Air Filters

An air filter is a device which removes contaminants, often solid particulates such as dust, pollen, mold, and bacteria from air. more...

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Air filters are used in application where air quality is important, notably in building ventilation systems and in engines, such as internal combustion engines, gas compressors, diving air compressors, gas turbines and others.

Some buildings, as well as aircraft and other man-made environments (e.g., satellites and space shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method uses fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favor. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid-dynamics of the air-compressor part of the Gas Turbines.

Climate control air filters

There are four main types of mechanical air filter media: paper, foam, synthetics and cotton.

Air filters are found in most all forced-air heating, ventilation, and air conditioning systems. The efficacy of the air filters in such systems significantly affects the Indoor Air Quality. The [[United States Department of Energy advises that " Filtration should have a Minimum Efficiency Reporting Value (MERV) of 13 as determined by ASHRAE 5.2.2-1999." There are a variety of different types of HVAC filters available. Many are inexpensive and not very efficient. Some options are panel, pleated, electrostatic, HEPA, electronic and media. ASHRAE recommends (MERV 6 or higher) air filters to lower the amounts of pollen, mold and dust that reaches the wet evaporator coils in air conditioning systems. Wet coils contaminated with high levels of pollen and dust can allow mold colonies to grow.

Polyester and/or glass fibres are commonly used to make web formations used for air filtration. Both materials have high temperature ratings of at least 250°F / 120°C, and are widely used in commercial, industrial and residential applications. Polyester and glass fibres can be blended with cotton or other fibres to produce a wide range of performance characteristics. In some cases Polypropylene, which has a lower temperature tolerance, is used to enhance chemical resistance. Tiny synthetic fibres knows as microfibres are used in many types of HEPA (High Efficiency Particulate Air) filters.

Many in-duct filters for home forced air heating and air conditioning systems are made from plain, loosely-spun fiberglass. These filters are inexpensive, disposable, and come in various densities and sizes. Less-dense filters allow for higher airflow, but do not remove as much dust. Higher density filters remove more particles, but are more expensive and offer more resistance to the air. They also become more quickly "loaded" with contaminants and dust. They are considerably less expensive than pleated-paper filters for the same size.

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