This catit magic blue air purifier is 25 times more effective than an activated carbon filter and is free from all chemicals as well as being easy to use it offers improved air quality in enclosed litter trays as well as in the surrounding environment and is entirely natural the small filter pads are in cartridges that your cat cannot access and can be easily attached to the top of the litter tray the pads absorb the unpleasant odours like a sponge rather than merely trying to mask the smel