Nitrous oxide (N2 O), commonly known as laughing gas or happy gas, was first discovered in 1793 by the English scientist Joseph Priestly and has been used for more than 150 years. It has remained one of the most widely used anesthetics in both dental and medical applications. 
Nitrous oxide is small inorganic chemical molecule and may also be known as dinitrogen oxide or dinitrogen monoxide. It is a colorless and nonflammable gas with a slightly sweet odor. 
Nitrous oxide also has some illicit recreational uses and abuse potential. It is widely used in multiple nonmedical areas. Some of the nonmedical uses of nitrous oxide include the semiconductor industry, car racing, and food processing. 
Nitrous oxide is administered by inhalation, absorbed by diffusion through the lungs, and eliminated via respiration. The elimination half life of nitrous oxide is approximately 5 minutes.  It is excreted essentially unchanged (ie, nonmetabolized) via the lungs; less than 0.004% is actually metabolized in humans.