LNG is often mistaken for liquefied petroleum gas (LPG) or propane. While both fuels share some similar properties, there are distinct differences as well. Propane is heavier than air, while natural gas is lighter. Propane is typically stored under higher pressure, is contained in single-walled pressure vessels versus the double jacketed insulated vessels for LNG, is combustible with air at lower concentrations, and has a more volatile flame propagation.