NO is the chemical abbreviation for nitric oxide which is a chemical substance in the form of a gas. The gas is the part of the name represented by the oxide component which is said to be always containing 1 part oxygen and 1 part other chemical compound. The O of NO is representative of the oxygen compound. Nitric oxide is more commonly known as a pollutant that is air born which flows from machines that give of waste gases such as a combustion engine.

Nitric oxide is also found in humans and is a positive part of the bodies everyday functioning as well as a negative part of the human body. In small doses this gas is not harmful to humans as resides in our bodies to aid the transportation of messages through neural pathways that travel up and down the spine. The gas is also used as a means of communicating messages to the smooth muscle cells which are found in arteries and veins. The message to these smooth muscles allows them to relax which aids the flow of blood around the body.

Toxicity of nitric oxide can be known to cause some diseases and inflictions such as arthritis and diabetes in children. Opposing the relaxation of the arterial pathways an excessive amount of nitric oxide can cause the opposite reaction to arteries and veins by causing them to collapse.