Evaluation of source model coupled computational fluid dynamics (CFD) simulation of the dispersion of airborne contaminants in a work environment

Dispersion of airborne contaminants in indoor air was evaluated employing physical measurement, empirical models, and computer simulation methods. Field data collected from a tray of evaporating solvent in the laboratory were compared with computational fluid dynamics (CFD) simulations coupled with evaporation models. The results indicated that mathematical models of evaporation can be coupled with CFD simulations to produce reasonable qualitative predictions of airborne contaminant levels. The airflow pattern within a room is primarily determined by the room layout and the position of the air supply diffusers. Variations in ventilation rate did not alter the airflow pattern, thus generating a characteristic concentration profile of the airborne contaminants.     

客房内空气品质调查

目的 了解广州市宾馆客房的室内空气污染状况。方法 采用SPSS12．0进行数据分析和空气质量综合指数法进行综合评价。结果 客房内物理性参数夏季大部分在合格范围内，冬季温度和相对湿度有部分超过标准；客房内的空气属于未污染，各参数实测的平均浓度均在室内空气质量标准所规定的范围之内，各参数指数在0．27-0．63，超标率较低。结论 客房应加强通风除湿，空气质量综合指数法简捷适用，值得推广。     

Characterization of indoor settled dust and investigation of indoor air quality in different micro-environments

Present study reports the characterization results of settled dust particles in different indoor micro-environments of an academic institution in India. Field emission scanning electron microscope analysis of indoor dust revealed the presence of mineral particles, fly ash, and soot particles of different morphologies. Energy-dispersive X-ray spectroscopy analysis of indoor dust indicated that crystal particles are comprised of elements such as C, O, Na, Mg, Al, Si, S, Cl, K, Ca, Fe, and Ti. These elements accounted for more than 99% of the samples. The average content of O (42.7%) and C (18.9%) in the dust particles was found to be higher than their natural abundances. The concentrations of PM₁₀, PM_2.5, and PM₁ were observed in the range of 88–58, 37–33, 23–29 µg/m³, respectively. Except temperature, other parameters such as volatile organic carbon, carbon dioxide concentration, and relative humidity were found to be within comfort limits of American Society of Heating, Refrigerating, and Air-Conditioning Engineers.

Abbreviations: ASHRAE: American Society of Heating, Refrigerating, and Air-Conditioning Engineers; CO₂: carbon dioxide; COPD: chronic obstructive pulmonary disease; EDX: energy-dispersive X-ray; FESEM: field emission scanning electron microscope; FTIR: Fourier transform infrared spectroscopy; IAP: indoor air pollution; IAQ: indoor air quality; HAP: household air pollution; OAP: outdoor air pollution; PM: particulate matter; VOC: volatile organic carbon; WHO: World Health Organization     

Assessment of exposure to indoor air contaminants from combustion sources: methodology and application

A methodology for assessing indoor air pollutant exposures is presented, with specific application to unvented combustion by-products. This paper describes the method as applied to a study of acute respiratory illness associated with the use of unvented kerosene space heaters in 333 residences in the New Haven, Connecticut, area from September 1982 to April 1983. The protocol serves as a prototype for a nested design of exposure assessment which could be applied to large-scale field studies of indoor air contaminant levels. Questionnaires, secondary records, and several methods of air monitoring offer a reliable method of estimating environmental exposures for assessing associations with health effects at a reasonable cost. Indoor to outdoor ratios of NO2 concentrations were found to be 0.58 +/- 0.31 for residences without known sources of NO2. Levels of NO2 were found to be comparable for homes with a kerosene heater only and those with a gas cooking stove only. Homes with a kerosene heater and a gas stove had average two-week NO2 levels approximately double those with only one source. Presence of tobacco smokers had a small but significant impact on indoor NO2 levels. Two-week average levels of indoor NO2 were found to be excellent predictors of total personal NO2 exposure for a small sample of adults. Residences with kerosene space heaters had SO2 levels corresponding to the number of hours of heater use and the sulfur content of the fuel. Formaldehyde levels were found to be low and not related to unvented combustion sources. NO2, SO2, and CO2 levels measured in some of the residences were found to exceed those levels specified in current national health standards.     

基于室内CO_2浓度标准值的临界新风量研究

目的探讨满足室内CO_2浓度标准值实际所需要的最小通风量,即临界新风量;为室内通风量的设计和改善室内空气质量提供依据。方法对不同新风量和室内人数条件下某室内空间(体积V0=37.5 m~3)的CO_2浓度进行监测并对其变化趋势进行拟合。结果室内CO_2实测浓度变化符合y=b+ae-kt型指数曲线。在门窗紧闭的条件下,对不同新风量时室内CO_2实测值进行y=b+ae-kt型指数曲线拟合,可得出自然渗透风量V1=11.5 m~3/h,新风系统风量V3=60 m~3/h时的有效新风量V2=20.1 m~3/h;本实验条件下的新风系统通风效率E只有34%。该室内空间所需要的临界新风量(满足CO_2标准限值1 000 ml/m~3要求所需要的最小新风量)V4=74n-32(n:室内人数)。结论新风系统能够有效控制室内CO_2浓度,临界新风量与室内人员数量呈线性相关。     

对透析液和透析用水细菌污染的调查分析

目的:调查透析液和透析用水细菌污染的原因.方法:按《医院感染管理规范》的要求检测并鉴定致病菌.结果:透析液和透析用水、B液、软水口、配液容器培养出致病菌和条件致病菌.结论:血液透析液和透析用水细菌污染与软水机过滤器和反渗膜使用时间过长引起破损,未能及时更换,以及B液配制过程中细菌污染有关.     

Sampling efficiency of modified 37-mm sampling cassettes using computational fluid dynamics

In the U.S., most industrial hygiene practitioners continue to rely on the closed-face cassette (CFC) to assess worker exposures to hazardous dusts, primarily because ease of use, cost, and familiarity. However, mass concentrations measured with this classic sampler underestimate exposures to larger particles throughout the inhalable particulate mass (IPM) size range (up to aerodynamic diameters of 100 μm). To investigate whether the current 37-mm inlet cap can be redesigned to better meet the IPM sampling criterion, computational fluid dynamics (CFD) models were developed, and particle sampling efficiencies associated with various modifications to the CFC inlet cap were determined. Simulations of fluid flow (standard k-epsilon turbulent model) and particle transport (laminar trajectories, 1–116 μm) were conducted using sampling flow rates of 10 L min^?1 in slow moving air (0.2 m s^?1) in the facing-the-wind orientation. Combinations of seven inlet shapes and three inlet diameters were evaluated as candidates to replace the current 37-mm inlet cap. For a given inlet geometry, differences in sampler efficiency between inlet diameters averaged less than 1% for particles through 100 μm, but the largest opening was found to increase the efficiency for the 116 μm particles by 14% for the flat inlet cap. A substantial reduction in sampler efficiency was identified for sampler inlets with side walls extending beyond the dimension of the external lip of the current 37-mm CFC. The inlet cap based on the 37-mm CFC dimensions with an expanded 15-mm entry provided the best agreement with facing-the-wind human aspiration efficiency. The sampler efficiency was increased with a flat entry or with a thin central lip adjacent to the new enlarged entry. This work provides a substantial body of sampling efficiency estimates as a function of particle size and inlet geometry for personal aerosol samplers.     

An investigation of the co-variation in circulating levels of a large number of environmental contaminants

We are daily exposed to many different environmental contaminants. Mixtures of these contaminants could act together to induce more pronounced effects than the sum of the individual contaminants. To evaluate the effects of such mixtures, it is of importance to assess the co-variance amongst the contaminants. Thirty-seven environmental contaminants representing different classes were measured in blood samples from 1016 individuals aged 70 years. Hierarchical cluster analysis and principal component analysis were used to assess the co-variation among the contaminants. Within each identified cluster, possible marker contaminants were sought for. We validated our findings using data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 study. Two large clusters could be identified, one representing low/medium chlorinated polychlorinated biphenyls (PCBs) (≤6 chlorine atoms), as well as two pesticides and one representing medium/high chlorinated PCBs (≥6 chlorine atoms). PCBs 118 and 153 could be used as markers for the low/medium chlorinated cluster and PCBs 170 and 209 could be used as markers for the medium/high chlorinated cluster. This pattern was similar to data from the NHANES study. Apart from the PCBs, little co-variation was seen among the contaminants. Thus, a large number of chemicals have to be measured to adequately identify mixtures of environmental contaminants.     

室内生物源性污染物对健康影响的研究进展

室内空气质量与人体健康密切相关。随着空调普及导致室内空气循环减少以及家庭宠物的流行等,为室内微生物的生存和繁殖提供了条件。空气中的微生物及其产生的毒素、致敏原经常附着于飞沫及颗粒物上,降落地面或长时间漂浮空气中形成微生物气溶胶。长期暴露于生物源性污染物可能对人体造成健康危害,以呼吸系统病变(如慢性阻塞性肺部疾患,炎症等)和变态反应(如变应性鼻炎,肺炎及哮喘等)为主。本文对近十年来有关空气生物源性污染物的研究进展进行综述。     

Characterization of indoor air contaminants in a randomly selected set of commercial nail salons in Salt Lake County,Utah, USA

Air samples were collected in 12 randomly selected commercial nail salons in Salt Lake County, Utah. Measurements of salon physical/chemical parameters (room volume, CO₂ levels) were obtained. Volatile organic compound (VOC) concentrations were collected using summa air canisters and sorbent media tubes for an 8-h period. Multivariate analyses were used to identify relationships between salon physical/chemical characteristics and the VOCs found in the air samples. The ACGIH^® additive mixing formula was also applied to determine if there were potential overexposures to the combined airborne concentrations of chemicals monitored. Methyl methacrylate was detected in 58% of the establishments despite having been banned for use in nail products by the state of Utah. Formaldehyde was found above the NIOSH REL^® (0.016?ppm) in 58% of the establishments. Given the assortment of VOCs to which nail salon workers are potentially exposed, a combination of engineering as well as personal protective equipment is recommended.     

合肥市干洗作业环境空气中四氯乙烯含量的调查

随着科技的不断进步,服装面料不断出新,对洗涤的要求也越来越高,干洗业因而得以迅速发展.但作为干洗剂主要成分的四氯乙烯(perchloroethylene, PCE)对人体有一定的毒副作用,慢性中毒可引起功能性中枢神经系统抑制以及对肝、肾、心脏和皮肤的毒作用;急性中毒可使人昏迷,严重时可致死[1].我们对合肥市具有代表性的三家大型干洗店进行了现场采样调查,以了解干洗从业人员所处的工作环境中四氯乙烯的含量情况.     

A new design and computational fluid dynamics study of an implantable axial blood pump

Considering small thoracic space, using implantable ventricular assist device requires reduction in a pump size. Among many available blood pumps, axial blood pumps have attracted greatly because of their small size. In this article, a new miniature axial blood pump has been designed and studied which can be easily implanted in the human body. In this design, the pump overall length decreased by a little increasing in the pump diameter, and new blade geometry is used to produce a streamlined, idealized, and nonobstructing blood flow path in the pump. By means of computational fluid dynamic, the flow pattern through the pump has been predicted and overall pump performance and efficiency has been computed. Also, to ensure a reliable VAD design, two methods for checking wall shear stress were used to confirm that this pump wouldn’t cause serious blood damage.     

室内空气甲醛污染相关问题研究进展

室内空气甲醛污染问题已成为全球的公共卫生问题,受到各国的重视和人们的普遍关注。此文以近年知网和Pubmed等数据库研究报道为基础,对室内空气甲醛污染相关报道情况进行分析,从室内空气中甲醛的危害、室内空气中甲醛的来源与暴露和室内空气中甲醛去除方法三个方面进行综述。对甲醛危害方面主要就甲醛致癌、导致白血病、导致过敏及其他毒性四个方面进行总结;在甲醛来源与暴露方面就家居装修、室内气体燃烧不完全和职业暴露等几方面对文献进行梳理;在甲醛消除方面主要总结吸附剂吸附法、光催化方法和植物吸附法等方法,为室内空气甲醛污染的防治提供借鉴。     

Quantitative assessment of indoor air pollutants in workplaces

This article presents the results of quantitative assessment of indoor air pollutants (IAP) in the workplaces of King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia. Twenty two workplaces were scheduled for four quantitative IAP measurement sessions, i.e., summer day, summer night, winter day, and winter night. The concentrations of five indoor air contaminants, i.e. formaldehyde (HCHO), carbon dioxide (CO ), carbon monoxide (CO), sulfur dioxide (SO ), and total hydrocarbons, in 2 2 addition to air temperature and relative humidity were measured and reported during each session. This was accomplished using the Bruel and Kjaer Multi-gas Monitor Type 1302. Quantitative analysis of the results show that 65% of the highest concentrations recording of all contaminants had developed during the summer day measurement in the respective locations. On the other hand, over 80% of the lowest concentrations reported for each location were detected during the winter night sessions. Day concentrations were always higher than night concentrations. Locations with higher contaminants' concentrations and causes were identified.     

An indoor air quality evaluation in a residential retrofit project using spray polyurethane foam

Understanding of indoor air quality (IAQ) during and after spray polyurethane foam (SPF) application is essential to protect the health of both workers and building occupants. Previous efforts such as field monitoring, micro-chamber/spray booth emission studies, and fate/transport modeling have been conducted to understand the chemical exposure of SPF and guide risk mitigation strategies. However, each type of research has its limitation and can only reveal partial information on the relationship between SPF and IAQ. A comprehensive study is truly needed to integrate the experimental design and analytical testing methods in the field/chamber studies with the mathematical tools employed in the modeling studies. This study aims to bridge this gap and provide a more comprehensive understanding on the impact of SPF to IAQ. The field sampling plan of this research aims to evaluate the airborne concentrations of methylene diphenyl diisocyanate (MDI), formaldehyde, acetaldehyde, propionaldehyde, tris(1-chlor-2-propyl)phosphate (TCPP), trans-1-chloro-3,3,3-trifluoropropene (Solstice^TM), and airborne particles. Modifications to existing MDI sampling and analytical methods were made so that level of quantification was improved. In addition, key fate and transport modeling input parameters such as air changes per hour and airborne particle size distribution were measured. More importantly, TCPP accumulation onto materials was evaluated, which is important to study the fate and transport of semi-volatile organic compounds. The IAQ results showed that after spray application was completed in the entire building, airborne concentrations decreased for all chemicals monitored. However, it is our recommendation that during SPF application, no one should return to the application site without proper personal protection equipment as long as there are active spray activities in the building. The comparison between this field study and a recent chamber study proved surface sorption and particle deposition is an important factor in determining the fate of airborne TCPP. The study also suggests the need for further evaluation by employing mathematical models, proving the data generated in this work as informative to industry and the broader scientific community.     

An improved passive activated C collector for measuring environmental 222Rn in indoor air

A modified version of an activated C monitor has been developed for the time-weighted average measurement of 222Rn for periods ranging from 1-7 d. The new collector consists of a metal can containing 50 g of activated C with a sintered metal filter covering the 3.2-cm diameter sample port in its lid. The new configuration reduces the adsorption and desorption rate of both 222Rn and water vapor by a factor of 4-5, as compared to an open-faced canister. The device measures the average 222Rn concentration accurately, even if the 222Rn concentration varies by more than a factor of 10. For practical situations encountered indoors, the modified collector yields results that are accurate to within +/- 10%. The integration time constant of the collector, tested at relative humidities ranging from 23-75%, is 9-11 d, which is more than three times longer than that of existing diffusion barrier collectors. It is simple to use, inexpensive (total cost of materials is +3.50), maintenance-free, easily sent and returned in the mail (total weight = 100 g), and is reusable for multiple exposures after simple regeneration by heating. The lower limit of detection for a 10-min counting interval is 7 Bq m-3 (0.2 pCi L-1) when counted within 3 d after the end of exposure.