Before putting your Grayl away after an adventure, dry out the cartridge to prevent growth of mildew and odors. Thoroughly dry the cartridge by performing one ‘dry press’ by pressing the wet purifier into an empty (no water) Outer Refill and dumping excess water. Allow the cartridge to air-dry thoroughly (depending on humidity it will take 2-4 days to completely dry). Hand wash all other parts with warm, soapy water. For long-term storage, reassemble the unit to create an airtight seal for storage. Cartridges can last up to three years after opening if cared for properly between uses.