Check the Honwywell web site. But what we told customers was the core needed to be removed about every six months and washed. Some people put them in the diswasher but don't bend the wires. If you have a utility sink they will fit in use a mild detergent let them soak and then rinse and dry thoroughly. The prefilters need also to be cleaned. If they have activated charcoal in them do not wash. They will need to be replaced but not every six months.