In general it is recommended that you replace your disposable filters at least once a month. If you have washable filters, they should be cleaned once a month. A service technician will recommend a replacement schedule that delivers the optimum efficiency and filtration for your specific system., we clean and inspect your HVAC system twice each year. Part of the service includes changing the filters or servicing your filtering system. Unless you have special circumstances, our service should be adequate. We recommend that you visually check filters and filtering equipment monthly. If filters look dirty, they need to be cleaned or replaced.