Unhaze / How room size is worked out
How room size is worked out, step by step.
You can check every room size on this site yourself, and check any other purifier the same way.
Step 1: Clean air per hour
Every purifier has a lab-measured CADR: how many cubic metres of clean air it gives every hour. The S5 gives 390.
Step 2: How often the room needs cleaning
Outside air keeps leaking in through doors and gaps. To keep PM2.5 down on a bad day, the room's air needs cleaning about 5 times an hour.
Step 3: The formula
This is the US appliance standard (AHAM), used by most big purifier brands. It assumes an 8 ft ceiling and about 5 cleans an hour.
room size in sq ft = CADR × 0.91
S5: 390 × 0.91 = 355 sq ft. S3: 280 × 0.91 = 255 sq ft. China's national standard (GB/T 18801) gives a similar range for the same machines.
Lab reports
Each product's test report, with the lab's name and test date, is published on its page.