User Guide
Table Of Contents
With a central furnace system, conditioned (heated or a/c) air blows out the supply
register, circulates in the room and then finds its way to the return air register where it
makes its way back to the furnace to be reheated or re-air conditioned after passing
through the furnace filter. A percentage of the particles in the air, such as mold spores
and other dust contaminants, get captured and removed from the air stream by the filters
Testing the furnace filter represents what contaminants have been circulating through the
house or zones serviced by the furnace.
Testing the furnace filter does not specify where the mold is coming from, but it is a good
initial screening procedure to determine if further investigation is warranted.
The return air side of the filter is the side of the filter test.


