How to Choose an Air Purifier in 2026

Air purifiers on a shelf look much the same: a box, a fan, a filter. The published specifications are where they diverge, and five of them account for almost all of the difference — clean air delivery rate, the coverage figure and the air-change rate behind it, the filtration stages in the airflow, the noise range, and filter life. This guide explains what each changes, then lays three units out side by side.

CADR is the only spec that measures output

Clean air delivery rate is given in cubic feet per minute and describes how much filtered air the unit delivers, tested against smoke, dust and pollen. It combines fan output and filter resistance rather than describing either alone, which makes it the category’s nearest thing to a single performance number.

Two things to watch. Manufacturers do not all publish it the same way — Coway breaks the figure out per pollutant, Levoit publishes a single combined CFM number for the Core 300S-P — so the three units are not reported on quite the same basis. And CADR stops mattering once it comfortably exceeds the room: a unit rated well beyond your square footage does not clean the air past clean, it just spends more of its life on a lower, quieter fan speed.

A coverage figure means nothing without its air-change rate

Every coverage number is really a pair: square footage and how many times an hour the unit turns that volume over. The table uses the one-air-change-per-hour basis because all three manufacturers publish it — and because it is the most generous basis available.

At 4.8 air changes per hour, the rate usually quoted for pollen or smoke, Levoit publishes the Core 300S-P at 219 sq ft rather than 1,051, and Coway the Airmega 200M at 361 sq ft rather than 1,748. The ProX publishes no 4.8-ACH figure at all; its pair stops at two changes an hour in 2,126 sq ft.

Compare coverage figures only at the same rate, and decide which rate you need first: one or two changes an hour is a general dust setting, four to five is what allergy and smoke use asks for.

Filtration stages describe what gets captured, and how often you pay for it

A HEPA layer handles particles — dust, pollen, dander, smoke. It does very little about gases and odours, which is what a separate activated-carbon or deodorization stage is for. The stage count hides that: the Airmega 200M lists deodorization as its own layer ahead of the HEPA filter, the ProX bonds carbon and HEPA into a single Max2 cartridge, and Levoit publishes the Core 300S-P as a three-stage original filter without enumerating the layers.

Stage count also sets the running cost, because a stage is a thing you replace. Coway lists 6 months for the 200M’s deodorization filter and 12 for its HEPA, and up to a year for the ProX’s Max2 — but a bonded cartridge is replaced whole, so there is no swapping only the spent layer. Levoit publishes no filter-life figure for the Core 300S-P, leaving the indicator on the unit as your only guide.

Noise range decides whether the thing gets used

A purifier too loud to sleep beside gets switched off at night, exactly when a bedroom unit earns its place. The range matters at both ends. The low figure — 22 dB for the Core 300S-P, 23 dB(A) for the ProX, 24.4 dB(A) for the 200M — is the sleep setting. The high figure is what you get when the unit ramps up, and the 200M’s 55.1 dB(A) is roughly conversation level while the ProX tops out at 46 dB(A) despite more than twice the CADR.

Matching the specs to your home

• A bedroom, and it has to be quiet — the low end of the noise range, then coverage at 4.8 ACH. Output you can’t stand to run is not output.
• An open-plan floor — CADR first, and check the coverage figure’s air-change basis before comparing anything.
• Cooking or pet odour is the reason you’re buying — a carbon or deodorization stage listed separately, since HEPA alone does not address gases.
• You want the running cost up front — published filter life, and whether stages are replaced separately or as one bonded cartridge.

Frequently asked questions

Do air purifiers actually help with allergies?

They reduce airborne allergens such as pollen, dust and pet dander circulating in a room. They do not remove what has already settled on surfaces or address the source, so they work alongside cleaning rather than instead of it. For that use the air-change rate matters more than the headline square footage.

How often do filters actually need replacing?

Manufacturers publish a figure — 6 to 12 months is the common band here — but it assumes typical use, and a purifier running constantly in smoke, dust or heavy pollen reaches the end of that window sooner. Where no figure is published, the unit’s filter indicator is what you have to go on.

Is a bigger, more powerful purifier always the better fit?

Not automatically, but oversizing has an easily missed benefit: a unit rated beyond your room hits the same air-change rate at a lower fan speed, so it runs quieter. What you pay is filter cost and floor space — the ProX is published at 51 lbs, a fixture rather than something you move between rooms.