Gas and air is a pain relief method that uses a 50/50 mix of nitrous oxide and oxygen, inhaled through a mouthpiece or mask. It’s one of the most widely used forms of pain relief during labor and is also offered during certain medical and dental procedures. You control it yourself, breathing it in as needed, and its effects wear off within minutes of stopping.
What’s in the Mix
The medical name for gas and air is Entonox. Each canister contains exactly 50% nitrous oxide and 50% oxygen, compressed together. Nitrous oxide is the active ingredient, the same gas sometimes called “laughing gas” at the dentist. The oxygen half of the mix ensures you’re getting plenty of air while the nitrous oxide does its work. This fixed ratio is standard across hospitals, birth centers, and ambulances.
How It Reduces Pain
Nitrous oxide works on multiple systems in your brain at once. It triggers your body to release its own natural painkillers, the same type of chemicals that opioid medications target. The pain-dulling effect is comparable to morphine in how it acts on those receptors, though the overall strength is milder because the gas clears so quickly. At the same time, it activates a calming pathway in the brain that reduces anxiety, which is a significant part of why people find it helpful during painful or stressful procedures.
The net result isn’t that pain disappears completely. Most people describe it as taking the edge off: the pain is still there, but it feels more distant and manageable. You may also feel floaty, relaxed, or slightly euphoric.
How to Use It During Labor
Gas and air is self-administered. You hold the mouthpiece or mask yourself and breathe in deeply when you need it. This built-in safety feature means that if you inhale too much and start feeling drowsy, you’ll naturally let go of the mouthpiece and stop breathing it in. Within a few normal breaths, the effects begin to fade.
Timing matters. The gas takes about 15 to 30 seconds to start working, so the ideal approach is to begin inhaling roughly 30 seconds before a contraction starts. This way, the gas reaches its peak effect right as the contraction peaks, giving you the most relief when you need it most. Getting this rhythm right can take a few contractions of practice. Between contractions, you breathe normally.
One of its biggest advantages is flexibility. You can use gas and air at any stage of labor, in any birth setting (hospital, birth center, or home birth), and you can stop and start whenever you like. It can also be combined with other pain relief methods, including water birth or an epidural later on if you decide you need more.
How Quickly It Wears Off
Gas and air leaves your system fast. The pharmacological effects, the floaty feeling and pain relief, typically disappear within minutes of putting the mouthpiece down. Research on blood levels shows that the gas is eliminated in two phases: a rapid first phase with a half-life of about 2.4 minutes and a slower second phase with a half-life of around 31 minutes. In practical terms, you’ll feel clear-headed again very quickly, though trace amounts can be detected in blood for up to about two hours afterward.
This rapid clearance is one reason gas and air is so popular. Unlike injected painkillers, which can leave you groggy for hours, you return to your normal state almost immediately.
Side Effects
The most common side effects are nausea and light-headedness. These are usually mild and go away quickly once you stop breathing the gas. Some people also experience dry mouth, tingling in the fingers, or a sensation of being “out of it.” In clinical trials, side effects occurred more often with gas and air than with no pain relief, but none were serious and all were temporary.
A small number of people simply don’t like how it makes them feel. The dizziness or disconnected sensation can be unpleasant rather than helpful, and if that’s the case, you just stop using it. There’s no commitment involved and no lingering effects to wait out.
Safety for Mother and Baby
A review of the safety evidence concluded that nitrous oxide is safe for mothers, babies, and healthcare staff when delivered as the standard 50/50 blend and self-administered. It does not affect fetal heart rate the way some stronger pain medications can, and it has no known impact on newborn health scores. Because it clears from the bloodstream so rapidly, the baby is not exposed to meaningful levels of the gas.
UK guidelines from NICE recommend that Entonox be available in all birth settings. The guidance notes it may reduce pain in labor, while also advising that women be informed about the possibility of nausea and light-headedness.
How It Compares to Stronger Pain Relief
Gas and air sits in the middle of the pain relief spectrum. It’s stronger than breathing techniques or a warm bath, but less powerful than an epidural. A key question many people have is how it stacks up against injected opioids like pethidine.
A randomized controlled trial comparing nitrous oxide to intravenous pethidine (combined with a sedative) during gynecological procedures found that pain scores were not significantly different between the two groups, either during the procedure, immediately after, or 30 minutes later. Patient satisfaction was also comparable: about 83% of women in the nitrous oxide group reported being “very satisfied” or “most satisfied,” versus roughly 77% in the pethidine group. The practical difference is that gas and air wears off in minutes, while pethidine can cause drowsiness lasting hours and may cross the placenta to affect the baby.
Uses Beyond Labor
While labor is the most well-known setting, gas and air is used across medicine. Paramedics carry it in ambulances for trauma pain. Dentists offer it for anxiety during procedures. It’s used in emergency departments for setting broken bones, draining abscesses, and other short painful procedures. Urology and gynecology clinics use it for biopsies and minor operations where full sedation would be excessive.
In all these settings, the appeal is the same: it provides meaningful pain relief and anxiety reduction without sedation, needle sticks, or a long recovery period. You breathe it in, it helps, and a few minutes after you stop, it’s as if you never took anything.
Who Shouldn’t Use It
Gas and air isn’t suitable for everyone. Nitrous oxide expands trapped gas in the body, so it’s not recommended for people with a collapsed lung (pneumothorax), certain types of bowel obstruction, or anyone who has recently had ear or eye surgery involving gas bubbles. People with severe vitamin B12 deficiency should also avoid it, as nitrous oxide can interfere with how the body uses that vitamin. Your medical team will screen for these conditions before offering it.