I, like many others living in old homes, have a basement smell issue. The house is old. How old? Don't know for sure (rent to own situation), but it's been here for at least 40 years.

The basement is very small. Concrete floor, cinderblock walls, halfway up. Not sure if it's the original set up or done after. For size, maybe 125 sqf? The ceilings are 6 foot. Anyways, the oil furnace is in the basement, as well as the 250 gallon oil tank. We don't have central air. There are also concrete stairs from the garage on one end (in addition to the wood stairs leading into the house) and then one small window opposite. That's all we have for ventilation, but leaving the door open to the garage isn't an option (cat) and the very small window (at ground level) doesn't open.

We have absolutely no water issues. I can run the dehumidifer all night and not have a drop of water in the machine. It's just the stale smell. The oil furnace doesn't smell much at all. If anything, I just smell musty (but not mildewy, if that makes sense) basement. It's not sewer or oil smells. We run on septic and I only smell oil when its delivered. The smell gets into the rest of the house and drives me insane, especially in the summer. It just seeps up.

I recently bleached the heck out of the basement. Sprayed and scrubbed the walls, ceiling, floors, everything. I left a huge fan running between the open door to the garage steps and dried it out. It smelled better immediately, but within a day, was musty again.

What sort of small Air Exchanger Ventilator system can I get? Money is an issue here. Is that even an option? This is my first old home with a basement.