Even the most efficient propane heaters produce gas fumes. It's always a good idea to place your heater in a well-ventilated space where fresh air is continually introduced, and any fumes the heater produces can disperse harmlessly.
While propane heaters we feature are considered safe to use indoors, we still recommend allowing fresh air for ventilation. Many propane users crack their service or garage door a couple of inches to allow some fresh air - and in many cases - to cool the garage down.
Radiant heaters typically do not require additional ventilation.
Kerosene heaters that operate on Kerosene or Diesel Fuel require fully open ventilated spaces to be used safely.