How Nitrous Oxide Works

Seventy years before Horace Wells began experimenting with nitrous oxide as a dental anesthetic, an Englishman named Joseph Priestly was on the verge of a series of momentous discoveries that would forever change our understanding of chemistry.

Priestly was one of the great Enlightenment thinkers, a contemporary of Benjamin Franklin and a prolific writer on every imaginable subject, from politics to religion to the nature of electricity [source: Chemical Heritage Foundation].

In the 1770s, Priestly turned his attention to the study of "airs," as gases were called in the 18th century. Living next to a brewery, Priestly had access to a nearly unlimited supply of carbon dioxide bubbling from the fermentation tanks. He adopted techniques used by Stephen Hales, who invented a device called a pneumatic trough to collect and isolate gases respired by plant leaves [source: Encyclopaedia Britannica].

With his own pneumatic trough, Priestly was able to isolate and identify eight gases — a research record that stands today — including oxygen (O2), nitrogen (N2), hydrogen chloride (HCI), sulfur dioxide (SO2) and nitrous oxide (N2O), or what Priestly called "nitrous air, diminished" [source: Zuck et al.].

It was another English chemist, Humphry Davy, who would shed further light on the mysterious properties of nitrous oxide. As laboratory superintendent of the Pneumatic Institute, Davy investigated the use of different gasses as curative therapies [source: Zuck et al].

In those days, self-experimentation was perfectly normal, and Davy thought nothing of huffing random gasses — including toxic fumes like carbon monoxide and carbonic acid — in search of scientific evidence [source: Watt].

In 1800, a presumably lightheaded Davy published a thick tome on nitrous oxide, but only made passing mentioned of its anesthetic properties, writing, "As nitrous oxide appears capable of destroying physical pain, it may probably be used with advantage during surgical operations in which no great effusion of blood takes place" [source: Zuck et al.].

It would be another 40 years before nitrous oxide was rediscovered by Wells and eventually accepted as a wonder drug for surgery.

The best-known uses of nitrous oxide are as a medical anesthetic and analgesic. An anesthetic causes a patient to lose touch with all sensation of pain — and often lose consciousness — while an analgesic simply lessens the severity of the pain. Tylenol, for example, is an analgesic.

Worldwide, nitrous oxide is the No. 1 inhaled anesthetic in the medical profession, always administered as a 50/50 blend of nitrous oxide and pure oxygen [source: Oglesbee]. As a patient in the U.S., you're most likely to encounter nitrous oxide at the dentist's office, but in Europe, Canada and Australia it's commonly used as a pain reliever during childbirth [source: ACNM].

The chief advantages of nitrous oxide as a pain reliever are that it delivers immediate and powerful analgesic effects and can be cut off just as quickly, with patients recovering full sensation within minutes of removing a nitrous inhalation mask [source: ACNM]. Emergency medical personnel use nitrous oxide for quick pain relief during a variety of medical situations, including heart attacks, severe burns, kidney stones, fractures and dislocations [source: Oglesbee].

So how does this gas work? When nitrous oxide is inhaled, the gas enters the blood stream through the lungs and travels quickly to the brain, where it triggers the release of the body's natural opioids, endorphins and dopamine [source: ACNM]. The anesthetic effect of nitrous oxide is achieved by temporarily stabilizing neuron activity in the brain [source: Oglesbee].

In the food industry, nitrous oxide is a highly effective propellant for dispensing fatty liquids like oil and heavy cream. To dispense whipped cream, nitrous gas is compressed into a liquid and mixed with heavy cream inside sealed, pressurized canisters. Because the liquid nitrous oxide displaces all oxygen in the can, an unopened canister of whipped cream will never go rancid. Nitrous oxide is highly soluble in fat, and when pressure inside the canister is released, the liquid nitrous instantly turns to gas, expanding the volume of the cream four-fold [source: Weingarten].

Another popular use of nitrous oxide is as a fuel additive in car racing. Read the full HSW article for all of the details on how an injection of nitrous oxide improves engine performance, but here's the gist: In an internal combustion engine, oxygen is critical for igniting the fuel injected into the engine. When nitrous oxide is heated to 570 degrees F (~300 C) — racing engines run hot — it splits into nitrogen and oxygen. Adding compressed nitrous oxide to an engine significantly raises oxygen levels, which translates to more fuel being burned and more horsepower [source: Hot Rod Network].

The final popular use of nitrous oxide is as a recreational drug. More on the "buzz" and adverse side effects of nitrous oxide abuse on the next page.

Centuries before buzz-chasing ravers sucked on balloons of nitrous oxide inside London dance clubs, there was Humphry Davy, the self-experimenting scientist who stumbled upon nitrous oxide's more pleasurable properties. Starting in 1799, Davy invited a growing circle of scientific colleagues, philosophers, writers and statesmen to partake of this euphoric gas during wild, late-night huffing parties [source: Watt].

Throughout the entirety of the 19th and early 20th century, the recreational use of nitrous oxide among high-society huffers was well-documented. Several early motion pictures were titled "Laughing Gas," including a 1914 short starring Charlie Chaplin as a prankster posing as a dentist.

In the 1970s, balloons filled with nitrous oxide (often just called "nitrous" on the street) began appearing at rock festivals and sold for 25 cents a pop [source: Wolfson]. Unlike the prolonged exposure preferred by Davy — in which the scientist experienced deeply hallucinatory revelations — a balloon full of nitrous delivers a numbing, swelling dizziness followed by the irrepressible urge to giggle.

In the U.K., where nitrous oxide is legal to possess for recreational use, 7.6 percent of young people ages 16-24 interviewed in 2014 said they had used nitrous oxide in the past year — about twice as many as had experimented with the popular club drug ecstasy or with cocaine [source: Wolfson].

Nitrous oxide is illegal to sell or possess in the United States for recreational use. But is inhaling N20 actually bad for you? Prolonged exposure to nitrous oxide will steal oxygen from brain cells, killing them in the process (apoptosis). The gas can also damage the protective covering of neurons called myelin, which may lead to long-term learning difficulties. But the real danger of huffing nitrous has little to do with brain chemistry — the most serious "side effects" are broken bones and head traumas suffered by people who fall down while buzzed [source: Go Ask Alice].