Air purifier glossary: Commonly used terms and definitions

CADR: Clean Air Delivery Rate (CADR) signifies the amount of clean air delivered by an air purifier.  Three numbers are usually listed for each air purifier (one for tobacco smoke, one for pollen, and one for dust).  The higher the tobacco smoke, pollen and dust numbers, the faster the unit filters the air.  The CADR determines how well an air purifier reduces these pollutants.

Carbon/Zeolite: Carbon and zeolite are materials used in some air purifiers that remove gases and odors. Both have properties that allow them to absorb gaseous materials and pollutants.  Zeolite is a cheaper version and is not nearly as effective as carbon.

CFM: Cubic feet per minute. The amount of air, in cubic feet, that flows through a given space in one minute. 1 CFM equals approximately 2 liters per second (l/s).

HEPA: Stands for High Efficiency Particulate Air. HEPA filters can capture 99.97% of particles as small as 0.3 microns.  Can also capture 95-99% of particles below 0.3 microns.  HEPA filters were originally designed to capture and remove microscopic particles such as radioactive dust in atomic plants.  HEPA filters are a mainstay in areas that require clean air such as hospitals, clean rooms, and high-tech manufacturing plants.

Ionic (Electrostatic Precipitator): Basically, air is drawn through an electrical field.  As the particles in the air pass through the electrical field, an electronic charge is given to them. The charged particles are then attracted to a series of flat plates with an opposite electrical charge. Effectively removes many particles from the air, such as allergens, fine dust particles, some bacteria and viruses, chemical fumes and other ultra-fine particles.  This process usually causes a small amount of ozone to be created.

Ozone: A unstable derivative of oxygen, O3, that is formed naturally in the ozone layer from atmospheric oxygen by electric discharge or exposure to ultraviolet radiation.  It is a highly reactive oxidizing agent used to deodorize air, purify water, and treat industrial wastes.

Prefilter:  A filter used in many air purifiers that is designed to capture particles 1 micron in size and larger.  Some air purifiers used activated carbon as their prefilter to remove odors and gases.  A prefilter will extend the life of a HEPA filter.

Ultraviolet light: The part of the light spectrum that is below 400 nm and invisible to the human eye.  Ultraviolet light is used in some air purifiers to destroy microorganisms such as bacteria, mold and viruses.