In the 1970s and 80s, soldiers stationed at Camp Casey, Korea, were allowed to have off-post facilities after written approval of the local commander. But, the facilities had to pass carbon monoxide inspections every six months if they were heated by ondol (charcoal or wood). A non-Commissioned Officer from the soldier's unit would prepare a film canister to hold a diesel soaked piece of cloth. The NCO would place the fuel-soaked rag on the top of the charcoal and close the heater. The black smoke would travel under the floor and exit the flue. However, any leaks in the floor would allow black smoke to seep into the room. This would be the same pathway that the deadly carbon monoxide would get into the living quarters, putting the occupants at risk. Certification of safe testing was the minimum due diligence on the part of command.