This filter with 3 layers of activated carbon pellets offers an unprecedented level of defence against unwanted odours in your home. Specifically designed to help combat common cooking and cleaning odours, and reduce airborne VOCs such as ammonia, acetone and formaldehyde, this 3-layer carbon pellet filter is compatible with the Odour and VOC HEPA filter drum for all Leitz TruSens Z-3000 / Z-3500 Large air purifiers. To keep your air purifier performing at its best, it's recommended to replace the Odour & VOC carbon filter every 3 months (depending on usage).