室内空气中TVOC浓度检测准确性影响因素的探讨

针对<民用建筑工程室内环境污染控制规范>GB50325-2001(2006版)使用中存在的一些问题,从采样过程和热解析过程,对热解析气相色谱法检测室内空气中TVOC浓度的影响因素进行分析,并对有关问题进行了探讨.     

建筑室内总挥发性有机物成分分析及其对室内空气质量影响

总挥发性有机物是判断室内空气质量的重要指标,在我国《民用建筑工程室内环境污染控制规范》(GB 50325-2001)标准中属于必测的指标。国家标准样品中共含有苯、甲苯、乙酸丁酯等9种物质,而由于其中实际成分权重的问题,导致在实际测试中可能出现由于某种污染物(如乙酸丁酯)毒性较小,但是权重较大,从而使总挥发性有机物接近或超出国家标准;某种污染物毒性较大(如苯),但是权重较小,反而不会超出国家标准。这使判断室内空气质量对人员的影响出现较大的问题。本文通过对实际测试的大量样本的详细分析,发现有些空气样本中乙酸丁酯含量较多,但其毒性较小,故对人的影响远远小于苯系物含量较小的总挥发性有机物。因此,需要进行大量室内污染物现场调研工作,从而对目前国家标准中规定的污染物比例等做出修正。     

空调房间3种侧送风方式下室内气流组织的数值模拟与分析

采用雷诺时均的Navier-Stokes方程与标准κ-ε双方程模型,对常用的3种侧送风方式下的办公建筑进行数值模拟,对室内空气的速度场、温度场以及空气龄进行分析,认为送回风同侧的通风方式优于送回风对侧的通风方式,可获得较高的室内空气品质。     

Modelling of Emission and Re-emission of Volatile Organic Compounds from Building Materials with Indoor Air Applications

Polymer materials and their additives are today ever present in our daily surroundings. These materials have been found to emit a number of different volatile organic compounds (VOCs) into the ambient air, thus affecting the quality of the indoor air VOCs with detectable concentrations are exchanged between the different materials and indoor air. Materials present in the system act as sorbents as well as sources of emission, depending on the concentration of the VOCs in the air at a specific time. This work demonstrates a method of studying the phenomena of absorption/re-emission. A hypothetical room that resembles a furnished office has been studied. A PVC flooring material was used as a primary emission source in a system where materials such as wood, paint, cloth, chipboard, and cellulose were present. Mass transfer in the solid materials was assumed to be by diffusion. The results show that the mechanism of absorption/re-emission of volatiles may extend the time of residence in an indoor system considerably. A person working in this environment could risk longer exposure to toxic volatiles than if there were no absorption/re-emission effects.     

A Review and a Limited Comparison of Methods for Measuring Total Volatile Organic Compounds in Indoor Air

Numerous methods attempt to measure the combined concentrations of volatile organic compounds (VOCs) in indoor air as total VOCs (TVOC). This paper reviews TVOC methods recently presented in the literature and at an international conference on indoor air quality, for the purpose of identifying common practices and of assessing the impacts that choices of sample collection media and analytical methods and instrumentation can have on TVOC results. The paper also presents the results of laboratory and field comparisons of three TVOC methods. These are a flame-ionization-detector (FID) method, a gas chromatography/mass spectrometry (GC/MS) method, and a method employing a photoacoustic infrared (IR) gas monitor. The laboratory experiments were conducted with eight different mixtures of VOCs. The FID method demonstrated an average accuracy of 93 ± 18 percent when the measured values were calculated as concentrations of carbon. The FID and GC/MS methods demonstrated average accuracies of 77±37 and 75±22 percent, respectively, when the measured hydrocarbon-equivalent values were compared to the expected mass concentrations of the mixtures. The higher uncertainty for the FID was largely due to the low mass response of 27 percent for chlorinated compounds. The response of the IR gas monitor varied between 6 and 560 percent for different classes of compounds. Air samples from ten buildings were analyzed by both the FID and GC/MS methods. The results were highly correlated and similar, with the GC/MS values approximately 20 percent higher on average.     

The Influence of Office Furniture,Workstation Layouts,Diffuser Types and Location on Indoor Air Quality and Thermal Comfort Conditions at Workstations

Abstract Many factors affect the airflow patterns, contaminant removal efficiency and the indoor air quality at individual workstations in office buildings. The effects of office furniture design and workstation layouts on ventilation performance, contaminant removal efficiency and thermal comfort conditions at workstations were studied. The range of furniture configurations and environmental parameters investigated included: 1) partition heights, 2) partition gap size, 3) diffuser types, 4) supply air diffuser location relative to the workstation, 5) return air grill location relative to the workstation, 6) heat source locations, 7) presence of furniture, 8) supply air temperatures, 9) adjacent workstations, 10) contaminant source locations, 11) supply air flow rates, and 12) outdoor air flow rates. The tracer gas technique was used to study experimentally the relative impact of these parameters on the air distribution and ventilation performance, as well as contaminant removal efficiency. Thermal environmental parameters such as air velocity and temperature were monitored at several locations to characterize the impact of these parameters on the thermal comfort conditions. The results showed that the outdoor air flow rate had a significant influence on the mean age of air. The air distributions at all the workstations were good even when the supply air flow rate was relatively low (i.e 5 L/s). At the same time, most of the parameters tested had a significant influence on contaminant removal efficiency when there was a contaminant source present somewhere in the office.     

Interpretation and Limitations of the Concept “Total Volatile Organic Compounds” (TVOC) as an Indicator of Human Responses to Exposures of Volatile Organic Compounds (VOC) in Indoor Air

The TVOC summation of masses of non-reactive substances has often been used as a practical way of reporting environmental measurements of volatile organic compounds. This total concentration, moreover, is often used as an indication of the potential of a multiomponent atmospheric pollution with substances of low chemical reactivity to cause chemically induced sensory irritation. This use of the TVOC indicator has never been standardized. Various authors have used different measuring techniques and the results have been used to predict certain types of health effect. This article discusses the toxicological background for the TVOC concept in relation to nonspecific sensory irritation and identifies some theoretical limitations in its use within this context. The TVOC indicator of nonspecific sensory irritations should be based only on a limited range of compounds and should be interpreted as a lower limit of the possible intensity of sensory irritation. Based on the discussions, some precautions are recommended with respect to measurements of TVOC and interpretation of the measurements.     

Indoor air quality and energy performance of air-conditioned office buildings in Singapore

An integrated indoor air quality (IAQ)-energy audit methodology has been developed in this study in Singapore, which provides a rigorous and systematic method of obtaining the status-quo assessment of an 'IAQ signature' in a building. The methodology entails a multi-disciplinary model in obtaining measured data pertaining to different dimensions within the built environment such as the physical, chemical, biological, ventilation, and occupant response characteristics. This paper describes the audit methodology and presents the findings from five air-conditioned office buildings in Singapore. The research has also led to the development of an indoor pollutant standard index (IPSI), which is discussed in this paper. Other performance indicators such as, the ventilation index and the energy index as well as the building symptom index (BSI) are also presented and discussed in the context of an integrated approach to IAQ and energy. Several correlation attempts were made on the various symptoms, indoor air acceptability, thermal comfort, BSI and IPSI, and while BSI values are found to correlate among them as well as with IAQ and THERMAL COMFORT acceptability, no such correlation was observed between BSI and IPSI. This would suggest that the occupants' perception of symptoms experienced as well as environmental acceptability is quite distinct from IAQ acceptability determined from empirical measurements of indoor pollutants, which reinforces the complex nature of IAQ issues.     

The associations of indoor environment and psychosocial factors on the subjective evaluation of Indoor Air Quality among lower secondary school students: a multilevel analysis

Subjective evaluation of Indoor Air Quality (subjective IAQ) reflects both building‐related and psychosocial factors, but their associations have rarely been studied other than on the individual level in occupational settings and their interactions have not been assessed. Therefore, we studied whether schools’ observed indoor air problems and psychosocial factors are associated with subjective IAQ and their potential interactions. The analysis was performed with a nationwide sample (N = 195 schools/26946 students) using multilevel modeling. Two datasets were merged: (i) survey data from students, including information on schools’ psychosocial environment and subjective IAQ, and (ii) data from school principals, including information on observed indoor air problems. On the student level, school‐related stress, poor teacher–student relationship, and whether the student did not easily receive help from school personnel, were significantly associated with poor subjective IAQ. On the school level, observed indoor air problem (standardized β = ?0.43) and poor teacher–student relationship (standardized β = ?0.22) were significant predictors of poor subjective IAQ. In addition, school‐related stress was associated with poor subjective IAQ, but only in schools without observed indoor air problem (standardized β = ?0.44).     

Seasonal and Yearly Patterns of Indoor Nitrogen Dioxide Levels: Data from Albuquerque,New Mexico

There are few data sets appropriate for characterizing the indoor concentrations of air pollutants over the long term. An understanding of the variability in indoor pollutant levels is particulurly relevant to the design of epidemiologic investigations: misclassifiation of exposure due to the inaccuracy of exposure estimates tends to weaken the association of exposure with health outcome. This paper uses a series of indoor NO₂ measurements collected at two-week intervals over 18-month periods between 1988 and 1991 to describe the seasonal and year-to-year variability in indoor NO₂,. The data show that there can be large year-to-year differences in both the sample distribution of indoor NO₂ as well as the household average. For homes with gas ranges with continuously-burning pilot lights, the average bedroom NO₂ concentration was 25% higher in the winter of 1990-1991 than in the winter of 1989-1990 but only 4% higher during the winter of 1988-1989 than during the winter of 1989-1990. The winter-to-winter correlations within homes ranged from a low of 0.53 to a high of 0.88. The year-to-year differences in mean indoor concentrations were not related to temperature patterns. Occupant behaviors that influence air exchange rate and/or source use are hypothesized to be the major determinant of the observed pattern. Exposure data collected during a single year should be cautiously extrapolated to other years. However, in Albuquerque homes, the data suggest that the year-to-year variability in household NO₂ levels will not have a strong impact on classifying exposure into broad categories.     

Small Chamber Tests and Headspace Analysis of Volatile Organic Compounds Emitted from Household Products

A chamber method for the characterization of the complex composition and time dependence of volatile organic compound (VOC) emissions from household products is described and the results obtained for five household products (two liquid floor detergents, one wax, a spray detergent for carpets, and a spray polish for furniture) are reported and compared to headspace measurements. An empirical mathematical model has been used to describe the time dependence of VOC concentrations in the chamber. The model allows characterization of complex emissions and their time dependence with relatively few parameters. Significant differences in the composition of emissions determined in the chamber and in headspace air have been observed and are discussed in terms of polarity and water solubility of the emitted compounds.     

燃气输配管网结构分析的指标与分析技术

燃气输配管网的压力级制、管网型式、阀门配置和管径配置等是管网结构的内容。从管网结构的角度分析输配管网称为输配管网结构分析。列举了燃气输配管网结构分析的特性指标体系,指出结构分析的主要技术方法。     

A Study of Human Reactions to Emissions from Building Materials in Climate Chambers. Part II: VOC Measurements,Mouse Bioassay,and Decipol Evaluation in the 1–2 mg/m3 TVOC Range

Monitoring of human reactions to the emission of formaldehyde and volatile organic compounds (VOC) from four commonly used building materials was carried out. The building materials were: a painted gypsum board, a rubber floor, a nylon carpet, and a particle board with an acid-curing paint. The exposures were performed in climate chambers. The air quality was quantified on the decipol scale by a trained panel, measurements of formaldehyde and VOC being performed simultaneously. The irritating potency of the materials was measured by a mouse bioassay. The VOC measurements showed several malodorants and irritants. Some abundant VOC identified in the head-space analyses were absent in the climate chamber air. The rubber floor and the nylon carpet exhibited a marked increase in decipols compatible with a number of odorous VOC identified in the air. A high formaldehyde concentration (minimum 743μg/m³) was measured for the particle board coated with an acid-curing paint. This was not reflected by a corresponding relatively high decipol value but a long-lasting irritating potency was observed in the mouse bioassay. TVOC sampled on Tenax and expressed in mass per volume as well as in molar concentration, and decipol evaluation both have limitations and should be used with caution as indicators of (perceived) indoor air quality. Eye irritation expressed by means of the eye index reflecting the tear film quality index (comprised of break-up time, foam formation, thickness of the precorneal lipid layer of the tear film, and epithelial damage) was found to be insensitive to formaldehyde and a VOC mixture but sensitive to TVOC concentrations of 1–2 mg/m³. Lipophilic VOC may be the cause of reduced tear film quality by destabilization of the lipid multilayer of the tear film.     

关于GB 50325—2001和GB/T 18883—2002协调性的讨论

本文针对目前我国颁布的室内空气质量标准<民用建筑工程室内环境污染控制规范>(GB 50325-2001)和<室内空气质量标准>(GB/T 18883-2002),分析了标准之间和标准本身存在的不协调性,重点指出了2个标准在指标选取、指标限值、测试过程方面不统一的问题,提出了出现不协调的技术原因,并指出了如何在室内空气质量范围内避免不协调的处理方法及相对应的研究方向.     

Detection of human effluents by a MOS gas sensor in correlation to VOC quantification by GC/MS

Due to increasing interest in indoor air quality (IAQ) monitoring for demand controlled ventilation (DCV) aiming at improved perceived air quality, health, energy and cost saving, the objective of this study has been the development of a sensor module based on a single microelectromechanical-system (MEMS) metal oxide semiconductor (MOS) gas sensor for IAQ monitoring as close as possible to the human sensory impression in indoor environments. Based on the results of a statistical evaluation on human induced volatile organic compounds (VOCs) in the ambient air of indoor environments correlating with human presence and perceived air quality, the performance of differently doped SnO₂ thick film gas sensor materials has been investigated in laboratory and by means of field tests in order to find the most promising sensor material for IAQ monitoring based on the detection of changes of human induced VOCs in indoor air. Implementation of an empirical evaluation algorithm reversing proportionality of anthropogenic CO₂ production and other bio-effluent generation allows prediction of CO₂ equivalent units. Analytical instrumentation and reference sensors served to evaluate the effectiveness of the developed sensor module in real-life.     

New standards for the determination of geosmin and methylisoborneol in water by gas chromatography/mass spectrometry

Deuterium labelled geosmin and methylisoborneol (MIB) have been synthesized and evaluated as internal standards in the determination of geosmin and MIB in water by closed loop stripping followed by gas chromatography/mass spectrometry (GC/MS). The labelled standards were compared with chloroalkanes added as internal standards either at the time of sampling or immediately before closed loop stripping. When added at sampling time, the new standards enabled accurate determination of the geosmin and MIB present initially, even when the samples were analysed as much as 3 weeks later. The new standards gave better precision and accuracy than the chloroalkanes and overcame the underestimation of initial analyte concentration which usually results from losses of analyte through adsorption, volatilisation, biodegradation etc. during sample storage. Geosmin had a limit of detection of<0.1ng/l and 1 ng/lwas determined with a coefficient of variation (CV) of 1.2% (n = 5). MIB was determined at 1 ng/l with a CV of 3.5% (n = 5).