Buying guide
Air Purifier Buying Guide (2026)
How to choose an air purifier: HEPA truth, CADR and room sizing, noise, filter costs, and features worth paying for.
HEPA and the stages that matter
Look for True HEPA, not HEPA-type or HEPA-like, which are weaker standards. A good purifier pairs True HEPA with an activated carbon stage for odors and a pre-filter for large particles. Extra stages like UV-C or ionizers are optional; the HEPA and carbon do the proven work.
Sizing: CADR and room coverage
CADR (clean air delivery rate) measures how much clean air a unit delivers. A practical rule: CADR should be at least two-thirds of your room's square footage. Manufacturer room ratings are useful, but AHAM-verified figures are the most trustworthy. An undersized purifier in a big room is nearly useless.
Noise: the spec that decides use
The best purifier is the one you never turn off, so check sleep-mode decibels. Anything around 25 dB or lower disappears into bedroom background. Turbo-mode noise matters less, since you will rarely use it. If the unit will sit near a desk or bed, prioritize quiet over raw power.
The real cost: filters
Replacement filters typically cost a meaningful fraction of the unit price and need changing every 6 to 12 months. Before buying, check the filter price and lifespan, then multiply by three years. A cheap purifier with expensive filters is often the pricier choice.
Questions, answered
What is CADR?
Clean Air Delivery Rate: the volume of filtered air a purifier delivers, measured separately for dust, pollen, and smoke. Higher is better, and AHAM-verified ratings are the gold standard.
Do I need an air quality sensor?
Not essential, but useful. Sensors drive auto modes that keep noise low when air is clean and ramp up during pollution events. Without one, you manage fan speed manually.
Are ionizers safe?
Most modern purifier ionizers produce negligible ozone, well under safety limits. If it concerns you, choose a model where the feature can be switched off.
Where should I place my purifier?
In the room you use most, with at least a foot or two of clearance on the intake sides. Bedrooms are the highest-value placement for most people.