Gas, Fuel : A gas used as a fuel source, including natural gas, manufactured gas, sludge gas, liquefied petroleum gas-air mixtures, liquefied petroleum gas in the vapor phase, and mixtures of these gases
NFPA 820 Standard for Fire Protection in Wastewater Treatment and Collection Facilities, 2008 ed. http://www.nfpa.org/codes-and-standards/document-i nformation-pages?mode=code&code=820, (Std: Fr Prac in Wastewater Treatment and Collection Fcilty - Amer) {351 NFC}