I don’t get this, but I see it all the time. Why would they put a return next to the furnace?
To kill your family?! …
It is an oil-fired furnace, so it’s unlikely (not impossible, just unlikely) that it would pull exhaust back into the system. I see it quite often.
They just don’t now about building science and interior house pressures. They have been lucky probably because the house envelope is quite loose and the furnace operates on short cycles (oversized). A few years back in my area, there was a CO death from an oil furnace.
You should mention this in your reports!
I am assuming you are seeing this in “conditioned” basements? If it has a supply, it will also have a return. I bet you just aren’t seeing the supply.
The supply was in the next room. There was no supply in this room.
And I’ll bet there was no return in that room. It’s a basement, right? Hopefully the door was cut or louvered to allow for return airflow.
Case closed. 
LOL - case closed!
No return in the same room, or within 3’ of the furnace. Just plain common sense, as well as part of the national gas code.
Nuff said.
I call that out all the time.
Had that safety issue yesterday as a matter fact.Strange thing was they had extra air tubes for makeup air when the utility closet was large enough to not really need them.
I write it up as safety hazard if within 10’ from the furnace in open basement or if in same room as furnace.
Oil fired furnace Will
In order for air to return from the remote room, a pressure differential is needed. In this case, the furnace room will be under a negative pressure in relation to the other room and possibly backdraft the chimney through the barometric damper (oil)/draft hood (gas) if a strong chimney draft has not been established.
The negative pressure extends throughout the room!
You’ve never been in a Minnesota basement have you? :shock:
No matter how many times you do it wrong, it will never make it right. David Andesen
Even if I think a damper is acceptable I would still make the call to have a HVAC tech approve it.