Air filters are devices used to minimize or remove unwanted particulates from the air. This may be air flowing within a ventilation system, or it might be air moving through an open indoor space. Industrial air filtration systems improve indoor air quality and extend the working life of machinery, engines and appliances.
Types of spaces and products that air filters clean include in-home and commercial heating systems, ventilation systems, air conditioning systems, humidifiers, engine components, cars, and direct air machines. Particles that individual air filters remove fluctuate, but some include mold spores, animal dander, and dust and pollen.
Filtration systems are used residentially, commercially, and industrially to physically remove contaminants from air, liquid, gas, or powdered substances. The process of separating a fluid substance into two or more distinct factions is often accomplished through the use of a screen, film, or membrane. The fluid may be vacuum or pressure driven, or gravity fed through the filtration device to remove particles or contamination. Other methods of filtration include centrifugation, and chemical, biological, or electrical processing.
Air and water are the most common fluids to go through the filtration process. Other process fluids include food and beverage products, petrochemicals, paints, plating solutions, photographic solutions, pharmaceutical products, chemicals, lubricants, gases, fuels, coolant, and cosmetics.
There are several different manners in which filtration systems separate materials in a mixed process stream. Membrane filtration involves the use of media that trap contaminants. Foams and other materials employ similar techniques; additional filtration options include the use of gravity, centrifugal force, chemical solvents, biological agents and even electrically charged apparatus. Gravity and centrifugal force filters use hydrostatic or rotational pressures, which remove heavier particles from the flow line. Chemical filters function by either dissolving specific contaminants or attracting them and, through the use of gravity, pulling them from the system. Not as common, but thoroughly effective, biological filters use digestive microbes to remove unwanted organic compounds. There are two main types of filtration systems that depend upon the use of electrical charges to purify air and fluid supplies. Electrodialysis (ED) uses membranes that allow the passage of either positively or negatively charged ions while excluding the passage of the opposite. Because ED membranes are easily clogged, many filters are equipped with electrodialysis reversal (EDR) systems instead. It works in the same way as ED systems, but it periodically reverses the electrical current in order to exchange the fresh product flow. Reverse osmosis (RO), electrodeionization (EDI) and ultrafication (UF) processes are less common but equally efficient options. Each type has benefits and advantages particular to specific filtration applications.
Liquid filters clean or purify liquids that run through them. All liquid filters operate by passing a liquid through a semi-permeable or porous substance, which allows the liquid molecules to pass through, but blocks large particulates and chemicals.
Note: The word "filter" actually refers to the housing or holding mechanism of a filtration system. "Filter media" refers to the porous barrier, chemical or mat clarifies the liquid.