Air Purifier Glossary: A

With so many acronyms and terms, the air purifier space can get confusing. Here are some frequently encountered stumbling blocks which begin with the letter "A," with my attempts at clarification.

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ABS

Acrynom for Acrylonitrile Butadiene Styrene, the rigid thermoplastic used to make injection molded products including air cleaners. ABS is one of the most inert plastics and outgasses very little at normal air cleaner operating temperatures.

ACH

Acrynom for Air Changes Per Hour, see Air Change Per Hour Simplified

Activated Carbon

Also called activated charcoal, activated carbon is the most common odor/chemical adsorption medium in residential air purifiers. Activated carbon is made by heating bituminous coal, wood or coconut shell to around 800-900 degrees Celsius, forming a carbonized char. This is oxidized to create a highly porous adsorbent material. A pound of activated carbon has an internal surface area equal to about 125 acres.

Active Air Treatment

As opposed to passive filtration, which requires pollutants to go through the air purifier, active air cleaning reaches out into the space near the air purifier, attacking ultrafine and molecular pollutants. Plasma-ion, negative ion, and ozone are included.

Absorption

Absorption is a process in which a pollutant, either particle or gas, is taken up by a filter medium, through minute pores or spaces between its molecules. A paper towel absorbs water.Compare Adsorption

Adsorption

Adsorption is how gas molecules stick to the internal surfaces of a medium (the adsorbent) by molecular attraction. For example, odor molecules being adsorbed by activated carbon. Different molecular structures are held more of less tightly, depending on polarity.

Compare Adsorption

Adsorbent

See Adsorbtion above.

Typical air cleaner absorbents are activated carbon and zeolite.

Aerodynamic Diameter

Aerodynamic diameter refers to the fact that airborne particles have irregular shapes which are difficult to measure. Aerodynamic diameter assumes particles are spheres. AD is used to evaluate the depth to which inhaled particulate will penetrate the respiratory tract.

AHAM

Acrynom for Association of Home Appliance Manufacturers. CADR: AHAM Air Cleaner Capacity Certification

Airborne

Airborne is used to denote particles light enough to remain suspended, floating in the air. Air currents will increase the concentration and decrease the settling rate.

Air Exchange

The rate at which outside air replaces indoor air in a house or room by seepage. A measure of the tightness of construction - Not the same as air changes per hour, but widely misquoted as the same.

Airflow

A metric, measured in cubic feet per minute (CFM) for the amount of air that moving through an air purifier.

Airflow is not exactly the same as CADR, which uses actual efficiency measurements to modify a rating.

Airflow is important, but is only one factor in air purifier performance.

Air Sterilizer

A germicidal technology, using heat and/or ultraviolet radiation to destroy airborne mold spores, bacteria, fungi, and viruses. Generally these are filter-less and very slow acting.

The term "Air Sanitizer" is becoming popular due to the low efficiency of these machines, inconsistent with the 100% removal implied by "sterile."

Animal Dander

Dander is particles shed from various animals, similar to dandruff. It may consist of dried skin flakes, hair shards, or feather fragments. While airborne dander is frequently associated with allergy, it is often the animal's saliva proteins that are the main source.

These proteins are transferred mainly by non-airborne interactions with the pet or its habitations.

ASHRAE

Acronym for American Society of Heating, Refrigeration and Air Conditioning Engineers, Inc.

ASHRAE standards apply to testing and comparing the efficiency of HVAC (furnace) filters, rather than room air cleaners.

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