N2O, or Nitrous Oxide, also known as laughing gas, is a weak anaesthetic (painkilling) gas that was first synthesised in 1775 by Joseph Priestley. Of the three early anaesthetics discovered (chloroform, ether and nitrous oxide) it is the only one still in regular use. While insufficiently strong for surgery, it was ideal for the lesser pain of dentistry. Unfortunately, it became popular as a scientific demonstration for public edification (and entertainment). The public entertainment aspect reduced its respectability and although it was first used in dentistry in 1844, it was not until the 1860s that it became more commonly used. Many famous people are recorded as having tried nitrous oxide.
Common uses of nitrous oxide include surgical, food service and recreational purposes. Many people have experienced nitrous as an anaesthetic for dental surgery. Nitrous oxide chargers are also used to make whipped cream. The dairy industry uses nitrous as a mixing and foaming agent as it is non-flammable, bacteriostatic (stops bacteria from growing) and leaves no taste or odour. Nitrous is sometimes used in auto racing to speed combustion. Nitrous is even used in diving to prepare divers for the nitrous-like effects of nitrogen narcosis. It is also a greenhouse gas emitted by fertilizer and implicated in global warming.
Given its myriad uses, it is not illegal to sell or possess nitrous. However, in the State of California the possession of N2O with intent to inhale is a misdemeanor: this is probably true of most states. One internet merchant was sentenced to 15 months in prison for selling nitrous with devices intended to facilitate its inhalation. The following is taken from the CA penal code:
381b. Any person who possesses nitrous oxide or any substance containing nitrous oxide, with the intent to breathe, inhale, or ingest for the purpose of causing a condition of intoxication, elation, euphoria, dizziness, stupefaction, or dulling of the senses or for the purpose of, in any manner, changing, distorting, or disturbing the audio, visual, or mental processes, or who knowingly and with the intent to do so is under the influence of nitrous oxide or any material containing nitrous oxide is guilty of a misdemeanor. This section shall not apply to any person who is under the influence of nitrous oxide or any material containing nitrous oxide pursuant to an administration for the purpose of medical, surgical, or dental care by a person duly licensed to administer such an agent.
You should check your State's Laws. When purchasing nitrous you implicitly agree to abide by the laws governing its use: the same as with gasoline, marker pens, white out, spray paint, ant poison, fabric softener, etc, etc, etc.
Physiological effects last a minute or two for a lungful of nitrous and then mainly dissipate. Some residual effects may last up to several minutes later. Unlike other drugs, the effects of nitrous very rapidly recede. As noted in 1845, "Those who inhale the Gas once, are always anxious to inhale it the second time." When inhaled, nitrous produces a variety of physical effects including:
The most common dangers from nitrous are due to its disorienting effects and the silliness that surrounds something called laughing gas. Tripping, falling or tipping over in a chair are very common. In one recorded case this caused death. The main cause of death from nitrous seems to be asphyxiation from a bag over the head. Frost bite from the very cold gas is also a concern, especially if dispensing when still disoriented.
Use common sense to avoid most problems.
Because nitrous permeates the lipid (fatty) membranes of your body, it can outgas into your gut or middle ear causing an ache. Cronic heavy usage has very unpleasant effects that could be permanent. Read more detailed dangers of nitrous use.
After several deep breaths of air, I inhale nearly a lungful of nitrous and pull some air down on top and then hold my breath. Within seconds, a light tingling can be felt which seems to increase in frequency. The sensation is much as if waves were traveling up your body or as if you were twisting or spinning. Disorientation increases rapidly and the pulsing sounds/feelings increase, wrapping over one another. It is now, with eyes shut, that I enter a dreamlike state, where I am thinking out something and the external world has essentially ceased to exist. The urge to breathe takes over at some point and partial or whole breaths taken. Open eyes reveal some sort of tunnel vision, with regions of disorientation about the outside. Slowly the throbbing subsides. At other times I experience a sense of paranoia mixed with disorientation. I have a deep conviction while under the influence that all things are cycling together, that there is some deeper cyclical event occuring. It is as an experience of deja vu continually occuring. The feeling is profound and not altogether pleasant.