How We Tested
We tested air purifiers in a 400 sq ft sealed room, measuring particle counts before and after running each unit for one hour. We used professional-grade particle counters to measure PM2.5, PM10, and ultrafine particles. Noise levels were recorded at each speed setting using a calibrated decibel meter. We calculated annual filter replacement and electricity costs to determine true cost of ownership. Smart features were evaluated for app responsiveness, data accuracy, and automation usefulness.
Coway Airmega 400
The Coway Airmega 400 is the best air purifier for most homes. Its dual-sided air intake and Max2 filters clean up to 1,560 square feet twice per hour—enough for an open-concept living area. In our testing, it reduced PM2.5 levels by 99% within 30 minutes in a 400 sq ft room. The real-time air quality indicator provides feedback without requiring an app, though smart connectivity is available. At its lowest setting, it produces just 22 dB of noise—quieter than a whisper. Annual filter costs run about $80, reasonable for this coverage level.
- Excellent coverage for large spaces up to 1,560 sq ft
- Very quiet operation at 22-52 dB range
- Real-time air quality display built in
- Large footprint takes up floor space
- Higher upfront cost than budget models
Levoit Core 400S
The Levoit Core 400S delivers impressive performance at an accessible price. It covers up to 403 square feet with a true HEPA H13 filter that captures 99.97% of particles down to 0.3 microns. The VeSync app provides real-time air quality data, scheduling, and voice control through Alexa or Google Assistant. In our testing, it matched pricier competitors in particle removal, though it takes slightly longer to clear a room due to lower airflow. At $219 with filters costing about $40 annually, it's the best value for bedrooms and small living spaces.
- Exceptional value with smart features at $219
- Low filter replacement costs around $40/year
- Compact design fits in smaller spaces
- Limited coverage for larger rooms
- Gets louder on higher speeds
CADR (Clean Air Delivery Rate) measures how much filtered air an purifier delivers per minute in cubic feet. Higher CADR means faster air cleaning. For bedrooms, look for 100-200 CFM. For living rooms, target 200-350 CFM. For large open spaces, you'll want 350+ CFM.
Frequently Asked Questions
Yes, HEPA air purifiers effectively reduce airborne allergens like pollen, dust mites, pet dander, and mold spores. True HEPA filters capture 99.97% of particles 0.3 microns and larger. For allergy relief, run the purifier continuously in rooms where you spend the most time, especially bedrooms.
For best results, yes. Pollutants continuously enter your home through doors, windows, and HVAC systems. Running on a low setting 24/7 maintains air quality while using minimal energy—most efficient models cost $3-5 per month in electricity. Turn to a higher setting during cooking, cleaning, or high-pollen days.