Old house with gas furnace but no filter question

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.
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Bob D.



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Bob D. wrote:

They don't necessarily come with the furnace. I didn't have a filter in my house either when I moved in. Had a Honeywell electrostatic added when the A/C was installed (SWMBO is a clean freak, insisted on either that or HEPA.)
nate
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The filter is probably supposed to go inside the lower part of the furnace.
Filters are pretty important.
JK
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If the house only has one large cold air return it may be in there and nowhere near the furnace.

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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

forced
critical
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