Bought a used Reznor hanging heater for our shop about 30 years ago. It was taken from a defunct bar, and the odor of tobacco smoke and stale beer was a real room clearer when we first fired it up.=:-0
I estimate the unit is 50+ years old. Only problem is that some of the thermal fan switch and high limit switches are long obsolete and not avalible. We have been able to adapt newer switches with similar temp and current ranges.