Gas, Sludge : Gas obtained as a by-product of the anaerobic sludge digestion process from the decomposition of organic matter in biosolids in liquid or semi-solid state when stored for extended periods of time
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}