Other specialized tankers include chemical tankers, liquefied gas carriers, and ore/bulk/oil carriers.
Chemical tankers carry various chemicals from port to port. Liquefied gas carriers transport natural gas and petroleum gas. These products are carried in a liquefied form rather than as gases because liquids take up less space than the same amount of gas. To maintain their cargo in liquid form, liquefied gas carriers hold cargo under pressure and at very low temperatures to prevent it from vaporizing. They are constructed of special types of steel that can withstand the stresses of pressure and cold. Ore/bulk/oil carriers, or OBOs, are versatile ships that can perform as tankers but carry several cargoes at once. The first OBO was put in service in 1985. Most are of panamax size, meaning that they are not too large to pass through the Panama Canal.