Air Purifiers for Allergies: What to Look For

Updated 2026-10-03

Pollen, dust and pet dander are airborne particles, and removing particles from the air is what a HEPA-type purifier does. This guide covers which numbers to compare and how to set one up. It is general information, not medical advice. If allergies affect your health, talk to your doctor about what will help.

The specs that matter

CADR (clean air delivery rate). This is the amount of filtered air the purifier delivers, in cubic feet per minute, measured separately for smoke, dust and pollen. A higher CADR cleans a room faster. Pollen grains are large, so the pollen figure is usually the highest of the three. The dust and smoke figures tell you how the purifier handles finer particles. Every model on our comparison chart lists all three.

Room size. A common rule, used by AHAM, is that smoke CADR should be at least two-thirds of the room's floor area in square feet, assuming an 8-foot ceiling. A 150 sq ft bedroom needs a smoke CADR of about 100. A 300 sq ft living room needs about 200. Going above the minimum lets you run the purifier on a lower, quieter speed. The room matcher does this math for your room.

Noise on low. A purifier only helps while it's running, and most people turn off a loud one at night. Check the lowest-speed noise level if it's going in a bedroom. See the quietest purifiers.

Filter cost. A clogged filter moves less air. Budget for replacements on the brand's schedule. Our running costs guide shows what each model costs per year.

What you can skip

• Ionizers and UV lamps. Particle removal comes from the fan and the filter. Extra features don't raise CADR.
• Thick carbon filters. Carbon is for odors and gases, not for particles. See HEPA vs carbon filters.
• Coverage claims on the box. Brands calculate "covers up to X sq ft" in different ways. Compare CADR instead.

Setting it up

• Put it where you spend the most time. For most people that's the bedroom. One purifier cleans one room, and it works best with the door closed.
• Keep windows shut in pollen season. An open window brings in pollen faster than a purifier can remove it.
• Leave it running. Particles keep entering from outdoors, clothes, pets and carpets. A low continuous speed works better than short bursts on high. More in should you run an air purifier all the time?.
• Give it space. Keep the intake and outlet clear of walls and furniture. See where to put an air purifier.

What a purifier can't do

A purifier only filters particles that are in the air. Pollen and dust that have settled on floors, bedding and furniture stay there until you vacuum or wash them. Dust mites live in fabric, not in the air. A purifier works alongside cleaning, not in place of it. For more on settled dust, see do air purifiers help with dust?. For homes with animals, see air purifiers for pet owners.

Picking one

Measure the room, find the minimum smoke CADR, then choose the quietest model above that number that fits your budget. The room matcher gives you a shortlist, and the comparison chart shows CADR, noise and filter costs side by side.