Air Purifiers An air purifier is a device which removes contaminants including dust, pollen, pet dander, mould spores, dust mite feces (which can act as allergens) and smoke particles from the air.     Air purifiers are particularly beneficial to allergy sufferers (especially those with hay fever), asthmatics, and at reducing second-hand tobacco smoke.     Air purifiers are used primarily for the following purposes:- Removing Odours from Pets, Cooking, Tobacco, Etc. Removing Mould, Mildew and Pollen Removing Chemical Gases and Paint Fumes Removing Bacteria, Viruses and Fungi Removing Dust and Smoke Particles Creating clean air Ionising the air you breath They also reduce the need for frequent household cleaning and are very energy efficient. There are different processes with varying degrees of effectiveness for purifying air. Different processes can remove different contaminants, so there can be an advantage in using more than one process in an air purifier.    The most common air purifying processes are:-    - Filter-based (normally HEPA) purification: these trap airborne particles by size exclusion: air is forced through a filter and particles are physically captured by the filter. HEPA filter specification requires remove at least 99.97% of 0.3-micrometers. They are effective down to 0.01 micrometers in many cases, but become less effective for particles smaller than 0.01 micrometer. HEPA purifiers which filter all the air going into a clean room must be arranged so that no air bypasses the HEPA filter. In dusty environments, a HEPA filter may be fitted in conjunction with an easily cleaned conventional filter (pre-filter) which removes coarser impurities so that the HEPA filter does not need to be changed or cleaned frequently.   - Activated carbon filtration: activated carbon is a highly porous material that can absorb volatile chemicals on a molecular basis, but does not remove larger particles. Activated carbon is a process of changing contaminants from a gaseous phase to a solid phase, when aggravated or disturbed contaminants can be regenerated in indoor air sources. Activated carbon can be used at room temperature and has a long history of commercial use. It is normally used in conjunction with other filter technology, especially with HEPA.    - Ionizer purifiers: these use charged electrical surfaces or needles to generate electrically charged ions. Ions attach to airborne particles which are then electrostatically attracted to a charged collector plate. This mechanism produces trace amounts of ozone and other oxidants as by-products. Most ionizers produce less than 0.05 ppm of ozone, an industrial safety standard.   There are two major subdivisions: the fan-less ionizer and fan-based ionizer. Fan-less ionizers are noiseless and use little power, but are less efficient at air purification. Fan-based ionizers clean and distribute air much faster. Permanently mounted home and industrial ionizer purifiers are called electrostatic precipitators.    Factors to consider when purchasing an Air Purifier   Frequency of filter replacement and electrical consumption are the only operation costs for any purifier.   There are many different types of filters; some can be cleaned by water, by hand or by vacuum cleaner, while others need to be replaced every few months or years. Some air purifiers are certified as energy star and are energy efficient.   Other factors to consider when purchasing an air purifier are: the area coverage; the Air Changes Per Hour, which indicates how frequently the air purifier can exchange all the air in a given room; the Clean Air Delivery Rate, which determines how well air has been purified; energy usage; and the cost of the replacement filters.     Post by Intelligent Climate. Read more about our Author