Exposures to indoor air pollutants and their ensuing health effects are generally classified as acute or chronic. Acute exposure to a chemical is usually measured in minutes or, in some cases, seconds. Acute health effects are those manifested almost immediately (e.g., irritation of mucous membranes, cough). Chronic exposure to a chemical refers to a repeated exposure over a long duration, usually measured in days, months, or years. Chronic health effects are those that develop and persist over time (e.g., cancers, liver and kidney effects) and, therefore, their appearance may not coincide with exposure to the causative agent(s).

The most common adverse health responses associated with poor IAQ are often subtle and not always immediately linked to indoor air contamination. The symptoms reported are often non-specific rather than clearly defined illnesses. Typical IAQ-attributed symptoms include headache, fatigue, cough, sneezing, dizziness, nausea, and irritation of the eyes, nose, throat, and skin.

A wide variety of pollutants may be associated with laboratories. Depending on the quantities released and the duration of exposure, these contaminants can produce a range of health effects and symptoms.

There is no clear division between physical discomfort and the onset of health symptoms, or between the perception of odors and irritant effects. However, as odors become stronger, more and more people will experience olfactory irritation which will eventually be manifested in IAQ symptoms. Individuals’ responses to odors vary widely. Some people are extremely sensitive to certain odors and will find almost any level objectionable and discomforting.

Researchers have found that it is virtually impossible to identify temperature ranges that all segments of the population find comfortable. The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) developed a "comfort chart" that describes ranges of temperature and humidity that should be acceptable to approximately 80% of the population. Spaces below 68 degrees Fahrenheit and 30% relative humidity in the winter, and above 78 degrees Fahrenheit and approximately 60% relative humidity in the summer are expected to produce discomfort in larger portions of the school population. Low relative humidity environments dry out the skin and mucous membranes, and high humidity limits the body’s ability to shed excess heat. High humidity is also conducive to mold growth. Temperatures in laboratories may increase due to the operation of heat sources (ovens, burners, etc.), and humidity may rise because of a nearby greenhouse.