Unplugging the device using the filters, taking off the cover and prefilter, discarding the old filter and putting the new filter in are the major steps involved in replacing HEPA filters. These high-efficiency particulate air filters are found in many vacuum cleaners and household air purifiers.
Turn the vacuum cleaner or air purifier off, and pull the power cord from the wall. This protects the machine from damage and you from electric shock. Set the unit on a plastic tarp or some old newspaper to keep debris from making a mess.
Take the cover off the filter, following the directions in the owner's manual. Some require owners to remove screws, while others snap off. Vacuum cleaner covers are usually by the bag or canister, while air purifier covers are by the system's base. Take the prefilter out, and vacuum it if there is a lot of dirt, or rinse it with cool water, if the owner's manual indicates. Do not put it back in until it is completely dry.
Take out the old HEPA filter, grabbing it by the edge if flat or the outside cover if round. Put it carefully into a trash bag to keep dust from spreading. Slide the new filter in, mounting it securely. Put the prefilter back in place, using arrows on it as a guide, if applicable. Replace the cover, and plug the machine back in. Turn the system on to test its performance.