petroleum gases

Ethane, ethylene, propane, propylene, normal-butane and isobutane, butylene (butene) and isobutylene (isobutene), stored and transported as liquid under pressure. All have ignition points above 430°C (806°F) but extremely low flash points below -70°C (-100°F) and are non-toxic unless their concentration in air reaches 1000 parts per million (PPM). Also called refinery gases.