Air Purifier Manuals & Owner Guides

CADR and room size explained

Clean air delivery rate (CADR) is the volume of particle-free air a purifier delivers, in cubic feet per minute, measured separately for smoke (the finest particles), dust and pollen. PM2.5 CADR, now used for ENERGY STAR certification, is calculated from the smoke and dust results to represent fine particles.

The recommended room size follows the industry rule of thumb that smoke CADR should be at least two-thirds of the room area — roughly 1.55 sq. ft. per CFM, or about 4.8 air changes per hour with an 8 ft ceiling. For allergies, asthma or wildfire smoke, choose a purifier rated for a larger room than the one you are treating.

Filter types

HEPA

Meets the HEPA standard of capturing at least 99.97% of 0.3-micron particles.

HEPA-type

A manufacturer description for high-efficiency pleated media that is not certified to the HEPA standard. Compare CADR instead of the label.

Activated carbon

Adsorbs odors and some gases; it does not capture particles and must be replaced when saturated.

Ionizers and electrostatic plates

Charge particles so they are easier to collect. They can produce small amounts of ozone; check the ozone figure on each model page.

Energy use

ENERGY STAR rates purifiers by integrated energy factor — PM2.5 CADR per watt, including standby power. Because purifiers run many hours a day, an efficient model can save a meaningful amount over its life; annual kWh figures assume about 16 hours of operation per day.

Air Purifier FAQ