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From Slow Brains to Fast X, the Science Behind Nitrous Oxide
Live your life a quarter mile at a time... faster.
This weekend, audiences across the globe will return to the high octane adventures of the Fast Saga in Fast X. The tenth installment in the series comes from director Louis Leterrier and stars Vin Diesel (Dominic Toretto), Michelle Rodriguez (Letty Ortiz), and the rest of the extended Family, with appearances from franchise newcomers Jason Momoa (the film’s villain, Dante) and Brie Larson (Tess). That takes care of the Furious part of the equation, but we still need to account for the Fast. And for that, we’re going to need the other mainstay of the Fast Saga: Nitrous oxide.
WHAT IS NITROUS OXIDE AND WHERE DOES IT COME FROM?
Nitrous oxide is an oxide of gaseous nitrogen (obviously) with the chemical signature N2O. It is non-flammable on its own, which might be surprising given its use in combustion engines (more on that in a minute) but it likes to react, particularly with the ozone layer.
Nitrogen is the most abundant element in Earth’s atmosphere. It makes up more than 78% of every single breath you take. Oxygen might be the star of respiration, but it accounts for just less than 21%. The remaining 1% is mostly argon, CO2, and some other trace gases. The point is: There’s a lot of nitrogen floating around.
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That atmospheric nitrogen is taken up by nitrogen fixing bacteria in the soil and in the root nodules of plants. They convert the nitrogen into ammonia by adding some hydrogen. Then nitrifying microbes take the ammonia and convert it into nitrites (NO2) or nitrates (NO3). That is great news for plants because they love nitrogen compounds. Nitrogen is one of the main things we’ll need to add to the dirt when we start growing plants on the Moon, Mars, or elsewhere.
Plants grab those nitrates from the soil and use it to build some of their structures. That’s why leafy greens are such a good source of dietary nitrates. Those plants then get eaten or die and break down, either way, they eventually make their way back to the dirt where microbes get back to work, converting the nitrates back into nitrogen gas. This happens deeper in the soil, or deep under water, where oxygen is harder to come by and anaerobic microbes thrive. Along the path between nitrate and nitrogen gas, compounds pass through a number of intermediate gases, including nitrous oxide.
Nitrogen might serve as little more than a pressurized placeholder for your own respiration, but it’s an important part of the ecosystem’s natural infrastructure. Natural sources produce about 60% of the world’s nitrous oxide, every pound of which has 265 times the warming effect of the equivalent amount of CO2, and it stays in the atmosphere for an average of 121 years before being scooped up by bacteria again. The remaining 40% is the result of human activity, including commercial production.
Intentional production of nitrous oxide is an entirely chemical process, instead of a biologically facilitated one. Production begins with ammonium nitrate, a white crystalline salt — in chemistry, a salt is any compound containing positively charged and negatively charged ions, with no net electrical charge; table salt is a common example, but far from the only one — which is mixed with water at 80% - 93% concentration. The ammonium nitrate solution is then heated to 250 Celsius, which causes the reactive breakdown of ammonium nitrate into water vapor and nitrous oxide.
WHY DOES NITROUS MAKE CARS FASTER?
Combustion engines work by mixing a fuel source with air and lighting that mixture on fire. Every time you commute to work or drive to the theater, you’re doing so under the power of carefully controlled explosions. The fuel mixture is pressurized, and a spark is introduced. As the mixture rapidly combusts, it creates intense heat and pressure which moves the pistons in your engine. Those pistons turn a crankshaft which acts upon gears and so on, moving your vehicle down the road.
We think of gasoline (or whichever fuel you’re using) as the thing that’s burning, the thing that’s doing all the work, but that’s only partly true. Even the most flammable substance is powerless to ignite unless it’s up close and comfy with an oxidizer.
On Earth, whether you’re building a campfire or firing up your engines, the most common oxidizer you’re likely to encounter is, of course, oxygen. But it doesn’t have to be. When a fuel source is heated to the proper temperature, an oxidizer takes electrons from the fuel source. That rapid exothermic reaction is what we call burning. It’s just high-speed oxidation, like rusting in fast forward, and the reaction will continue until the fuel is consumed, the oxidizer is exhausted, or the temperature decreases.
If you’ve spent any time around an open flame, you know that blowing into a fire either with your own lungs or with a bellows is an effective way to increase the size and intensity of the flames temporarily. That’s because you’re adding more oxygen, which facilitates a higher rate of combustion. Since there’s no easy way to point a bellows at the inside of your engine, the proportion of oxygen in your fuel mixture is limited to 21%, because that’s what’s available in the atmosphere. It’s also why your car can become sluggish when operating at higher altitudes.
However, when a Nitrous Oxide System (NOS) introduces nitrous oxide into the fuel mixture, and it’s heated above 300 Celsius, it breaks down into one oxygen and two nitrogen atoms. As a result, the oxygen concentration in your fuel mixture is as high as 36%, considerably higher than the background 21% available at sea level. More oxygen means a higher rate of combustion, and more vroom.
OKAY, BUT WHY DOES NITROUS OXIDE MAKE YOUR BRAIN SLOW?
Nitrous oxide wasn’t really invented, but it was discovered and later synthesized by Joseph Priestly, in 1772. Before the 18th century was out, people were already playing with recreational and medicinal uses. By 1799, Humphry Davy had begun experimenting with the effects of nitrous oxide on humans, by inhaling the gas himself. He immediately noticed its euphoric effect and was reportedly so enamored of it, that he constructed an airtight box where he would sit for hours, breathing nitrous, to the point of almost dying.
Today, nitrous oxide is largely used in medical settings for its analgesic (pain relieving) and anesthetic effects. It is a time-honored addition to medical and dental environs, and the patron saint of root canal patients everywhere. It is favored because its effects are almost immediate, but short-lived. Doctors can relieve pain in near real time and patients are back up and functioning mostly normally within a few minutes.
While we know that nitrous oxide does work, scientists still aren’t precisely sure how it works, but we do have the basic framework and a few hypotheses. When inhaled, nitrous oxide enters the bloodstream by way of the lungs and makes its way to the brain. There, it triggers an increase in the natural production of endorphins, corticotropins, and dopamine. That’s likely what gives you the pleasant, euphoric sensation. Once in the brain, nitrous oxide also depresses sensation from all five senses and may prevent some of the brain’s emotional centers from functioning at max capacity.
It has been proposed that nitrous oxide might replace oxygen in the brain, causing some of its effects, but more study is needed before we’ll know for sure. Whatever the mechanism, the combined effects of nitrous oxide on the brain can slow or completely shut down some of the brain’s processes, allowing your dentist to drill into your face while you’re blessedly someplace else.
Perhaps, if your brain could heat the nitrous oxide to 300 Celsius, it might be able to use it to go really fast, but we don’t recommend it.
Fast X hits theaters this Friday, May 19. Get your tickets and start your engines!
