Air purifier sizing Updated June 2026
What Size Air Purifier for Allergies? CADR Guide
By Yann Buf, HVAC tech 4 min read Standards-reviewed
For allergies, you need a True HEPA air purifier with CADR 200-400 depending on room size. The Coway AP-1512HH is the most recommended unit by allergists for its 4-stage filtration and auto mode.
What Makes an Air Purifier Effective for Allergies
Not all air purifiers are created equal for allergies. The key specification is CADR (Clean Air Delivery Rate) — specifically the pollen CADR and dust CADR ratings. A CADR of 200+ for pollen means the unit can effectively remove airborne pollen from a room of up to 300 sq ft.
For allergy sufferers, three features are non-negotiable: True HEPA filter (traps 99.97% of particles including pollen, dust mites, and mold spores), sufficient CADR for your room size, and 24/7 operation capability (the unit should be safe for continuous use).
The American College of Allergy, Asthma & Immunology recommends placing air purifiers in the bedroom (where you spend the most time) and running them continuously during allergy season.
Top picks for this size
Best Air Purifiers for Allergy Sufferers
- Bedroom use (150-300 sq ft): Coway AP-1512HH (CADR 246, ~$189) — allergist-recommended, auto mode adjusts to air quality
- Large room (300-500 sq ft): Winix 5500-2 (CADR 380, ~$179) — higher CADR for larger spaces, excellent value
- Whole-home approach: Place a Coway AP-1512HH in the bedroom and a Winix 5500-2 in the main living area for comprehensive coverage
Frequently asked questions
What is the difference between HEPA and True HEPA?
True HEPA is the standard that captures 99.97% of particles at 0.3 microns. "HEPA-type" or "HEPA-like" filters are not regulated and may capture significantly fewer particles. Always look for "True HEPA" certification on the product page.
Should I run my air purifier 24/7 or just during allergy season?
For best results, run it 24/7 during allergy season and while sleeping year-round. Air purifiers are designed for continuous operation and use very little electricity (30-60 watts on low). The auto mode on the Coway AP-1512HH adjusts fan speed based on air quality.
Can an air purifier help with mold allergies?
Yes. True HEPA filters capture airborne mold spores. However, an air purifier won't address the source of mold growth — you must fix moisture issues and clean visible mold. Use a dehumidifier to keep indoor RH below 50% to prevent mold growth.