Model Estimates of the Contributions of Environmental Tobacco Smoke to Volatile Organic Compound Exposures in Office Buildings

Volatile organic compounds (VOC) in office buildings originate from multiple sources, such as outdoor air, building materials., occupants, office supplies, and office equipment. Many of the VOC found in office buildings are also present in environmental tobacco smoke (ETS), e.g., benzene, toluene, formaldehyde. Measurements made to date in office buildings have been interpreted by some to imply that the contributions of ETS to VOC exposures in office buildings are small. We have made a first order estimate of the contributions of ETS to VOC concentrations based on the VOC content of ETS and a time-dependent mass-balance model. Four different ventilation-infiltration scenarios were modelled for a typical office building. The results indicate that ETS can contribute significantly to total indoor levels of VOC in office buildings, even under moderate ventilation conditions. Ranges of concentrations for three of the four modelled scenarios substantially overlapped measured ranges of the compounds in office buildings. Average daytime concentrations of benzene from ETS, for example, for three of the four modelled scenarios, ranged from 2.7 to 6.2 μg m^?3, compared to reported measurements of 1.4 to 8.1 μg m^?3 for four office buildings. Under a “worst reasonable” case scenario, the average modelled ETS-contributed concentration of benzene was 33.9 μg m^?3 for a 40-hour work week.     

Indoor Climate and Indoor Air Quality in Residential Buildings

In buildings which were built within the last 15 to 20 years, or which have been retrofitted, and which do notfeature a mechanical ventilation system, air changes between 0.01 h^?1 and 0.5 h^?1 were measured while windows were closed. In the bedrooms of such buildings, when doors and windows were closed, CO₂ concentrations of up to 4300 ppm were measured whereby the 1500 ppm limit was often exceeded. Simulation calculations and diverse measurements using different door positions with simultaneously closed windows have shown that with the door open more than 10 cm, and a minimal air exchange in the whole of an apartment of 0.1 h^?1, a CO₂ concentration of I500 ppm was not or was only insignifiantly exceeded even after 10 hours. Investigations in a dwelling fined with a mechanical ventilation system have shown that air quality and the indoor climate parameters were in an optimal range.     

Impact of Temperature and Humidity on Perception of Indoor Air Quality During Immediate and Longer Whole-Body Exposures

Abstract Acceptability of clean air and air polluted by building materials was studied in climate chambers with different levels of air temperature and humidity in the ranges 18–28°C and 30-70% relative humidity (RH). The acceptability of the air quality immediately after entering a chamber and during the following 20-min whole-body exposure was assessed by 36 untrained subjects who maintained thermal neutrality by modifying their clothing. The results confirm the significant decrement of the acceptability with increasing temperature and humidity, as shown in a previous study with facial exposures. The odour intensity was found to be independent of temperature and humidity. A linear relation between acceptability and enthalpy of air was again observed by this experiment. No significant difference was observed between the immediate acceptability and the acceptability during the following 20-min exposure, i.e., no adaptation took place. Both the immediate assessment of acceptability and the assessments during the 20-min exposure were independent of the air temperature and humidity to which the subjects were exposed before entering the chamber. The results further indicate that a notable decrement of the ventilation requirement may be achieved by maintaining a moderate enthalpy of air in spaces.     

Impact of Temperature and Humidity on the Perception of Indoor Air Quality

Abstract Sensory responses to clean air and air polluted by five building materials under different combinations of temperature and humidity in the ranges 18-28°C and 30-70%RH were studied in the laboratory. A specially designed test system was built and a set of experiments was designed to observe separately the impact of temperature and humidity on the perception of air quality/odour intensity, and on the emission of pollutants from the materials. This paper reports on the impact on perception. The odour intensity of air did not change significantly with temperature and humidity; however, a strong and significant impact of temperature and humidity on the perception of air quality was found. The air was perceived as less acceptable with increasing temperature and humidity. This impact decreased with an increasing level of air pollution. Significant linear correlations were found between acceptability and enthalpy of the air at all pollution levels tested, and a linear model was established to describe the dependence of perceived air quality on temperature and humidity at different pollution levels.     

Indoor Air Quality in Renovated Dutch Homes

The indoor air quality in several types of dwellings that were renovated to save energy for spatial heating has been investigated. Concentrations of pollutants were monitored in three rooms of inhabited houses. Data of the outside air and ventilation and infiltration were also collected. Relationships were established between observed concentrations and ventilation. In some cases concentrations show a good relationship with the calculated air change rate, in other cases this relationship was poor or absent. Elevated levels of pollutants could be related to sources in most cases. The ventilation behavior of the inhabitants has a major influence on the concentrations. From this and other studies it can be concluded that, in general, making dwellings more airtight leads to higher concentrations of pollutants. Deviations from health-related guidelines then become more likely.     

European Indoor Air Quality Audit Project in 56 Office Buildings

Abstract A European project started at the end of 1992, in which, in addition to current methods, trained sensory panels were used to investigate office buildings all over Europe. The main aim of this EC-Audit was to develop assessment procedures and guidance on ventilation and source control, to help optimize energy use in buildings while assuring good indoor air quality. In each of nine countries, six or more office buildings were selected. Measurements were performed at five selected locations in each building. The buildings were studied while normally occupied and ventilated to identify the pollution sources in the spaces and to quantify the total pollution load caused by the occupants and their activities, as well as the ventilation systems. The investigation included physical and chemical measurements, assessment of the perceived air quality in the spaces by a trained sensory panel, and measurement of the outdoor air supply to the spaces. A questionnaire for evaluating retrospective and immediate symptoms and perceptions was given to the occupants of the buildings. The building characteristics were described by use of a check-list. The annual energy consumption of the buildings and the weather conditions were registered. This paper presents results and conclusions of the audit in 56 buildings in Europe. However, the analysis and discussions of the results are a summary of the work done, and are focused mainly on comparison between sensory assessments and the other measurements performed. Furthermore, this paper brings the results of the study based on a two-factor analysis. A paper dealing with results on a multifactorial analysis is in preparation.     

绿色建筑室内空气质量测评技术探讨

通过研究现有国家和行业标准中涉及的室内空气质量指标参数和测评方法,从绿色建筑评价要求出发,本着经济性、实用性和可操作性原则,综合比较了各指标参数测评方法的优缺点,给出了简便易行的、适用于绿色建筑室内空气质量的测评方法,为今后进行绿色建筑室内空气质量测评提供依据和参考。     

The Po River Delta (North Italy) Indoor Epidemiological Study: Home Characteristics,Indoor Pollutants,and Subjects' Daily Activity Pattern

Abstract A total of 140 homes in the Po River Delta area of North Italy (near Venice) were monitored during summer and winter to measure the concentration of nitrogen dioxide (NO₂), and respirable suspended particulate matter (RSP, ≤ 2.5 μm). In this paper, the findings on home characteristics, daily activity pattern of occupants, and residential indoor air quality are described. Our study confirms that people spend the greater part of their daily lives indoors (84%), especially at home (64%). The concentration of monitored pollutants was greater in winter than in summer. The highest levels of NO₂ were found in the kitchens. Significantly higher indoor NO₂ levels were found in the houses with gas-furnace heating and/or with gas water heater located inside the home. RSP was significantly higher in homes where tobacco smoking took place, and was significantly related to the number of cigarettes smoked. A significant relationship between NO₂ indoor concentrations and RSP values in both seasons was found.     

Outdoor Air Contaminants and Indoor Air Quality under Transient Conditions

The indoor concentrations of contaminants originating from outdoor sources have been measured and calculated under transient conditions. The results show that contaminants that are supplied to an office building via the ventilation system can reach considerably high concentration levels. The indoor/outdoor concentration ratio and time lag are dependent on the air change rate. In buildings with low air change rates the indoor concentration variations are smoothed out compared to buildings with high air change rates. The results from the theoretical model are compared to the results from both laboratory and field measurements and the model is verified for well mixed conditions in a 20 m³ test chamber. The model can be used to simulate different control strategies for reduction of indoor contaminant concentrations related to outdoor sources. One such control strategy is based on reduction of the outdoor air change rate during periods with peak outdoor contaminant concentrations.     

Influence of relative humidity and gaseous ammonia on the nicotine sorption to indoor materials

Sorption of nitrogen-containing organic constituents of environmental tobacco smoke may be influenced by ammonia, a common indoor gas, and relative humidity (RH). We quantified sorption kinetics and equilibria of nicotine with stainless steel, cotton-polyester curtain, and polypropylene carpet at 0%, 50%, and 90% RH and in the presence of ammonia using a 10-l stainless steel chamber. Nicotine was introduced into the chamber by flash evaporating 50 μl of pure liquid. Kinetic sorption parameters were determined by fitting a mass balance model to experimental results using a nonlinear regression. Results show that an equilibrium partition coefficient, k(e) , of nicotine tended to increase as the RH increased for the curtain and carpet. Adsorbed water may contribute to an increase in available sites for nicotine sorption on the surface. In the presence of 20- and 40-ppm NH(3) , the values of k(e) for carpet were decreased by 14-40% at 50% and 90% RH, but the effect of NH(3) was not observed at 0% RH. The values of k(e) ranged from 54 to 152 m. Our findings indicate the relative importance of nicotine sorption to surfaces is dependent on the relative humidity and the presence of ammonia. PRACTICAL IMPLICATIONS: This research demonstrates that relative humidity and gaseous ammonia can influence nicotine sorption to common indoor surfaces, i.e., curtains and carpets. Increasing the relative humidity from dry to modest appears to enhance the sorptive capacity. Presence of the typical range of gaseous ammonia concentrations can reduce the nicotine sorption in a humid environment but does not affect the sorptive capacity in the absence of added water. Thus, studies on the dynamic sorption of other alkaloids or amine constituents of environmental tobacco smoke to indoor surfaces should consider the impact of water vapor concentration because of the interaction of water with the surface and sorbates. Furthermore, the mixture of gaseous amines may participate in adsorption site competition.     

Ozone in Residential Air: Concentrations,I/O Ratios,Indoor Chemistry,and Exposures

Ozone concentrations were measured in indoor and outdoor residential air during the summer of 1992. Six homes located in a New Jersey suburban area were chosen for analysis, and each home was monitored for 6 days under different ventilation and indoor combustion conditions. The 5-hour average ozone concentration outdoors over the monitoring period was 95 ± 36 ppbv. One third of the days exceeded the National Ambient Air Quality Standard (NAAQS), one-hour maximum concentration of 120 ppb. The mean indoor to outdoor (I/O) ratios of ozone concentration ranged from 0.22 ± 0.09 to 0.62 ± 0.11, depending upon ventilation rate and indoor gas combustion. The presence of indoor gas combustion can significantly decrease the I/O ratio. Because of the great amount of time that people spend indoors, the indoor residential exposures were estimated to account for 57% of the total residential exposures. One type of the possible gas-phase reactions for indoor ozone, the reaction of ozone with a volatile organic compound containing unsaturated carbon-carbon bonds, is discussed with some supporting evidence provided in the study.     

Indoor Air Quality Investigations at Five Classrooms

Abstract Five classrooms, air-conditioned or naturally ventilated, at five different schools were chosen for comparison of indoor and outdoor air quality. Temperature, relative humidity (RH), carbon dioxide (CO₂), sulphur dioxide (SO₂), nitric oxide (NO), nitrogen dioxide (NO₂), particulate matter with diameter less than 10 mm (PM₁₀), formaldehyde (HCHO), and total bacteria counts were monitored at indoor and outdoor locations simultaneously. Respirable particulate matter was found to be the worst among parameters measured in this study. The indoor and outdoor average PM₁₀ concentrations exceeded the Hong Kong standards, and the maximum indoor PM₁₀ level was even at 472 μ;g/m³. Air cleaners could be used in classrooms to reduce the high PM₁₀ concentration. Indoor CO₂ concentrations often exceeded 1,000 μl/l indicating inadequate ventilation. Lowering the occupancy and increasing breaks between classes could alleviate the high CO₂ concentrations. Though the maximum indoor CO₂ level reached 5,900 μl/l during class at one of the sites, CO₂ concentrations were still at levels that pose no health threats.     

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.     

The link between symptoms of office building occupants and in-office air pollution: the Indoor Air Pollution Index

The lack of an effective indoor air quality (IAQ) metric causes communication concerns among building tenants (the public), building managers (decision-makers), and IAQ investigators (engineers). The Indoor Air Pollution Index (IAPI) is developed for office buildings to bridge this communication discord. The index, simple and easily understood, employs the range of pollutant concentrations and concentrations in the subject building to estimate a unitless single number, the IAPI, between 0 (lowest pollution level and best IAQ) and ten (highest pollution level and worst IAQ). The index provides a relative measure of indoor air pollution for office buildings and ranks office indoor air pollution relative to the index distribution of the US office building population. Furthermore, the index associates well with occupant symptoms, percentage of occupants with persistent symptoms. A tree-structured method is utilized in conjunction with the arithmetic mean as the aggregation function. The hierarchical structure of the method renders not only one index value, but also several sub-index values that are critical in the study of an office air environment. The use of the IAPI for IAQ management is illustrated with an example. The decomposition of the index leads to the ranking of sampled pollutants by their relative contribution to the index and the identification of dominant pollutant(s). This information can be applied to design an effective strategy for reducing in-office air pollution.     

Indoor Air Quality Investigation on Commercial Aircraft

Abstract Sixteen flights had been investigated for indoor air quality (IAQ) on Cathay Pacific aircraft from June 1996 to August 1997. In general, the air quality on Cathay Pacific aircraft was within relevant air quality standards because the average age of aircraft was less than 2 years. Carbon dioxide (CO₂) levels on all flights measured were below the Federal Aviation Administration (FAA) standard (30,000 ppm). The CO₂ level was substantially higher during boarding and de-boarding than cruise due to low fresh air supply. Humidity on the aircraft was low, especially for long-haul flights. Minimum humidity during cruise was below the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) minimum humidity standard (20%). The average temperature was within a comfortable temperature range of 23±2°C. The vertical temperature profile on aircraft was uniform and below the International Standard Organization (ISO) standard. Carbon monoxide levels were below the FAA standard (50 ppm). Trace amount of ozone detected ranged from undetectable to 90 ppb, which was below the FAA standard. Particulate level was low for most non-smoking flights, but peaks were observed during boarding and de-boarding. The average particulate level in smoking flights (138 (ig/m3) was higher than non-smoking flights (7.6 μg/m³). The impact on IAQ by switching from low-mode to high-mode ventilation showed a reduction in CO₂ levels, temperature, and relative humidity.     

Indoor air quality in Portuguese schools: levels and sources of pollutants

Indoor air quality (IAQ) parameters in 73 primary classrooms in Porto were examined for the purpose of assessing levels of volatile organic compounds (VOCs), aldehydes, particulate matter, ventilation rates and bioaerosols within and between schools, and potential sources. Levels of VOCs, aldehydes, PM_2.5, PM₁₀, bacteria and fungi, carbon dioxide (CO₂), carbon monoxide, temperature and relative humidity were measured indoors and outdoors and a walkthrough survey was performed concurrently. Ventilation rates were derived from CO₂ and occupancy data. Concentrations of CO₂ exceeding 1000 ppm were often encountered, indicating poor ventilation. Most VOCs had low concentrations (median of individual species <5 μg/m³) and were below the respective WHO guidelines. Concentrations of particulate matter and culturable bacteria were frequently higher than guidelines/reference values. The variability of VOCs, aldehydes, bioaerosol concentrations, and CO₂ levels between schools exceeded the variability within schools. These findings indicate that IAQ problems may persist in classrooms where pollutant sources exist and classrooms are poorly ventilated; source control strategies (related to building location, occupant behavior, maintenance/cleaning activities) are deemed to be the most reliable for the prevention of adverse health consequences in children in schools.     

Relationships Between Ventilation and Indoor Air Quality: A Review

Abstract Adjustment of ventilation rates in buildings is widely practised, both to provide good air quality on a proactive basis and to mitigate air quality problems associated with occupant complaints. However, both cross-sectional and experimental epidemiological studies have reported mixed results and have for the most part failed to establish definitive relationships between ventilation rates and symptom prevalence or dissatisfaction with air quality. The difficulties involved in establishing such relationships may be due to a variety of confounding factors which include limitations in study design and interaction effects; difficulties in controlling ventilation rates in experimental studies; inadequate mixing of supply air in occupied spaces; high source strengths for some contaminants; dynamic interactions between sources and ventilation rates that result in increased contaminant emissions; contaminant dose-response sensory effects which are log-linear; potential contaminant generation within ventilation systems themselves; and multifactorial genesis of sick building symptoms. There is limited evidence to suggest that ventilation rate increases up to 10 L/s person may be effective in reducing symptom prevalence and occupant dissatisfaction with air quality and that higher ventilation rates are not effective. Because of complex relationships between ventilation rates, contaminant levels, and building-related health complaints/dissatisfaction with air quality, the use of ventilation as a mitigation measure for air quality problems should be tempered with an understanding of factors which may limit its effectiveness.     

Cleaning for Improved Indoor Air Quality: an Initial Assessment of Effectiveness

Abstract A study was conducted to characterize the indoor environment of a multifloor, multiuse, nonproblem, noncompliant building through long-term monitoring for biological, chemical, and particulate pollutants. The study also assessed the effects of cleaning on indoor air quality by providing a program to monitor baseline levels, providing a rigorous (deep) cleaning of the building, and then continuing to monitor after implementation of a standardized, improved, cleaning program. To assess the effectiveness of the cleaning program, air, surface, and dust data from monitoring prior to the cleaning program were compared with those obtained while the improved housekeeping program was in place. Correlations between pollutants and other environmental factors were studied. The data suggest that the improved cleaning program contributed to indoor air quality through the reduction of airborne dust mass, total volatile organic compounds, and culturable bacteria and fungi.