Indoor Air Quality

The primary objective of a building is to provide an environment that sustains the activities carried out within. City dwellers spent most of their time inside buildings, in homes, places of leisure and workplaces. For a quality lifestyle, safe, healthy and comfortable indoor environments are needed. There is a relationship between productivity, space comfort, indoor air quality and occupant satisfaction, which optimises energy use, owner needs and employee evaluation of workspace conditions.

When occupants are exposed to an environment that results in discomfort or illness, unnecessary costs may be incurred through absenteeism or loss of productivity. Investments in improving the quality of design, construction and maintenance of buildings which result in only decreased absenteeism or increased productivity, are highly cost-effective. Comfort conditions can be quantified in terms of air temperature and movement, relative humidity, lighting quality, noise, etc.

Setting up sophisticated air quality monitoring systems in the Department's Indoor Air Quality Laboratory

Indoor air quality may be defined in terms of 'freshness', usually defined by carbon dioxide level, and by 'purity', i.e., acceptable levels of annoying or harmful pollutants. Still or stale air may be discomforting, but the health impacts of polluted air can be more serious, from irritation, temporary debilitation to severe illness.

Pollution indoors can arise from outdoors, through outside air intakes and from uncontrolled infiltration. Congested streets, industrial effluent, construction sites, etc., contribute to the pollution of local ambient air. High traffic densities and vehicular access into buildings introduce an array of pollutants the potency of which is of increasing concern. Air duct linings, dirty air handling equipment, etc., contaminate during the conditioning and transport of air. Internal sources of pollutants are people, smoking, equipment, furniture, finishes, etc.

Interior lighting has a significant impact on the quality of the indoor environment affecting occupant comfort and productivity. However, as discussed in the section on Electrical Services, the design of lighting systems needs to embrace energy efficiency and power quality issues also.

Noise and vibration have substantial impact on humans and their control is indispensable in the establishment up of a comfortable indoor environment. Inside a building, noise and vibration problems come mainly from the air conditioning systems, human activities, mechanical services and the break-in noise from outdoors.

Research Focus

The Department research focuses on evaluating the environmental conditions found inside buildings. The Department recently completed a large scale in-office stud covering the measurement of thermal comfort, indoor air quality, noise and lighting. The extensive database obtained is useful in determining the optimum design criteria for indoor environments. Several prototypes for logging indoor environmental parameters have been developed. These can monitor continuously the physical environment and subjective responses of occupants.

The work continues with measurement of ventilation system performance. A measurement methodology for evaluating ventilation performance in large office spaces has been developed based on monitoring metabolic carbon dioxide, tracer gas decay and air flow measurements. Studies on indoor air pollution targets those pollutants which are of most concern locally: radon, biological, carbon monoxide, and volatile organic compounds.

The noise and lighting surveys reveal very useful information for enhancing the design of open plan offices. Research on noise control, standard testing of sound power, sound absorption, flow noise and office noise characteristics are in progress.

Specialist Facilities

An Indoor Air Quality Laboratory was set up in 1993 with a large grant from the Research Grants Council. The test rigs in this laboratory are mostly portable, comprising various gas analysers, temperature, humidity and air flow sensors, etc., for measurements in occupied spaces, on air-side systems, etc.. Test rigs have been developed for the evaluation of thermal comfort, indoor air quality and ventilation performance.