Air purifiers

An air purifier or air cleaner is a device which removes contaminants from the air in a room. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating second-hand tobacco smoke. The commercially graded air purifiers are manufactured as either small stand-alone units or larger units that can be affixed to an air handler unit (AHU) or to an HVAC unit found in the medical, industrial, and commercial industries. Air purifiers may also be used in industry to remove impurities such as CO₂ from air before processing. Pressure swing adsorbers or other adsorption techniques are typically used for this.

In 1830, a patent was awarded to Charles Anthony Deane, which was for a device comprised a copper helmet with an attached flexible collar and garment. A long leather hose attached to the rear of the helmet was to be used to supply air, the original concept being that it would be pumped using a double bellows. A short pipe allowed breathed air to escape. The garment was to be constructed from leather or airtight cloth, secured by straps.

In the 1860s, John Stenhouse filed two patents applying the absorbent properties of wood charcoal to air purification (patents 19 July 1860 and 21 May 1867), thereby creating the first practical respirator.

A few years later, John Tyndall invented an improvement to the fireman's respirator, a hood that filtered smoke and noxious gas from air (1871, 1874).

In the 1950s, HEPA filters were commercialized as highly efficient air filters, after being put to use in the 1940s in the United States' Manhattan Project to control airborne radioactive contaminants.

Dust, pollen, pet dander, mold[thrive in damp and humid areas] spores, and dust mite feces can act as allergens, triggering allergies in sensitive people. Smoke particles and volatile organic compounds (VOCs) can pose a risk to health. Exposure to various components such as VOCs increases the likelihood of experiencing symptoms of sick building syndrome. Air purifiers are becoming increasingly capable of capturing a greater number of bacterial, virus, and DNA damaging particulates.

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