We recently purchased a home with a trane air handler in the attic and a york heat pump outside. The age of the trane air handler is easily 25+ years old. When I attempted to locate a filter for the air handler there doesn’t appear to be one? (I have a similar set-up for my business which is much newer that has a replaceable air filter for the air handler.) In our new home there are multiple returns throughout the home with replaceable air filters. Considering the age of this unit is it possible that there wouldn’t be an air filter for this unit in the attic, and just the filters in the home?