Forced air system and no replaceable air filter?

[rokdar]

Greetings,

A house we recently moved into seems to have no accessible air filter element. The system consists of these two forced air blowers in the attic, each unit has a completely sealed intake box attached to it...if theres an air filter in there...replacing it would require me to slice the box open to actually check...if the boxes are removable from the blower units im at a loss of how to do it. The left unit has a single intake tube leading to a large vent while the unit pictured on the right splits into a few smaller intakes. Anyway, ive checked the large vent as well as tracked down the smaller ones and no air filter is to be found they are all just open vents

Has anyone ever seen/heard of a system that uses no replaceable air filter? Mabey some sort of electrostatic internal filter or something?

They are train units for what its worth, Ive attached pictures of the setup...sorry about the poor quality of the pictures

[HayZee518]

there may be an electrostatic unit inside your furnace. look for a narrow rectangular drawer on the outside of the unit near the exit air plenum.

[596]

Look for a main return air grill, which may have a filter in it. If you find a large grill with either some screws or flip tabs to open it up, the filter could be in there.