The gas dentists use is nitrous oxide, commonly known as laughing gas. It’s mixed with oxygen and delivered through a small mask that fits over your nose, producing a calm, relaxed feeling within two to three minutes. Nitrous oxide has been the standard inhalation sedation in dentistry for decades, and it remains the most widely used option for both adults and children.
How Nitrous Oxide Works
Nitrous oxide reduces both pain and anxiety by blocking certain receptors in your brain that process pain signals. At the same time, it enhances the brain’s natural calming pathways, which is why you feel relaxed and sometimes slightly euphoric during the procedure. You stay fully conscious and can respond to your dentist, but the experience feels distant and less stressful.
The gas is never given on its own. It’s always blended with oxygen, and the nitrous oxide concentration typically stays below 50% of the mixture. Your dentist starts at a low level and gradually increases it until you reach a comfortable state, a process called titration. Because nitrous oxide is absorbed into your bloodstream so quickly, adjustments take effect almost immediately, giving your dentist precise control over how sedated you feel throughout the appointment.
What the Experience Feels Like
Most people describe the sensation as a warm, floating feeling. Your limbs may feel heavy or tingly, sounds in the room can seem muffled, and time often feels like it’s passing faster than usual. Some people get mildly giggly, which is where the “laughing gas” nickname comes from, though not everyone reacts that way. You can still hear your dentist, answer questions, and breathe normally the entire time.
Once the procedure is done, your dentist switches the mask to 100% oxygen for at least five minutes. This flushes the nitrous oxide from your system and prevents a brief dip in oxygen levels that can cause headache or nausea. After that short window, the effects are essentially gone. Unlike oral sedatives or IV sedation, most patients can drive themselves home.
Side Effects and How Common They Are
Nitrous oxide has an excellent safety record. The most common side effects are nausea and vomiting, which occur in roughly 0.5% to 1.2% of patients. You’re more likely to feel nauseous if the concentration fluctuates, if the session runs long, or if you ate a heavy meal beforehand. Other occasional side effects include sweating, dizziness, headache, and restlessness.
A large French survey covering nearly 36,000 procedures, mostly in children, found an overall adverse effect rate of just 4.4%. The vast majority of those were mild: temporary nausea, brief agitation, or euphoria that resolved on its own. Serious complications are extremely rare when the gas is administered with proper equipment and monitoring.
Who Should Avoid It
Several medical situations make nitrous oxide a poor choice. If you’re in your first trimester of pregnancy, the gas can interfere with folate and vitamin B12 metabolism, both critical for early fetal development. People with severe heart disease face an added risk because nitrous oxide can raise homocysteine levels, which are linked to cardiovascular events.
The gas also has a physical property that matters: it’s about 30 times more soluble than nitrogen, meaning it rushes into enclosed air pockets in the body faster than nitrogen can escape. This makes it unsafe if you have a collapsed lung (pneumothorax), a bowel obstruction, or have recently had middle ear or certain retinal surgeries. Patients with severe psychiatric disorders are also generally advised against it, since nitrous oxide can occasionally trigger vivid dreams or hallucinations. Pulmonary hypertension is another contraindication because the gas can raise pressure in the pulmonary arteries.
Nitrous Oxide for Children
Nitrous oxide is particularly popular in pediatric dentistry. Children who are anxious, fidgety, or simply too young to sit still for a filling often respond well to it. The mask delivery avoids needles entirely, which removes a major source of fear. And because the effects wear off in minutes rather than hours, kids bounce back to normal activity quickly.
Interestingly, while nitrous oxide raises the risk of post-procedure nausea in adults by up to 20%, studies in children have not found the same increase when it’s used alongside other sedation. The main limitations in pediatric cases are practical ones: the child needs to be able to breathe through their nose and cooperate enough to keep the mask on.
Other Gases Used in Dental Settings
For most routine dental work, nitrous oxide is the only inhaled agent you’ll encounter. But in more specialized situations, particularly for patients with intellectual disabilities or extreme behavioral challenges, some dental anesthesiologists use sevoflurane. This is a more potent inhaled anesthetic that can induce deeper sedation quickly, sometimes starting at concentrations of 8% mixed with oxygen and nitrous oxide together.
Sevoflurane shares a few advantages with nitrous oxide: it’s absorbed and eliminated quickly, has minimal effects on heart rate and breathing, and doesn’t require an IV line. Its use in dentistry is growing in countries like South Korea, especially for pediatric patients and people with disabilities who can’t tolerate needle-based sedation. In the United States and most Western countries, though, sevoflurane in a dental office is far less common and typically requires a dental anesthesiologist to be present. For the vast majority of dental visits, nitrous oxide and oxygen remain the standard.
Safety for Dental Staff
One aspect of nitrous oxide that doesn’t affect patients but matters for the people who work around it: chronic occupational exposure. Dental assistants and dentists who breathe in trace amounts of the gas day after day face potential health effects over time, including disruption of vitamin B12 metabolism and, in some studies, reproductive concerns.
OSHA does not currently set a legal exposure limit for nitrous oxide, but the National Institute for Occupational Safety and Health recommends keeping workplace levels below 25 parts per million during procedures. The American Conference of Governmental Industrial Hygienists sets a slightly higher threshold of 50 ppm over an eight-hour workday. Modern dental offices manage this with scavenging systems built into the nasal mask that capture exhaled gas before it enters the room air.