This filter with 2-layers of activated carbon pellets offers a level of defence against unwanted pet odours that can invade your home. Specifically designed to remove odours & VOC's this carbon layer is compatible with the Pet HEPA filter drum for all Leitz TruSens Z-1000 Small air purifiers. To keep your air purifier performing at its best it's recommended to replace the Pet carbon filter every 3 months (depending on usage)