Here are some useful terms to understand when purchasing an air purifier:

AHAMAssociation of Home Appliance Manufacturers. They are an organization that independently verifies the manufacturer's claims on recommended room size and CADR (clear air delivery rate). They are also recognized by the EPA as a Certification Body and are approved to verify Energy Star requirements. 

CADR: Clear air delivery rate. This indicates the volume of air filtered by the purifier. AHAM tests purifiers on three categories — dust, tobacco smoke, and pollen — and assigns a CADR number to each. The higher the CADR numbers, the faster the purifier performs.

Energy Star: Energy Star approved air purifiers are 40% more energy efficient than standard models. To meet the performance requirement, air purifiers must have at least 2.0 CADR per Watt. 

Ionizer: Some purifiers use ionizers to trap and absorb particulates. What happens is these ionizers use an electromagnetic charge to either add or remove electrons from the particles in its vicinity. This gives the particles a negative charge or a positive charge respectively and ionizes them. 

Once the particles is ionized, the purifier pulls them and the ions settle onto the filter due to its charge. 

The problem with ionizers is ozone is a natural byproduct of this process. Ozone is a known irritant on lung and respiratory systems. If you suffer from allergies and respiratory problems such as asthma, stay away. Ozone will only aggravate your symptoms further. 

HEPA: High-efficiency particulate absorber. HEPA filters consist of randomly arranged fibers which are made mostly of fiberglass. As the fan pulls air into the filter, particulates 0.3 microns or larger are absorbed by the HEPA filter.

To qualify as a HEPA filter by government standards, the filter must be able to absorb 99.97% of these particulates. You can find HEPA filters used in medical facilities, automobiles, aircraft, and homes. 

VOC: Volatile organic compound. VOCs are gases emitted by certain solids or liquids such as the furnace, cleaning products, paints and other household products. These gases carry health effects such as:

  • Eye, nose and throat irritation
  • Headaches, loss of coordination and nausea
  • Damage to liver, kidney and central nervous system
  • Some organics can cause cancer in animals, some are suspected or known to cause cancer in humans.


The EPA has found that indoor air has 2 to 5 times more VOCs than the air outdoors. This is consistent across both rural homes and urban dwellings. 

UV-C: Other purifiers use ultraviolet light to destroy particulates. What happens is the fan pulls in air, and once the air is inside the purifier, they are exposed to ultraviolet light which destroys the germs and bacteria.