It's not just propane. BlueRhino.com. NFPA Hazard Rating: Fire Hazard: Severe. Reactivity: Minimal. Extremely flammable gas. Heavier than air. Simple asphyxiant. Odorized to warn of its presence. Contact with liquid will cause freezing of tissue. PEL 1000 PPM. Store container outside and keep cool (under 180 degrees F). Turn off container valve when not in use. Personal Protection: Goggles; gloves.