Terms and Terminology

CADR
Clean Air Delivery Rate. The CADR indicates the volume of filtered air delivered by an air cleaner. CADR is provided for three numbers: tobacco smoke, pollen, and dust. A higher CADR rating indicates faster air filtration. AHAM advises you to choose a unit with a tobacco smoke CADR of at least 2/3 your room's area.

AHAM
The Association of Home Appliance Manufacturers is an organization which verifies testing results for home appliances like refrigerators, air conditioners, humidifiers, and air purifiers. They use outside labs to test products, and CADR is their official rating for air purifiers.

HEPA filter
High Efficiency Particulate Air filter. A HEPA filter is not made by any one company or brand; it is a standard in air filtration. HEPA filters can remove at least 99.97 of particles 0.3 microns and larger. Be aware of filters marketed as "HEPA-type" filters – these are filters which have the same general construction as a HEPA filter, but failed to meet the standard and may be much less efficient at removing particles.

HEGA filter
High Efficiency Gas Absorption filter. This kind of filter is made out of carbon cloth, which can be more efficient than activated carbon in the granular form. Some HEGA filters incorporate both HEPA and carbon cloth (for absorption of both particles and gases).

CFM
Cubic Feet per Minute. This is the amount of air that the fan on the air purifier can circulate in one minute. In other words, the CFM is a measurement of how much space an air purifier can clean (and keep clean). For a much lengthier explanation, see step #1 in "Buying an Air Purifier".

Activated Carbon
This is carbon which has been treated with oxygen to open up millions of pores, creating an enormous surface – 60 to 150 acres in just one pound! This super-porous carbon is used to trap gases, chemicals, and odors, which stick to the surface through a process called "adsorption". Impregnated activated carbon has been treated with additional chemicals (called chemisorbents) which enhance its ability to remove certain specific chemicals.

Ozone
Ozone is a molecule which has three atoms of oxygen. The normal oxygen molecule we breathe has two atoms of oxygen. In an ozone molecule, the third oxygen atom is very unstable and can re-attach to other molecules easily, altering their chemical composition. For this reason, it is used in some "air cleaners" to react with certain harmful chemicals, in a process which is intended to render them harmless. However, this can leave behind certain other harmful chemical by-products. Ozone itself is a known lung irritant, which can cause chest pain, lung inflammation, aggravation of asthma, and other health problems, as documented by the EPA. Ionizing and electronic air purifiers can also create ozone as a byproduct.

Mechanical air purifiers
This is a technical term used to describe a certain kind of air purifier. Mechanical air purifiers have fans and filters. They are HEPA or carbon type filters. In general, we highly recommend these types of air purifiers, which are safer and more effective.

Electronic air purifiers
As opposed to mechanical filtration, electronic air cleaners generally do not have filters and usually do not have fans. They use a process of ionization or electrostatic charging to either collect the particles, or cause them to fall out of the air. While we do not recommend most electronic air purifiers, there are a few units which have been tested to be effective and safe. The Friedrich air purifier is a good example of an electrostatic precipitator. Blueair air purifiers use a combination of electronic and mechanical filtration, and are also highly recommended.

VOC
Volatile Organic Compound. VOC's are chemicals which contain carbon (which makes them organic) and which evaporate easily at room temperature (which makes them volatile). These are chemicals like benzene, toluene, methylene, chloride, formaldehyde, and many others. They are commonly emitted by ubiquitous household and office products: paints, varnishes, cleaning supplies, new carpets, copiers and printers, air fresheners, and other sources. They can cause various health problems, as well as allergic reactions in those who are chemically sensitive.

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The best air purifiers, by far, are manufactured by IQAir. The IQAir HealthPro has been featured on popular television shows, and is a bestseller.