… Air quality is monitored by the EPA (Environmental Protection Agency) and is determined by the amount of air pollution that exists on any given day. In addition to quantifying the amount of particles in the air such as smoke and soot, the EPA also evaluates the levels of gases such as ozone, carbon dioxide, and sulfur dioxide. Together these pollutants determine the air quality index, a piece of information that can be used to determine how healthy the air is to breathe that day. Groups that are especially sensitive to air pollution (such as those with respiratory diseases, the elderly, and very small children) can use the air quality index to help plan how much time they should spend out of doors that day.

However, concerns about air quality are not strictly limited to outdoors. For example, those who work indoors (especially in industry) and those who suffer from allergies often make use of air purifiers to create a clean and comfortable working environment. The air quality in a room can be improved significantly by a simple air filter, which removes particles from the air based on their size or by a more complex air purifier. Air purifiers often function based on a chemical or physical property of the pollutant and are more efficient at removing toxins from the air.