Unplug the purifier from the power outlet before opening the machine.
Unscrew the cap on the side of the purifier and remove the filter cover from the case.
Slide the old filter out of the unit and remove the pre-filter that is wrapped around the filter. The pre-filter can be used with the new filter. Dispose of the old filter.
Wrap the pre-filter around the new filter, slide it back in the purifier base and secure the cover on the base of the purifier.
Reset the filter indicator by pressing and holding the "Filter Monitor" button until the indicator light shuts off. You are now ready to use your air purifier as normal.