Air purifiers work by drawing air through the machine and cleaning it as it passes through. They can remove minute particles like pollen, dust mites odours, bacteria and viruses.
What to consider:
Why do you need a purifier? If you need a purifier because you are an allergy sufferer and want to remove minute particles from the air around you look for one that uses a HEPA filter (insert link to allergy sufferer article). If you want to remove odours look for one that uses a carbon filter.
Size: Air purifiers are room specific so will only clean the room they are in. If you want to move it around you will need one that is portable. You can also buy car air purifiers if you want to clear the air in your car.
Noise Level: Choose an air purifier with low audible emissions or one that is silent. Noise is measured in decibels (dB) - 10dB is just audible while 40dB is a low level of ambient noise. An air purifier that seems quiet in a roomful of people may seem loud when you are trying to sleep. Some have different operating levels - silent, medium or maximum so you can adjust the noise level.
Cost of Operation: There main running cost with an air purifier is electricity and how much it uses depends on the size of the device, the speed it runs at and how long it is running for.
Another cost to consider is replacement filters. Look for one that uses filters that are guaranteed to last for a long time or with deodorising filters you can wash so you don't need to buy new ones.
Ease of use: Some purifiers come with sensors that monitor the contamination in the air and adjust performance to clear the room. Once the air is clear it will reduce its speed to a low setting. This means you don't have to change the controls and the purifier can be left to work on its own.
Filter Change Indicator: Useful to have so you are aware when the filter is becoming clogged and needs changing or cleaning.
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