Old Lennox furnaces had cradle like basket in the lower compartment (under
the burners), which used filter material that came on a roll. You wrap the
filter material around the basket.

RichK

"Bob D." wrote in message
. ..
A friend of mine just moved into a small older house. It has a small
forced
air gas furnace (Carrier brand), that I'm sure was retrofitted at some
point. For the life of me, I can't find a furnace filter. Did they not use
air filters in the old days? I just want to make sure this isn't a
critical
component.