My understanding is that a FILTRATOR is a CONDENSER dryer that uses room air to cool the closed internal-air circuit.
(Read: UNVENTED)
In a nutshell:
The same air is heated, blown through the clothes drum, picks up moisture, is cooled and condensed at the bottom of the machine and is then reheated. The cycle continuues ad-infinitum.
Of course really cold basements or garages work best for the condenser. Condenser dryers can use air or water to cool "the works" to achieve the necessary condensation. The FILTRATOR used cool/cold air from the room and returned it to the room warm (hot, really) but dry.
The heat is retained in the room but the moisture is not put into the room.
There is another thread discussing heat-pump condenser dryers (As opposed to an electric resistance coil supplying the necessary heat. You will note the internal air-circuit is the same..
air heated
blown over clothes
moisture condensed out (by cooling it)
begin again..air heated....
Indstead of usingair or water to cool the moisture-laden drum air, the heat-pumo dryer simply uses a cooling coil with a refrigerant ("freon" "Puron" or equivalent).
Hope this helps.