Air is colorless, odorless, tasteless, gaseous mixture, mainly nitrogen and oxygen with lesser amounts of other gases. This mixture with varying amounts of moisture and particulate matter,forms the atmosphere. Air pollution occurs when the air contains gases, dust, fumes or odor in harmful amounts. It primarily consists of following subsectors: 1 Air Purifier A device used to remove impurities from the air  2 Air Quality Measurement A measurement of the pollutants in the air; a description of healthiness and safety of the atmosphere 3 Smoke detectors A device that automatically detects the presence of smoke and raises alarm. Also called smoke alarm