For racing purposes, nitrous oxide is usually contained in an aluminum cylinder, and is available in a variety of sizes ranging from 2.5 lbs to 20 lbs. While retained in the cylinder, the nitrous is in a liquid form and held under high pressure. When its released from the cylinder into the intake tract, its physical state changes from a liquid to a gas. This transformation occurs as the nitrous is released from an area of extreme pressure (the aluminum cylinders are pressurized to approximately 1000 P.S.I) into the vacuum of the intake manifold. This change in state is usually referred to as the nitrous boiling. Water boils at 212 degrees Fahrenheit or 100 degrees Centigrade. However, if held under pressure in an automobile cooling system, for example, the coolant will remain a liquid, even above boiling point. Though inadvisable, if a radiator cap is removed under these conditions, and the pressure relieved, the water would expand and boil instantly. And so it is with nitrous oxide. While under pressure, nitrous exists in a liquid form. However when exposed to an instant reduction in pressure, the liquid expands and boils and the nitrous oxide is converted to gas. It takes energy to enable the nitrous to expand and boil. This energy is produced by the heat, which is absorbed from the surrounding air/gas in the intake tract. The end result is an intake charge that is cool, dense and oxygen rich - the ideal recipe for producing more power. The additional fuel required for nitrous is introduced in such a way that it is exposed to the full force of the expanding nitrous and it is atomized completely. This promotes improved burning in the combustion chamber and, as a direct result, power-output is increased. Nitrous Oxide (also known by the chemical formula N20) comprises two atoms of nitrogen and one of oxygen. The heat of the combustion breaks the chemical bond that holds them together. Without heat, the three atoms would remain bonded and, consequently, the oxygen atom rendered powerless, and unable to play its role in the combustion process. This is why inhaling nitrous can lead to asphyxiation, even though it has a higher oxygen content than air. Your body cannot produce the heat necessary (about 525 degrees Fahrenheit) to break the bond between the nitrogen and the oxygen, leaving the oxygen content useless for respiration. Gasses are often considered in terms of moles. The definition of a mole is the amount of substance that contains Avogadros number of atoms or molecules. Though this number remains the same (6.02 x 10 to the power of 23), the weight of a mole can vary depending on the atomic weight of the molecule in question. Because an engine requires volume instead of mass, weight can be dismissed. A mole of any substance occupies 22.4 liters at standard pressure and temperature. The fact remains that all gasses have the same molar volume in similar conditions. So, if a cylinder can draw two moles of air on an intake stroke, it can also consume the same volume of nitrous. By volume, air contains 21 % oxygen compared to nitrous, which is 50% oxygen. For every two moles of Nitrous Oxide (N20) introduced to the cylinder, there are two moles of Nitrogen (N2) and one mole of Oxygen (02), as can be seen in the equation below: