Air quality is affected by the contaminants that are emitted into the atmosphere. These contaminants include gases, aerosols, vapors, and particles. Exposure to indoor air pollution has increased for a number of reasons, including buildings that are sealed more securely and the reduction of ventilation systems. The use of synthetic materials, chemical products, pesticides and cleaners also decreases air quality. Volatile organic compounds, pesticides, tobacco smoke, and chemical or biological pollutants all have a negative impact on air quality.

Poor air quality causes a number of problems, from something as simple as a foul odour to something as complex as sick building syndrome. In order to improve air quality, the amount of contaminants must be decreased or eliminated. This is achieved by destroying the pollutant through combustion, transforming the pollutant to a form that is less toxic, or collecting the pollutant with equipment that prevents its escape into the environment. Installing and maintaining HVAC systems that meet ventilation standards can achieve higher air quality management. When properly designed, installed, maintained and operated, an HVAC system is essential for air quality. If the HVAC system is not properly taken care of, it can actually generate and contribute to poor air quality by dispersing air pollutants. Source control, ventilation, and air cleaning are all part of the proper upkeep of an HVAC system in order to ensure air quality..