Bedroom
Check performance at the fan speed you could actually sleep with.
Cleaner indoor air
Compare air purifiers by airflow, filtration and lifetime cost
Room coverage claims are not enough. Compare clean-air delivery, filter type, noise at useful speeds and replacement-filter availability.
Identify what you want to remove
Write down the particular concern before comparing products: airborne particles, cooking-related pollution or another source. An air purifier is not a cooling appliance, a damp repair or a substitute for addressing the source. The US EPA's consumer guide is useful for filtration principles, not UK product certification: it distinguishes particle clean-air delivery from gas-removal claims and warns against intentionally ozone-producing devices. Do not turn a filter specification into a promise to prevent illness.
Request the missing room-coverage assumptions
Measure length, width and ceiling height. If a listing gives only a floor area, ask which ceiling height, fan setting and air-change assumption support it. Record the CADR units so cubic metres per hour are not compared directly with cubic feet per minute. A headline CADR and a quiet-mode noise figure may describe different settings. The EPA notes that reducing fan speed reduces the amount of air filtered; compare the useful operating setting, not two unrelated best-case numbers.
Check the replacement-filter purchase before ordering
Find the exact replacement-filter code and a supplier that serves your address. Record its price and the manufacturer's replacement guidance without assuming the filter will last a fixed time in every home. Ask whether a pre-filter is washable and which parts must be replaced; follow the particular manual rather than washing a filter because it looks reusable. Put equipment, replacement consumables and electricity on the same ownership-cost worksheet. Also check access for filter changes, light dimming and the controls you will use daily. A cheaper machine can be an inconvenient choice if the required consumables are difficult to obtain.
Guidance checked . US EPA: guide to air cleaners (filtration principles) ↗
Choose your route
Start with the type of outcome you need
Living space
Match clean-air delivery to room volume rather than marketing room size alone.
Allergy support
Review filter specification and replacement schedule without medical promises.