Air purifiers: buying guide
Compare clean-air delivery, usable fan settings and replacement-filter costs without health promises.
Reviewed · Next editorial review by 5 February 2027 · Independent buying framework; no hands-on testing or product ratings.
Begin with the room and the reason you want an air purifier, then compare specifications for the settings you can live with. A large maximum room-size claim may be based on assumptions different from your own. This is an appliance-selection guide, not evidence that a particular device will prevent illness or resolve a medical condition. Keep ventilation and pollutant sources in the decision.
Which type suits your home?
Portable filter purifier
Check the exact filter combination and replacement codes. Compare the published clean-air delivery rate, or CADR, with the fan speed used for the noise and power figures.
Combined purifier and fan
Separate the functions you need and the data supplied for each. Air movement, filtration and any heating mode are different tasks, so one headline power number may not describe every operating mode.
Larger-room model
Assess the actual floor space, ceiling height and placement instructions. If a room-size claim does not explain its airflow assumptions, ask for the underlying specification rather than relying on the label alone.
What to check before buying
Comparable airflow evidence
Read which test measure and setting support the advertised CADR. Do not compare maximum clean-air delivery with the quiet-mode noise figure as if both happen at the same operating point.
Filter replacement basket
Find the exact replacement pack price and any stated replacement conditions. Availability matters as well as the upfront cost; an appliance with an unobtainable filter is difficult to maintain.
Controls and indicators
Check what the displayed sensor measures and how automatic mode behaves. A numerical display is not a full assessment of indoor air quality, and a filter indicator may depend on usage assumptions.
Placement and everyday noise
Allow the clearance specified in the manual. Compare the speed you expect to use during work or sleep, and check whether lights, beeps and app requirements can be controlled independently.
What ownership really involves
Use the electrical input for the intended fan setting and the hours you expect it to run. Include replacement filters in a separate ownership budget, because electricity alone can omit an important recurring expense. If the product includes heating or another function, calculate that mode separately rather than applying a low fan-only figure to all use.
A common comparison mistake
CADR is a performance measure under stated conditions, not a medical outcome. Do not infer that an air purifier substitutes for managing a pollutant source or following appropriate ventilation advice.
Compare running costs
A hypothetical 30 W operating mode used eight hours daily for 52 weeks. These are hypothetical starting figures, not a measured product average. Scenario B starts equal to A: change it to your alternative's documented figure.
Annual difference: £0.00. Equal under these assumptions.
Not a measured model or a health claim. Enter the chosen speed's input; filter costs and heating modes are excluded. Electricity only; excludes standing charges and purchase costs. Monthly figures spread annual cost over 12 calendar months. Seasonal estimate uses active weeks × uses per active week; 52 weeks is 364 days. A and B share the same usage assumptions.
Your questions answered
Can I compare two advertised room sizes directly?
Only if the underlying assumptions are comparable. Look for room volume, clean-air delivery and intended air-change conditions rather than treating every square-metre claim as the same test.
Does a low-power sleep mode give maximum performance?
Check the exact specification. Power, noise and airflow can depend on the selected setting. Compare figures for the same mode and avoid combining the best number from each mode.
Sources and evidence limits
Source links support the stated buying considerations. Manufacturer material is commercial information, not independent comparative testing. Our editable energy figures are hypothetical and are not taken from these products.
- ENERGY STAR: air cleaners and clean-air delivery rate ↗
US government technical explanation. CADR and recurring filter considerations only; US labels, certification and room-size advice are not presented as UK requirements. No medical claims adopted.
Check the current manual and product sheet for the exact model before purchasing. How we selected these 30 categories · Calculation methodology · Affiliate disclosure