TruSens - Replacement Activated Carbon Filter Allergy & Flu Filter Drum. This filter with activated carbon pellets provides a protective barrier against unwanted odors and volatile organic compounds (VOCs) that can enter your home. This carbon layer has been specifically designed to remove these pollutants from the air and is compatible with the Allergy & Flu HEPA filter drum. To ensure optimal performance of your air purifier, it is recommended to replace the Allergy & Flu activated carbon filter every 3 months (depending on usage duration). This activated carbon filter is a replacement part for the Allergy & Flu HEPA filter drum. The replacement indicator will light up red on your air purifier when the filter needs to be changed. For best cleaning results, it is advised to replace the Allergy & Flu activated carbon filter every 3 months (depending on usage duration). Ideal for combating allergies and flu. Package includes: 1 x activated carbon filter.