The optional HEPA filter is a micro-glass paper mini-pleat filter which is inserted in a special housing (sold separately) mounted on the back of the Santa Fe Rx cabinet. The efficiency rating of this filter is 99.97% on the D.O.P. Test.
20" X 32" X 4" HEPA filter for Santa Fe RX - 99.976 Efficient at .03 microns (requires secondary housing)
The optional 95% efficiency and HEPA filters have long lives when prefitered by the standard pleated inlet filter; they can last many years in certain conditions. How long they last can, however, vary widely depending upon the following: Unit run time, air contamination level, and standard inlet filter cleanliness. Due to the optional filters' expense, it can be costly to change them prematurely. The following test helps determine when they should be changed.
Air exiting the bottom rear of the unit enters the filter frame, then passes through the optional filter and into the room. If the filter is dirty, air pressure builds up before the filter. To check this pressure, remove the plastic plug from the filter frame top; you will feel air coming out of the hole with the unit running. Place the ping pong ball that came with the filter frame on the hole and let go (any marked, regulation sized ping pong ball will work). If the ball does not move or only bounces slightly and does not spin continuously, the filter is clean enough for continued use. If the ball floats above the hole and starts to spin and perhaps wobble within 30 seconds, the filter needs to be changed.