Natural & propane gas in itself isn’t poisonous. Gas burners that aren’t adjusted properly or vents that are not vented properly can produce carbon monoxide. Carbon Monoxide is an odorless, tasteless, non-visible gas that can be formed when fuels like charcoal, coal, gasoline, kerosene, natural or propane gas, oil, or wood are burned without a sufficient supply of air. Carbon Monoxide can be produced when appliances are not properly installed, maintained or used; when vent pipes become plugged with debris; when vent pipes have gaps, leaks, spaces and rust-through spots; and when appliances are improperly vented (All vented type appliances must be properly vented to the outside). Exposure to carbon monoxide poisons the body and can cause collapse or even death. Symptoms may include headaches, dizziness, and nausea.