do not go for devices that have hepatype filters as it isnt rated to meet a hepa filtration level hepatype filters usually perform very poorly than actual hepa filters true hepa filters are also the real ones there are purifiers that have additional filters made of activated carbon or charcoal that trap gases odour compounds and volatile organic compounds vocs they are designed to take in only a specific number of compounds and need to be changed on a regular basis to be effective some air purifiers rely on ionizers or ultraviolet uv light which may also produce ozone which is a lung irritant that could make any breathingrelated problems worse rather than better and can be very harmful for our environmentenergy efficientair purifiers usually need to be running round the clock for the best impact which can be a factor for your electricity bills these devices also receive energystar certification as every other device uses different amounts of power depending on the fan speed it is using small air purifiers mostly use less energy than larger ones but large air purifiers with higher fan speeds pull more energy some air purifiers have builtin eco modes that power down the device and put them on standby when the sensors detect no pollutants there are devices that draw very low power while others that draw energy as high as 200w or more maintenance costthere are usually some maintenance costs after buying an air purifier you have to regularly replace the filters as and when needed the cost for replacing filters varies as some devices use expensive filters that will last longer while others use budget filters that have to be changed more frequently hepa filters are usually disposable and have to be replaced entirely while some prefilters are washable and can be reused calculate the cost every year you need to maintain and compare it with any other airpurification device you might consider before deciding on oneproducing less noisesome air purifiers have internal fans that pass the air through a series of filters most fans produce almost no noise at low settings but some start making humming noises as you turn them up for example if you are using an air purifier for your bedroom always go for the ones that are relatively quieter at higher speeds the specs of the device will reveal noiselevel ranges in decibels bonus features to considerthere are some bonus features available in some air purifiers like filter replacement indicator display dimming programmable timer remote control unit and smart functions digital assistant and app integration these additional features add to your convenience but these devices can be a bit expensive for having these features if budget is a concern you should always prioritise the above mentioned factors and can skip these bonus features