Particle concentrations in data centers

Cooling buildings with large airflow rates of outside air when temperatures are favorable is an established energy-saving measure. In data centers, this strategy is not widely used, owing to concerns that it would cause increased indoor levels of particles of outdoor origin, which could damage electronic equipment. However, environmental conditions typical of data centers and the associated potential for equipment failure are not well characterized. This study presents the first published measurements of particle concentrations in operating data centers. Indoor and outdoor particle measurements were taken at eight different sites in northern California for particulate matter 0.3–5.0 μm in diameter. One of the data centers has an energy-efficient design that employs outside air for cooling, while the rest use conventional cooling methods. Ratios of measured particle concentrations in the conventional data centers to the corresponding outside concentrations were significantly lower than those typically found in office or residential buildings. Estimates using a material-balance model match well with empirical results, indicating that the dominant particle sources and losses have been identified. Measurements taken at the more energy-efficient site show nearly an order of magnitude increase in particle concentration when ventilation rates were high. The model indicates that this increase may be even higher when including particles smaller than the monitoring-equipment size limitation. Even with the increases, the measured particle concentrations are still below concentration limits recommended in industry standards.     

Indoor air quality and academic performance

I examine the effect of school indoor air quality (IAQ) on academic outcomes. I utilize a quasi-natural experiment, in which IAQ-renovations were completed at virtually every school in a single Texas school district at different points in time, combined with a panel of student-level data to control for many confounding factors and thereby uncover the causal effect of IAQ-renovations on academic outcomes. Results indicate that performance on standardized tests significantly improves while attendance is unresponsive to improvements in IAQ. Rough calculations suggest that IAQ-renovations may be a more cost-effective way to improve standardized test scores than class size reductions.     

建筑室内环境安全灰色评价模型及应用

人们在重视治理大气和江河湖海等大环境安全问题的时候 ,却忽视了直接危害人身健康甚至生命的室内环境安全问题。在现代社会 ,室内环境安全已经成为影响人们身心健康与安全的重要因素。由于影响室内环境安全的因素复杂 ,科学合理地评价其安全状况对改善室内环境安全具有重要意义。笔者针对建筑室内环境安全系统特征 ,在合理确定评价指标体系的基础上 ,建立了基于灰色关联理论的室内环境安全评价模型 ,并给予了实例验证 ,为室内环境安全评价提供了具有指导意义的技术和方法。     

室内环境中化学污染物质测定法研究

室内环境中化学污染物质的测定是研究和解决室内环境问题的基础。本文以甲醛和挥发性有机化合物两种室内环境中的主要化学污染物质为例,介绍了目前世界各国采用的各种测定法及其动向,并探讨了测定时期、测定时间、采样点布置等有关问题,提出了一些看法供参考。     

Preparation and characteristics of high performance paper containing titanium dioxide photocatalyst supported on inorganic fiber matrix

A novel paper-based material containing titanium dioxide (TiO₂) photocatalyst was successfully prepared by a papermaking technique with the internal addition of inorganic fibers on which TiO₂ particles were supported. Photodegradation performance of acetaldehyde gas, an indoor pollutant, and the durability of the TiO₂-containing papers were investigated under UV irradiation. Ceramic fiber suspension and polydiallyldimethylammonium chloride as a cationic flocculant were mixed, followed by the addition of TiO₂ suspension and anionic polyacrylamide. Subsequently, the inorganic mixture was poured into a pulp suspension, and TiO₂ handsheets then prepared by a papermaking method. The tensile strength of TiO₂-containing paper without a ceramic carrier decreased by more than 30% after 240-h UV irradiation (2 mW/cm²), although the strength of the TiO₂ sheet with ceramic fibers remained reasonably stable. The efficiency of acetaldehyde decomposition by the TiO₂ paper containing an inorganic carrier was nearly equal to that of the carrier-free TiO₂ paper. Scanning electron microscopic observation suggested that most TiO₂ particles were predominantly supported on the inorganic fiber matrix, and were mostly out of contact with organic pulp fibers. The TiO₂ paper with an inorganic carrier demonstrated both excellent photocatalytic performance and durability, which before had been mutually incompatible for organic materials containing TiO₂ photocatalyst. The two-stage mixing procedure for TiO₂ sheet-making is promising for the simple manufacture of high performance paper with photocatalytic ability.     

全尺度室内环境模拟箱研制及性能测评

介绍了全尺度室内环境模拟箱,以及研究开发的与室内实际空间尺寸相仿的大容量环境模拟箱具备的对试验条件的调节功能.在标准试验条件(箱内温度23 ℃,相对湿度45%,换气量30 m3/h)下,箱内温度、相对湿度和换气量的波动误差分别为0.21 ℃、0.35%、0.15 m3/h.实验结果表明,环境模拟箱的气密性和混合性良好,本底浓度较低,能为室内空气污染研究提供环境条件稳定、背景干扰小的室内仿真环境.对大芯板甲醛释放测定的结果表明,环境模拟箱能够较准确地模拟室内污染物的释放过程和规律.     

杭州市居室空气中芳香族化合物污染现状及其来源解析

用热解吸/气质联用技术研究了杭州市居室空气中芳香族化合物的组成。结果表明,杭州市居室空气中共存在60种芳香族化合物,其中苯系化合物48种,非苯芳香族化合物12种,检出率大于50%的23种;苯、甲苯、乙苯、苯乙烯、邻二甲苯、间(对)-二甲苯等10种化合物的总含量之和大于85.39%,是室内空气中主要的芳香族污染物,除萘外,其他22种污染物的平均浓度值均随装修时间间隔延长而降低;污染物主要来源是室内装修过程中使用的或装修材料中残留的有机溶剂、机动车辆排放的尾气、居民家庭中常用的清洁用品及含萘等成分的防蛀剂。     

室内安全生态学构建——室内安全生态学导论

根据现代室内日益严重的危害和安全问题 ,以及当今人类对安全健康的追求 ,依据科学学原理和学科建设原则 ,对“室内安全生态学”新兴学科进行了构建 ,笔者论述了构建“室内安全生态学”的原因和必要性 ,简单阐述了“室内安全生态学”的定义 ,讨论了“室内安全生态学”的主要研究内容、知识构成和骨干学科等问题     

Per- and polyfluorinated compounds (PFCs) in house dust and indoor air in Catalonia, Spain: implications for human exposure

A total of 27 per- and polyfluorinated compounds (PFCs) were determined in both house dust (n = 10) and indoor air (n = 10) from selected homes in Catalonia, Spain. Concentrations were found to be similar or lower than those previously reported for household microenvironments in other countries. Ten PFCs were detected in all house dust samples. The highest mean concentrations corresponded to perfluorodecanoic acid (PFDA) and perfluorononanoic acid (PFNA), 10.7 ng/g (median: 1.5 ng/g) and 10.4 ng/g (median: 5.4 ng/g), respectively, while the 8:2 fluorotelomer alcohol (FTOH) was the dominating neutral PFC at a concentration of 0.41 ng/g (median: 0.35 ng/g). The indoor air was dominated by the FTOHs, especially the 8:2 FTOH at a mean (median) concentration of 51 pg/m³ (median: 42 pg/m³). A limited number of ionic PFCs were also detected in the indoor air samples. Daily intakes of PFCs were estimated for average and worst case scenarios of human exposure from indoor sources. For toddlers, this resulted in average intakes of ∑ ionic PFCs of 4.9 ng/day (0.33 ng/kg_bw/day for a 15 kg toddlers) and ∑ neutral PFCs of 0.072 ng/day (0.005 ng/kg_bw/day) from house dust. For adults, the average daily intakes of dust were 3.6 and 0.053 ng/day (0.05 and 0.001 ng/kg_bw/day for a 70 kg adult) for ∑ ionic and ∑ neutral PFCs, respectively. The average daily inhalation of ∑ neutral PFCs was estimated to be 0.9 and 1.3 ng/day (0.06 and 0.02 ng/kg_bw/day) for toddlers and adults, respectively. For PFOS, the main ionic PFC detected in indoor air samples, the median intakes (based on those samples where PFOS was detected), resulted in indoor exposures of 0.06 and 0.11 ng/day (0.004 and 0.002 ng/kg_bw/day) for toddlers and adults, respectively. Based on previous studies on dietary intake and drinking water consumption, both house dust and indoor air contribute significantly less to PFC exposure within this population.     

Explosion hazards related to hydrogen releases in nuclear facilities

Hydrogen explosion risk needs to be carefully assessed and evaluated in nuclear facilities because of the potential catastrophic consequences: breakdown of safety equipments, failure of containment, dissemination of radioactive materials in the environment.When studying an indoor release, one possible simplification is to assume a perfect gas mixing inside the room. This assumption is effectively often used to evaluate toxic risks in the environment outside a building (Mastellone, Ponte, & Arena, 2003). However, perfect gas mixing assumption is only a rough approximation, as indoor concentrations can largely differ from mean values, due to buoyancy, recirculation zones or obstacles for example.In order to better evaluate the risk of explosion in case of an accidental release of hydrogen, IRSN conducted a numerical study using FLACS CFD software. Several parameters have been studied to identify dangerous situations and draw a representative picture of the risk: room size, position and direction of hydrogen leak, ventilation characteristics. Hydrogen release flow rates used for numerical simulations have been chosen as the highest leak rate which, by applying the assumption of perfect mixing, produces an average concentration in the room equal to hydrogen lower flammability limit (LFL).Simulation results indicate that in some particular configurations, especially for impinging hydrogen jets, hydrogen concentrations can locally be above LFL and then create explosive atmospheres with significant volumes.