Demystifying Clean Air Delivery Rates (CADR): How to Size True HEPA Air Purifiers
The physics of cubic-feet-per-minute air volume, ACH ratings, and avoiding undersized room filters during wildfire season.
Manufacturers often claim their air purifier covers "up to 1,000 square feet," but how long does it take? Here is how to calculate true room protection.
Key Editorial Takeaways
- Always calculate room coverage based on at least 4 ACH (air changes per hour), not 1 or 2 ACH.
- True HEPA (H13) filtration captures 99.97% of particles down to 0.3 microns without producing harmful ozone.
- Activated carbon thickness dictates whether an air purifier can neutralize VOCs and chemical paint fumes.
The most common mistake consumers make when purchasing an air purifier is relying on the manufacturer’s advertised square footage claims without checking the Air Changes Per Hour (ACH) rate and independent CADR test scores.
Clean Air Delivery Rate (CADR), established by the Association of Home Appliance Manufacturers (AHAM), measures the cubic feet of clean air a purifier delivers per minute across three specific pollutants: smoke (smallest), dust (medium), and pollen (largest).
To effectively protect against acute asthma triggers, virus aerosols, or dense wildfire smoke, your room requires at least 4 to 5 Air Changes Per Hour. An air purifier with a CADR of 250 CFM can cycle the air in a 350-square-foot living room four times every 60 minutes.
Featured Products Mentioned in this Piece
Coway Airmega 250 True HEPA Air Purifier
High-performance True HEPA and activated carbon filtration covering up to 930 sq ft with real-time PM2.5 particulate LED monitoring.
Dyson V15 Detect Cordless Vacuum Cleaner
High-suction cordless vacuum featuring laser dust illumination, acoustic piezo particle sensor, and auto-adjusting power.
David Ross
Outdoor & Fitness Researcher
David investigates outdoor apparel, trail gear, and fitness trackers. He looks past marketing buzzwords to evaluate durability, material sustainability, and realistic user value.