Indoor and Built Environment

Recently published studies where individual volatile organic compounds (VOCs) have been identified and quantified have been reviewed. Mean con centrations of the compounds have been calculated for public places, homes, and transportation environments. Where the data were available to differen tiate between smoking and non-smoking areas these have been summarised. Studies which have attempted to assess health impacts such as odour and irri tation in conjunction with VOCs appear to be using unrealistic mixtures and concentrations of VOCs compared to those found in real life situations. Future research employing more realistic concentrations of VOCs will aid in under standing the true effect VOCs may have on indoor air quality and the persons exposed in that environment. Research using the American Society of Testing and Materials (ASTM) animal bioassay E981-84 may provide a reasonable method for establishment of human exposure guidelines. Concentrations found to cause irritation in humans are higher than typical indoor levels found in this review. Irritation is unlikely to occur at the mean levels reported herein. In general, where ventilation rates meet or exceed the requirements of ASHRAE Standard 62-1989, Ventilation for Acceptable Indoor Air Quality, TVOC levels are low, usually less than 1 mg/m3 and concentrations of individ ual VOCs are well below (less than 1 %) any recognised occupational exposure standard.

An organic vapour concentrator with Tenax-TA as the adsorbent or a gas- sampling valve was used in combination with a transportable gas chromato graph (GC) for measurement of indoor airborne organics in the range of 5- 15,000 μg/m³. With the gas-sampling valve, detection limits were, approxi mately 50-200 and 10-100 μg/m³ with flame ionisation (FID) and photo-ion isation detectors (PID), respectively. By substituting the concentrator for the valve, detection limits were improved significantly. The detection limits, based upon a signal-to-noise ratio of 3 : 1, were approximately 2, 3 and 4 μg/m³, respectively, for toluene, α-pinene and 1,4-dichlorobenzene with an air sample of 100 ml collected with the concentrator and analysed with the GC/FID. The respective detection limits were improved by factors of 5, 6 and 8, with the PID. Instrument response was linear over the range of 2-2,000 μg/m³ with the GC/FID and 0.2-2,000 μg/m³ with the GC/PID for the test compounds. The precision of the method determined by repeat injections of a gas standard was better than 5% relative standard deviation. The instrument response factor varied by less than 15 % over a 12-day period as determined with a certified gas mixture of test compounds.

Relationships between subjective perception of indoor air quality, building characteristics, indoor exposures, and personal factors were studied in 225 female Swedish hospital workers. The prevalence of weekly complaints to do with dry air was 87% for air dryness, and 36% for static electricity. Such com plaints were more common in new and well ventilated buildings. The sensa tion of air dryness was also more common in buildings with damp concrete slabs. In contrast, complaints about odours and stuffy air were most prevalent in old buildings with a poor outdoor air supply, and not related to building dampness. Complaints about odour were, however, more common in build ings with higher relative air humidity. Complaints of noise were related to measured noise (55 dB(A)) from the ventilation system. The high complaint rate, particularly of dry air, shows a need to improve the indoor environment in hospitals.

An important factor which reduces the quality of air supplied to a room by an air-conditioning plant is inadequate cleaning of the installation. This fault may exist in tandem with others built in during the design process (e.g. improperly placed filters with too low filtration efficiency). When, in addition to any design errors, the whole system is also badly maintained and the net work of ducts and conditioning devices are not cleaned this can result in an increase in the pollution of the air supplied to the room. For proper operation of air-conditioning it is necessary to comply with the guidelines concerning cleanliness of ventilation systems. Also, it seems reasonable to include the addition of a multi-stage filtration system, which will decrease the concentra tion of contaminants in air supplied to a room. This article describes a model of the effect of adding a four-stage filtration system to an air-conditioning system.

This article is concerned with the air quality of the closed indoor environment with respect to its temperature and carbon dioxide levels and with the assess ment of management practices that have been used to reduce temperature and carbon dioxide levels with the help of certain plants. Phanerophytic lifeforms, such as trees, shrubs, herbs and creepers surrounding dwellings can be shown to produce a cooling effect, reducing temperatures by up to 11°C. Certain succulent plants like Kalanchoe marmorata, Bryophyllum pinnata and Apicra deltoideae were observed under experimental conditions to reduce carbon dioxide levels up to 90% from closed chambers under dark conditions. Certain ornamental plants such as Verbena bipinnatifida and Ixora coccinea could remove 63-75% of carbon dioxide from closed indoor environments in the presence of light.