Yes, the filters do need replacing. The effective working life of Respro filters depends on a number of factors, such as; the breathing rate of the user; ambient levels of pollution; the length of time the filter is actively working; hygiene levels. Taking these factors into account we recommend that the filter should be replaced every month or every 69 hours, whichever is sooner. Replacement of the Sportsta filter should be carried out every month or when the filter becomes noticeably discoloured.