Hydrogen car during automated refuelling with liquid hydrogen from a tank at Munich airport, Germany. The hydrogen is burnt in a type of conventional vehicle engine. Although nitrogen oxides are formed during the combustion, and carbon monoxide is created from vaporized engine lubricants, the main product is water. To keep the hydrogen as a liquid it is stored at -253 degrees Celsius in a tank with 70 insulating sheets of aluminium and fibreglass. For safety reasons, the hydrogen is pumped into the car by a robotic system. This car is made by BMW.