Mr heater giving off smell stinging my eyes

I like mine. 80000 btu max propane unvented. I run it at 25k setting. I run a fan blowing down at an angle mounted on the ceiling to equalize the temperature from floor to ceiling. The fan keeps my floor fairly warm by forcing the heat down. I have a decent level of ventilation in my shop during the operation of the heater.

At night I leave a roof vent open and another cross flow open to purge the building.

I have zero issues period. I have no headaches, no one I know has issues being in the shop for hours. I have no unusual moisture issues either. I think the key is a decent ventilation during operation and leave the air vents open at night so the shop can exchange fresh air and dehumidify.