Real-time molecular characterization of air pollutants in a Hong Kong residence: Implication of indoor source emissions and heterogeneous chemistry

Due to the high health risks associated with indoor air pollutants and long-term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor-to-outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle-phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5-dimethylfuran, stigmasterol, iso-/anteiso-alkanes, and fructose isomers for smoking, C₂₈-C₃₄ even n-alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality.     

Significant OH production under surface cleaning and air cleaning conditions: Impact on indoor air quality

We report measurements of hydroxyl (OH) and hydroperoxy (HO₂) radicals made by laser‐induced fluorescence spectroscopy in a computer classroom (i) in the absence of indoor activities (ii) during desk cleaning with a limonene‐containing cleaner (iii) during operation of a commercially available “air cleaning” device. In the unmanipulated environment, the one‐minute averaged OH concentration remained close to or below the limit of detection (6.5×10⁵ molecule cm^?3), whilst that of HO₂ was 1.3×10⁷ molecule cm^?3. These concentrations increased to ~4×10⁶ and 4×10⁸ molecule cm^?3, respectively during desk cleaning. During operation of the air cleaning device, OH and HO₂ concentrations reached ~2×10⁷ and ~6×10⁸ molecule cm^?3 respectively. The potential of these OH concentrations to initiate chemical processing is explored using a detailed chemical model for indoor air (the INDCM). The model can reproduce the measured OH and HO₂ concentrations to within 50% and often within a few % and demonstrates that the resulting secondary chemistry varies with the cleaning activity. Whilst terpene reaction products dominate the product composition following surface cleaning, those from aromatics and other VOCs are much more important during the use of the air cleaning device.     

常用电器对室内空气品质的影响

针对常用电器对室内空气品质的危害,分析了常用电器对室内空气品质的影响,提出了改善常用电器对室内空气品质影响的措施,有助于增加人们对常用电器与室内空气品质关系的认识,以帮助人们更好地保护室内空气品质。     

Growth of organic films on indoor surfaces

We present a model for the growth of organic films on impermeable indoor surfaces. The model couples transport through a gas‐side boundary layer adjacent to the surface with equilibrium partitioning of semivolatile organic compounds (SVOCs) between the gas phase and the surface film. Model predictions indicate that film growth would primarily be influenced by the gas‐phase concentration of SVOCs with octanol‐air partitioning (K_oa) values in the approximate range 10≤log K_oa≤13. Within the relevant range, SVOCs with lower values will equilibrate with the surface film more rapidly. Over time, the film becomes relatively enriched in species with higher log K_oa values, while the proportion of gas‐phase SVOCs not in equilibrium with the film decreases. Given stable airborne SVOC concentrations, films grow at faster rates initially and then subsequently diminish to an almost steady growth rate. Once an SVOC is equilibrated with the film, its mass per unit film volume remains constant, while its mass per unit area increases in proportion to overall film thickness. The predictions of the conceptual model and its mathematical embodiment are generally consistent with results reported in the peer‐reviewed literature.     

人群散发对高校教室室内TVOC浓度动态影响的实测分析

随机选取南京某高校10间在室人员密集的教室,在其使用期间对室内总挥发性有机化合物(TVOC)和CO₂浓度、温湿度,以及室内人员数量和典型活动状况(如开关门窗)等进行了连续监测和对比分析。研究结果表明:冬、春、夏季测试教室室内TVOC质量浓度分别为(363.1±121.7),(218.4±11.5),(583.3±38.9)μg/m³;室内TVOC浓度变化与CO₂类似,总体呈现先上升后下降的趋势,并与室内人员数量变化呈强正相关性;室内TVOC浓度水平存在季节性差异。室内总源强度的估算结果表明,室内不同样本数量的人群散发强度与室内TVOC浓度变化类似,随着人数变化,呈现出先逐渐增大,然后趋于相对稳定,最后逐渐减小的趋势。     

Perceived indoor air quality in naturally ventilated primary schools in the UK: Impact of environmental variables and thermal sensation

Indoor air quality (IAQ) in classrooms has a significant impact on children's academic performance, health, and well-being; therefore, understanding children's perception of IAQ is vital. This study investigates how children's perception of IAQ is affected by environmental variables and thermal sensation. In total, 29 naturally ventilated classrooms in eight UK primary schools were selected and 805 children were surveyed during non-heating and heating seasons. Results show that air sensation votes (ASVs) are more correlated to CO₂ levels than to operative temperatures (T_op) during non-heating seasons and more correlated to T_op than CO₂ levels during heating seasons. The impact of T_op on ASVs decreases with an increase in CO₂ levels, and the effect of CO₂ levels on ASVs decreases with increase in T_op. The most favorable ASVs are given when children feel “cool” and have “as it is” preference. By keeping CO₂ < 1000 ppm and T_op within children's thermal comfort band, ASVs are improved by 43%. The study recommends that standards should consider the impact of both temperature and CO₂ levels on perceived IAQ. Perception of IAQ also affects children's overall comfort and tiredness levels; however, this influence is more significant on tiredness level than that on overall comfort level.     

Impact of the spectral and spatial properties of natural light on indoor gas‐phase chemistry: Experimental and modeling study

The characteristics of indoor light (intensity, spectral, spatial distribution) originating from outdoors have been studied using experimental and modeling tools. They are influenced by many parameters such as building location, meteorological conditions, and the type of window. They have a direct impact on indoor air quality through a change in chemical processes by varying the photolysis rates of indoor pollutants. Transmittances of different windows have been measured and exhibit different wavelength cutoffs, thus influencing the potential of different species to be photolysed. The spectral distribution of light entering indoors through the windows was measured under different conditions and was found to be weakly dependent on the time of day for indirect cloudy, direct sunshine, partly cloudy conditions contrary to the light intensity, in agreement with calculations of the transmittance as a function of the zenithal angle and the calculated outdoor spectral distribution. The same conclusion can be drawn concerning the position within the room. The impact of these light characteristics on the indoor chemistry has been studied using the INCA‐Indoor model by considering the variation in the photolysis rates of key indoor species. Depending on the conditions, photolysis processes can lead to a significant production of radicals and secondary species.     

Effects of indoor environmental parameters related to building heating,ventilation, and air conditioning systems on patients' medical outcomes: A review of scientific research on hospital buildings

The indoor environment of a mechanically ventilated hospital building controls infection rates as well as influences patients’ healing processes and overall medical outcomes. This review covers the scientific research that has assessed patients’ medical outcomes concerning at least one indoor environmental parameter related to building heating, ventilation, and air conditioning (HVAC) systems, such as indoor air temperature, relative humidity, and indoor air ventilation parameters. Research related to the naturally ventilated hospital buildings was outside the scope of this review article. After 1998, a total of 899 papers were identified that fit the inclusion criteria of this study. Of these, 176 papers have been included in this review to understand the relationship between the health outcomes of a patient and the indoor environment of a mechanically ventilated hospital building. The purpose of this literature review was to summarize how indoor environmental parameters related to mechanical ventilation systems of a hospital building are impacting patients. This review suggests that there is a need for future interdisciplinary collaborative research to quantify the optimum range for HVAC parameters considering airborne exposures and patients’ positive medical outcomes.     

Combined use of an electrostatic precipitator and a high‐efficiency particulate air filter in building ventilation systems: Effects on cardiorespiratory health indicators in healthy adults

High‐efficiency particulate air (HEPA) filtration in combination with an electrostatic precipitator (ESP) can be a cost‐effective approach to reducing indoor particulate exposure, but ESPs produce ozone. The health effect of combined ESP‐HEPA filtration has not been examined. We conducted an intervention study in 89 volunteers. At baseline, the air‐handling units of offices and residences for all subjects were comprised of coarse, ESP, and HEPA filtration. During the 5‐week long intervention, the subjects were split into 2 groups, 1 with just the ESP removed and the other with both the ESP and HEPA removed. Each subject was measured for cardiopulmonary risk indicators once at baseline, twice during the intervention, and once 2 weeks after baseline conditions were restored. Measured indoor and outdoor PM_2.5 and ozone concentrations, coupled with time‐activity data, were used to calculate exposures. Removal of HEPA filters increased 24‐hour mean PM_2.5 exposure by 38 (95% CI: 31, 45) μg/m³. Removal of ESPs decreased 24‐hour mean ozone exposure by 2.2 (2.0, 2.5) ppb. No biomarkers were significantly associated with HEPA filter removal. In contrast, ESP removal was associated with a ?16.1% (?21.5%, ?10.4%) change in plasma‐soluble P‐selectin and a ?3.0% (?5.1%, ?0.8%) change in systolic blood pressure, suggesting reduced cardiovascular risks.     

Impact of asthma,exposure period,and filters on human responses during exposures to ozone and its initiated chemistry products

The impact of asthma, exposure period, and filter condition downstream of the mixing box of air‐conditioning system on building occupants' perceptual response, work performance, and salivary α‐amylase secretion during exposures to ozone and its initiated chemistry products is studied. The experiments were conducted in a field environmental chamber (FEC) (240 m³) simulating an office environment. Experiments were conducted during periods when the air‐handling system operated with new or used pleated panel filters at constant recirculation (7/h) and ventilation (1/h) rates. Average ozone and secondary organic aerosols (ozone‐initiated chemistry products) measured during non‐asthmatic and asthmatic subjects' 3‐h exposures in the FEC were in the ranges approximately 20–37 ppb and approximately 1.6–3 μg/m³, respectively. Asthmatic subjects' perceived odor intensity and sensory (eye, nose, and throat) irritation ratings were generally lower than those of non‐asthmatic subjects, possibly explaining why asthmatic subjects accept perceived air quality more than non‐asthmatic subjects. However, asthmatic subjects' perceived physiological‐like symptom ratings (flu, chest tightness, and headache) and concentrations of secreted salivary α‐amylase were generally higher than those of non‐asthmatic subjects. Asthmatic subjects had significantly lower accuracy than non‐asthmatic subjects in a task that required higher concentration although they had higher work speed. Filter condition did not make any significant difference for subjects' responses.     

Indoor air problems and experiences of injustice in the workplace: A quantitative and a qualitative study

This study explores subjective injustice experiences of individuals suffering from suspected or observed indoor air problems in their workplaces in two studies. We focus on injustice experiences because they influence how individuals cope with and recover from health problems. The first study reports associations between the perceived harmfulness of the indoor environment (ie, mold/inadequate ventilation) and subjective injustice experiences in workplaces in a representative sample of Finnish working‐aged people (N = 4633). Altogether, 37% of the respondents perceived their workplaces’ indoor environments to be harmful. Multivariate logistic regression analyses revealed that the risks of reporting subjective injustice experiences (eg, information, attitudes, and remuneration) were significantly higher for those reporting harmful indoor environments compared to those who reported no such problems (OR 1.28‐1.95 for different situations). The second study explored injustice experiences more closely by qualitatively analyzing the content of 23 essays. These essays were written by people who suffered from suspected or observed indoor air problems in their workplaces. The respondents reported multidimensional experiences of injustice, which related to conflicts, and moral exclusions. Awareness of these psychosocial effects is important for the prevention of unnecessary escalation of psychosocial problems in workplaces with observed and suspected indoor air problems.     

水冷式表冷器传热研究（2）：以等价干工况为理论基础的试验方法

指出了目前表冷器试验方法中因含有析湿因数项而存在的缺陷,提出了以等价干工况为基础,只做湿工况变风量、干工况变风量和变水量试验的新方法。认为新方法遵循了焓差是湿工况下换热推动力的规律试验,试验工作量减少一半以上,对试验装置的要求降低,由试验数据整理出的公式用于表冷器热力计算完全可以满足空调常用范围内的要求。     

Size-resolved dynamics of indoor and outdoor fluorescent biological aerosol particles in a bedroom: A one-month case study in Singapore

This study evaluated the interrelations between indoor and outdoor bioaerosols in a bedroom under a living condition. Two wideband integrated bioaerosol sensors were utilized to measure indoor and outdoor particulate matter (PM) and fluorescent biological airborne particles (FBAPs), which were within a size range of 0.5-20 μm. Throughout this one-month case study, the median proportion of FBAPs in PM by number was 19% (5%; the interquartile range, hereafter) and 17% (3%) for indoors and outdoors, respectively, and those by mass were 78% (12%) and 55% (9%). According to the size-resolved data, FBAPs dominated above 2 and 3.5 μm indoors and outdoors, respectively. Comparing indoor upon outdoor ratios among occupancy and window conditions, the indoor FBAPs larger than 3.16 μm were dominated by indoor sources, while non-FBAPs were mainly from outdoors. The occupant dominated the indoor source of both FBAPs and non-FBAPs. Under awake and asleep, count- and mass-based mean emission rates were 45.9 and 18.7 × 10⁶ #/h and 5.02 and 2.83 mg/h, respectively. Based on indoor activities and local outdoor air quality in Singapore, this study recommended opening the window when awake and closing it during sleep to lower indoor bioaerosol exposure.     

Real-time air monitoring of occupational exposures to particulate matter among hairdressers in Maryland: A pilot study

Hairdressers are exposed to particulate matter (PM), a known air pollutant linked to adverse health effects. Still, studies on occupational PM exposures in hair salons are sparse. We characterized indoor air PM concentrations in three salons primarily serving an African/African American (AA) clientele, and three Dominican salons primarily serving a Latino clientele. We also assessed the performance of low-cost sensors (uRAD, Flow, AirVisual) by comparing them to high-end sensors (DustTrak) to conduct air monitoring in each salon over 3 days to quantify work shift concentrations of PM_2.5, respirable PM (RPM), and PM₁₀. We observed high spatial and temporal variability in 30-min time-weighted average (TWA) RPM concentrations (0.18–5518 μg/m³). Readings for the uRAD and AirVisual sensors were highly correlated with the DustTrak (R² = 0.90–0.99). RPM 8-hour TWAs ranged from 18 to 383 µg/m³ for AA salons, and 9–2115 µg/m³ for Dominican salons. Upper 95th percentiles of daily RPM exposures ranged from 439 to 2669 µg/m³. The overall range of 30-min TWA PM_2.5 and PM₁₀ concentrations was 0.13–5497 and 0.36-,541 μg/m³, respectively. Findings suggest that hairdressers could be overexposed to RPM during an 8-hour shift. Additional comprehensive monitoring studies are warranted to further characterize temporal and spatial variability of PM exposures in this understudied occupational population.     

水冷式表冷器传热研究(6):机器露点表达式的建立

建立了水冷式表冷器冷盘管表面平均热状态在干工况和湿工况下的数学表达式，通过理论和实验分析了各影响因素及影响程度。指出结构特性一定的表冷器，干工况下冷盘管表面平均热状态温度和进风干球温度、冷水初湿成线性关系；湿工况下在空调常用范围内，冷盘管表面平均热状态焓值和进风焓值，冷水初温成线性关系，且两种工况下冷盘管表面平均热状态温度（或焓值）都随迎面风速增大而增大，随水流速增大而减小。