The air purifier is an electronic device that clears the air of any pollutants, contaminants, dust, and viruses. The air purifiers, by capacity, are of two types: one is stand-alone air purifiers which are used for single, small-sized rooms, and the other type is large-unit air purifiers which can be attached to the HVAC or AHU to purify the air of an entire building or such.
By the purifying technologies, air purifiers can be categorized into two main types: active and passive air purifiers. The first one uses "-ve" -ly charged ions to make the pollutants stick to the surface, whereas the other uses air filters for purification. The filtration techniques are different depending on the place and the type of air needed to be cleaned.