Human responses to pollutants, climatic factors and other stressors such as noise and light are generally categorized according to the type and degree of responses and the time frame in which they occur. Building managers should be generally familiar with these categories, leaving detailed knowledge to health and safety professionals.

Acute Effects: Acute effects are those that occur immediately (e.g., within 24 hours) after exposure. Chemicals released from building materials may cause headaches, or mold spores may result in itchy eyes and runny noses in sensitive individuals shortly after exposure. Generally, these effects are not long lasting and disappear shortly after exposure ends. However, exposure to some biocontaminants (fungi, bacteria and viruses) resulting from moisture problems, poor maintenance or inadequate ventilation have been known to cause serious, sometimes life threatening respiratory diseases which themselves can lead to chronic respiratory conditions.

Chronic Effects: Chronic effects are long-lasting responses to long term or frequently repeated exposures. Long term exposures to even low concentrations of some chemicals may induce chronic effects. Cancer is the most commonly associated long term health consequence of exposure to indoor air contaminants. For example, long term exposure to the following increases cancer risk:

• environmental tobacco smoke
• radon
• asbestos
• benzene

Discomfort: Discomfort is typically associated with climatic conditions but building contaminants may also be implicated. People complain of being too hot or too cold or experience eye, nose or throat irritation because of low humidity. However, reported symptoms can be difficult to interpret. Complaints that the air is "too dry" may result from irritation from particles on the mucous membranes rather than low humidity, or "stuffy air" may mean that the temperature is too warm or there is lack of air movement, or "stale air" may mean that there is a mild but difficult to identify odor. These conditions may be unpleasant and cause discomfort among occupants, but there is usually no serious health implication involved. Absenteeism, work performance and employee morale, however, can be seriously affected when building managers fail to resolve these complaints.

Performance Effects: Significant measurable changes in people's ability to concentrate or perform mental or physical tasks have been shown to result from modest changes in temperature and relative humidity. In addition, recent studies suggest that the similar effects are associated with indoor pollution due to lack of ventilation or the presence of pollution sources. Estimates of performance losses from poor indoor air quality for all buildings suggest a 2-4% loss on average. Future research should further document and quantify these effects.