.5 on daily cause-specific mortality among the over-75 age group in the city of Madrid. Methods Using Poisson regression with Generalized Additive Models (GAM), a longitudinal, ecological time-series study examined the following causes of death: all causes except accidents (International Classification of Diseases-9th revision (ICD 9): 1-799); circulatory causes (ICD 9: 390-459); and respiratory causes (ICD 9: 460-519). These were adjusted for other chemical, biotic and acoustic pollutants. Further control variables considered were: trend; seasonality; influenza epidemics; and autocorrelation between mortality series. Results A significant statistical association was detected between daily mean PM 2.5 particle concentrations and all-cause mortality in the city of Madrid. This association was not in evidence for PM 10 concentrations. The Relative Risks found for an increase of 25 µg/m 3 in PM 2.5 concentrations were as follows: all-cause mortality, 1.057 (1.025–1.088); circulatory-cause mortality, 1.088 (1.041–1.135); and respiratory-cause mortality, 1.122 (1.056–1.189). The Attributable Risks were 5.41%, 8.12% and 10.90% respectively. This effect was observed in the short term (lags 1–2). Conclusion Our results indicate a strong impact of PM 2.5 concentrations on daily mortality among the over-75 age group in Madrid, and underscore the need for measures aimed at lowering the concentration levels of this primary air pollutant in large cities, particularly by reducing motor vehicle traffic, the main source of such pollutant emission in urban atmospheres.

Optimization of bathroom ventilation design for an ISO Class 5 clean ward

Ventilation is a main method to control the contaminant dispersion within clean wards. In this paper, we investigated the effects of various ventilation designs of the bathroom in an ISO Class 5 clean ward. Specifically, the contaminant dispersion and particle concentrations corresponding to three different ventilation design schemes were characterized and compared using computational fluid dynamics (CFD) analysis. For each design, we examined airflow and particle concentrations for contaminant sources located at two places (i.e., at the toilet seat and on the floor), respectively. Field test was conducted to compare the measured and simulated air velocities and particle concentrations in a hospital clean ward. The implemented CFD modeling of ventilation effects of various designs in this study has proven to accurately characterize airflow and contaminant control in the ventilated space, and has led to optimizing ventilation for the bathroom in an ISO Class 5 clean ward.

Measurements of the atmospheric concentrations of nitrogen dioxide using the radiation absorption in a spectral range of 415 nm

The trace atmospheric concentrations of NO2 are measured with the methods of the diode laser absorption spectroscopy and the phase shift of the modulated radiation. An electronic transition in a range of 415 nm is employed. For a measurement time of 20 ms, the sensitivity of the concentration measurements is about 10−11 relative to the concentration of air particles (0.02 ppbv). At a time interval of 5–10 min, the reproducibility of the absolute concentration measurements (0.1 ppbv) is limited by the low-frequency fluctuations of the optical parameters of the spectrometer and the calibration system and corresponds to the level determined by the Allan variance.