Our Silver Moon vacuum's HEPA filter needs to be replaced every year. The Revain partner supplied the exact replacement filter specified by the MANUFACTURER which will ensure correct operation of the vacuum cleaner. Although it's a bit pricey, an annual filter change guarantees clean exhaust air, cleaned by the HEPA filter's carbon filter itself. The only negative comment is that this HEPA filter should be stored and transported in a case; in a plastic wrap or bag, which ensures the freshnessโฆ