How a building's indoor air quality (IAQ) impacts occupant comfort and health is complex and not completely understood. There are many factors that can affect IAQ, such as human activity within the building, the building's construction materials, and the types of heating, ventilation, and air conditioning (HVAC) systems present. Common human activities that can affect IAQ include the use of copiers, pesticides, and cleaning products. Building materials and the HVAC system can vary with the age of the structure. Newer buildings may have significant toxic offgassing from furnishings, paint, and particleboard, but also may have better air filtering and exchange systems. Older buildings may have cellulose wallboard (which is susceptible to mold), asbestos ceiling tiles, lead-paint dust, and/or leaky ventilation systems. The outdoor environment can also significantly affect IAQ. Dry, windy climates increase dust. Warm, humid climates have more insects, pollen, and mold.
Poor IAQ can certainly affect occupant' health and comfort levels—sneezing and runny noses are uncomfortable and a sign of adverse health effects. Room temperature and humidity can both affect immediate physical comfort and influence IAQ. There is a relationship between temperature, humidity, IAQ, and comfort. Comfort relates primarily to the temperature, the amount of clothing being worn, relative humidity, and air movement. There is no one temperature where everyone feels comfortable, but the typical range of acceptable indoor air temperatures is from 68° to 72°F. Relative humidity is also important in comfort, with an acceptable range of 30–65%. At a relative humidity below 30%, people can suffer dry mucous membranes, which can lead to nosebleeds and infections. Low relative humidity is a typical problem found in winter months when the outside air is very dry. High relative humidity above 65% can lead to mold, mildew, and other biological growth. Mold growth is linked to allergic reactions, asthma attacks, and hypersensitivity pneumonitis (inflamed airways). Mold growth can be controlled by quickly eliminating any sources of water caused by leaks and maintaining relative humidity levels below 65%.
