Rapid phase transition or RPT is a phenomenon realized in liquefied natural gas (LNG) incidents in which LNG vaporizes violently upon coming in contact with water causing what is known as a physical explosion or cold explosion. During such explosions there is no combustion but rather a huge amount of energy is transferred in the form of heat from the room-temperature water to the LNG at a temperature difference of about 175 kelvins.
Liquefied natural gas or LNG is a natural gas being liquefied at atmospheric pressure and -161.5 oC. It is odorless, tasteless, colorless, and not poisonous but causes asphyxia. It can cause frostbite due to its cryogenic temperature. If this extremely cold LNG is mixed with water, heat energy is transferred from water (sea water has an average temperature of 15 oC) rapidly and vaporizes it from the liquid state into the gaseous state and a phenomenon of rapid phase transition is resulted.