What Materials are Air Filters Made Of?

Learn about what materials are used to make HVAC filters such as fiberglass, cotton gauze, stainless steel mesh and more.

What Materials are Air Filters Made Of?

An air cleaner is generally composed of a spun glass fiber material, pleated paper or cloth enclosed in a cardboard frame. Its primary purpose is to clean the air circulating in the heating and cooling system. Many people opt for a cotton-based filter when replacing their standard filter. These filters are made up of layers of cotton gauze sandwiched between an aluminum mesh, which provides a less dense material for air to penetrate than paper.

Since it is not as dense, it should theoretically be less restrictive, allowing more air to enter and increase power. However, any increase in power is likely to be small; the only noticeable change in the driving experience may be a possible change in induction noise. Fiberglass is the most common material used to make HVAC filters. As the name suggests, it is made up of thin strands of glass that are spun together to form a square or rectangular shaped HVAC filter.

Particulate air filters are devices composed of fibrous or porous materials that remove solid particles such as dust, pollen, mold and bacteria from the air. Filters containing an adsorbent or catalyst such as carbon can also remove odors and gaseous contaminants, such as volatile organic compounds or ozone. Air filters are used in applications where air quality is important, especially in building ventilation systems and engines. Air ionizers use fibers or elements with static electrical charge to attract dust particles.

Internal combustion engine air intakes and air compressors tend to use paper, foam or cotton filters. Oil bath filters have fallen out of use, apart from specialized uses. Gas turbine air intake filter technology has improved significantly in recent years due to improvements in aerodynamics and fluid dynamics of the gas turbine's air compressor part. Different standards define what qualifies as a HEPA filter.

The two most common standards require an air filter to remove (from passing air) 99.95% (European standard) or 99.97% (ASME standard) of particles that have a size greater than or equal to 0.3 μm. The cabin air filter is usually a pleated paper filter that is placed in the outside air intake of the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the engine air filter, while others are uniquely shaped to fit the available space of private vehicle outdoor air intakes. A reusable heater core filter was available as an optional accessory on Studebaker models starting in 1959, including Studebaker Lark cars (1959-196), Studebaker Gran Turismo Hawk cars (1962-196) and Studebaker Champ trucks (1960-196).

It was located directly above the heater core and was removed and installed from the engine compartment through a slot in the firewall with a long, thin rubber gasket plugging the groove when the filter was installed. The filter can be vacuumed and washed before installation. Some cabin air filters malfunction, and some cabin air filter manufacturers do not print a minimum efficiency report value (MERV) filter rating on their cabin air filters. Combustion air filters prevent abrasive particles from entering engine cylinders, leading to mechanical wear and oil contamination.

Oil-dampened polyurethane foam elements are used in some aftermarket automotive air filters. In the past, foam was widely used in air purifiers in small engines, lawn mowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-moistened foam in these applications. Foam filters are still commonly used in air compressors for pneumatic tools up to 5 Hp. Oiled cotton gauze is used in a growing number of aftermarket automotive air filters that are marketed as high-performance items.

In the past, cotton gauze had limited use in original equipment automotive air filters; however, since the introduction of Abarth SS versions, Fiat's subsidiary supplies cotton gauze air filters as OE filters. Stainless steel mesh is another example of a medium that allows more air to pass through with different mesh counts offering different filtration standards. In an extremely modified engine that lacks space for a cone-based air filter, some will choose to install a simple stainless steel mesh over the turbo to ensure that no particles enter the engine through the turbo. In the early 20th century (around 1900 to 1930), water bath air filters were used in some applications (cars, trucks, tractors and portable and stationary engines).

They worked on roughly the same principles as oil bath air purifiers; for example, Fordson's original tractor had a water bath air purifier. By 1940s oil bath designs had displaced water bath designs due to better filtration performance. Bulk solids handling involves transporting solids (mechanical conveying, pneumatic conveying) that may be in powder form; many industries handle bulk solids (mining industries, chemical industries, food industries) that require treatment of air streams escaping the process so that fine particles are not emitted for regulatory or economic reasons (loss of materials). As a result, many places within the process require an installation of an air filter; especially at reception points for pneumatic conveying lines where both amount of air and loading with fine particles is quite important.

Filters can also be placed at any exchange point within the process to prevent contaminants from entering it; this is particularly true for pharmaceutical and food industries where physical phenomena involved in capturing particles with a filter are mainly inertial and diffusional. Washable electrostatic air filters are based on an electrostatic filter medium which is usually...

Cleveland Spadafore
Cleveland Spadafore

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