An NFPA CNG Placard Sign on a fence in West Jordan, Utah, next to a CNG filling station.
The NFPA (National Fire Protection Association) rating sign for CNG (Compressed Natural Gas) follows the NFPA 704 Hazard Diamond system, which provides crucial safety information for emergency responders. This diamond-shaped sign is divided into four colored sections, each indicating a different hazard category:
- Blue (Health Hazard) – Typically rated 1 for CNG, indicating a slight hazard under normal conditions, but inhalation of high concentrations can cause dizziness or asphyxiation.
- Red (Flammability Hazard) – Rated 4, the highest level, as CNG is extremely flammable and can ignite easily in air.
- Yellow (Instability/Reactivity Hazard) – Rated 0, meaning CNG is stable under normal conditions and does not readily react with other chemicals.
- White (Special Hazard) – Usually left blank for CNG, as it does not have significant corrosive or radiation-related dangers.
These signs are commonly displayed on CNG storage tanks, fueling stations, and transport vehicles to warn of the gas’s high flammability and ensure proper handling during emergencies. Proper ventilation, leak detection, and adherence to safety protocols are essential when working with or around CNG.