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Indoor Air Quality in Office Buildings: A Technical Guide
2. Background
2.1 Sick Building Syndrome and Related Complaints
IAQ has become a significant environmental issue. The number of related complaints has increased in recent years with increased building tightness, the growing use of synthetic materials, and energy conservation measures that reduce the amount of outside air supply. Modern office equipment (e.g., photocopiers, laser printers, computers), cleaning products, and outdoor air pollution can also increase the level of indoor air contamination. The reactions to these contaminants have led to the phenomenon of sick building syndrome (SBS).
The causes of occupant complaints are multi-factorial and often elusive. It can involve chemical, microbiological, physical and psychological mechanisms. However from a rational perspective, contaminant source control is the most effective general means to improve IAQ.
Analysis of air samples may fail to reveal significant concentrations of any one contaminant, so the problem is often attributed to the combined effects of many pollutants at low concentrations, complicated by other environmental factors. For example, several factors influence thermal comfort, such as overheating, underheating, humidity extremes, drafts, and lack of air circulation. Likewise, odours are often associated with a perception of poor air quality, whether or not they cause symptoms. Environmental stressors such as noise, vibration, overcrowding, and poor workplace design and lighting can produce symptoms that may be confused with the effects of poor air quality. Further, physical discomfort or psychosocial problems (such as job stress) can reduce tolerance for substandard air.
2.2 Factors Affecting Indoor Air Quality
The indoor environment results from the interaction of the site, the climate, the building system, the potential contaminant sources (e.g., furnishings, moisture sources, work processes and activities, and outdoor pollutants), and the building occupants. Some of these factors and sources are listed in Table 1.
The heating, ventilating, and air conditioning (HVAC) system is designed to provide thermal comfort (temperature and humidity control), distribute outdoor air to occupants, remove odours and contaminants through the use of exhaust fans or dilute them to acceptable levels, and control pressure relationships between rooms. Bathrooms, kitchens, and smoking lounges should be maintained at negative pressure so that pollutants generated there do not migrate elsewhere. Computer rooms should be maintained at positive pressure to keep out dust.
2.3 Ventilation Guidelines
The generally accepted guidelines for ventilation and IAQ are ASHRAE Standard 62-1989, Ventilation for Acceptable Indoor Air Quality, and ASHRAE Standard 55-1992, Thermal Environmental Conditions for Human Occupancy.
