How to Compare Air Purifiers Using CADR and Room Size
Avoid vague air-cleaner marketing claims by checking room size, CADR, filter replacement costs, and ozone concerns.
Before deciding, identify the exact problem you want to solve and the information you can verify independently. The steps below focus on practical checks, common failure points, and what to do next.
Start with the problem and room
Decide whether the main concern is airborne particles such as smoke, dust, or pollen, or gases and odours. Portable particle filters are not a universal solution to every indoor-air problem, and ventilation or removing the source can matter more.
Measure the room's length and width and note ceiling height. Open-plan rooms and high ceilings affect the amount of air a cleaner must process.
Compare performance rather than slogans
Look for clean air delivery rate (CADR), especially smoke CADR when comparing particle filtration. A higher CADR generally means faster particle removal in a given room; check the stated measurement and room-size assumptions.
EPA provides guidance for comparing portable air cleaners. Terms like medical grade or advanced purification are less useful than independently specified performance and a clear explanation of what is removed.
Estimate the real ongoing cost
Find the replacement filter price and recommended change interval, then add electricity use and noise considerations. A purifier that is loud enough to be turned off may provide little practical benefit.
Check the replacement filter's availability in your region. Compare a year of ownership, not just the headline purchase discount.
Avoid false reassurance
Some air-cleaning technologies intentionally produce ozone, which can irritate the respiratory system. Prefer designs with clear evidence and appropriate safety information; do not substitute a purifier for controlling mould, smoke sources, or needed medical care.
Place the unit where air can circulate freely and maintain it according to the official manual.