How to choose the best air purifier

There are a lot of effective air cleaners out there that don't have the marketing budget of some of the big companies. So how do you choose?


1. Ignore the Marketing Hype


Claims about proprietary technology often aren’t backed up by independent tests. Also, don't be convinced by beautiful blonde families living in all-white homes. Read more about some of the premium options designed to help you part with your money.


2. Focus on the numbers


Clean Air Delivery Rate (CADR)


The most important numbers for an air purifier are the room size, which tell you how big a room the purifier can cover (when running on its highest setting) and CADR which tells you how much clean air is coming out of the purifier.


CADR has known flaws, but is the yardstick in which to compare the effectiveness of a purifiers. Some companies won't make this easy to find and will tell you what is wrong with the current system but in absence of a better (and standardised) form of measurement, this number is crucial to help you compare products on an equal footing. So unless your CADR is low, what is the harm in publishing it?


Some things to bear in mind when comparing CADR numbers:

  • There are two standards for measuring CADR. The American standard will measure smoke, pollen and dust and the Chinese standard will measure smoke/formaldehyde. To compare this equally, look for the lowest CADR which will be smoke.

  • Some companies erroneously add up all three to give you an extortionately high CADR rating

  • Most companies will only give you the CADR on high setting so do compare with the noise levels on high too or contact them for the CADR rate on other settings

Noise levels


If you’re looking for a quieter air purifier, choose one with a higher CADR number for your room size and then run it on low.


Compare purifiers using the clean air 'cost effectiveness calculator'


We have provided tools that let you calculate the the true cost of clean air and the number of air changes an hour you can expect for your room size. These will work with any purifiers, not just ours, so do use them before deciding which purifier to purchase.


3. Know that more expensive DOESN’T mean better


Don’t be fooled into thinking that more expensive purifiers are better. Turns out air purifiers are surprisingly simple – they’re just fans and filters. Smart Air (the manufacturers of our purifiers) started out making and marketing DIY purifiers using a fan and a filter. Here are the test results of two DIY purifiers (different fans, same filters) next to some big names...

DIY purifiers costing just US$30 can clean as much air as more expensive purifiers with their fancy claims. Read more for test data...


Find third-party test data


Not all purifiers have been independently tested but it is worth doing a quick search. If you are a paid member of Which?, check their data otherwise some data can be found on the Smart Air website