Terms "liquefied petroleum gas," "LP-Gas," and "LPG" that are synonymous and include any product composed predominantly of any of the following gaseous hydrocarbons: propane, propylene, butane, isobutane, butylenes, or a mixture thereof
NFPA 302 Fire Protection Standard for Pleasure and Commercial Motor Craft, 1998 ed. https://www.nfpa.org/assets/files/AboutTheCodes/30 2/302-A2003-rop.PDF, (Std: Fr Prac for Pleasure and Comm Motor Craft - Amer) {292 NFC}