Respironics Millenium HEPA Inlet Filter

This is the plastic cartridge HEPA filter that is installed inside of the cabinet on the Millenium 5 liter oxygen concentrators.  It typically has a foam pre-filter installed on the inlet side.  Refer to the illustration below for details on how it is installed.  If your OPI indicator is alarming, a clogged filter could be the problem.

The inlet filter and the foam pre-filter are accessed by removing the panel cover on the back of the unit.

The inlet filter can be seen here with the foam pre-filter installed onto the top.  Both filters can be easily removed by simply lifting them up off of the inlet opening.