Can someone hold their breath until they pass out? Understanding the body's override reflex

September 22, 2025 •

4 min read

While the world record for voluntary breath-holding is over 24 minutes, most people can only manage about 30 to 90 seconds. The question 'Can someone hold their breath until they pass out?' delves into the body's intricate, life-preserving mechanisms that prevent fatal self-suffocation through a built-in reflex.

Quick Summary

The body’s involuntary respiratory system will take over and force you to breathe again if you hold your breath long enough to lose consciousness. However, this reflex is not foolproof and comes with significant risks, including injury from falling or drowning if done underwater. The process is governed by carbon dioxide levels, not oxygen.

Key Points

The body's override: You cannot voluntarily hold your breath until you die because the brainstem's involuntary reflex will force you to breathe once you lose consciousness.
CO2 is the trigger: The overwhelming urge to breathe is primarily caused by the buildup of carbon dioxide, not the lack of oxygen.
Blacking out is not harmless: Fainting from oxygen deprivation can cause serious injury from falling or, if underwater, can be fatal due to drowning (shallow water blackout).
Hyperventilation increases risk: Breathing rapidly before holding your breath lowers carbon dioxide, delaying the warning signal and increasing the danger of a hypoxic blackout.
Children's spells are different: Breath-holding spells in children are involuntary, caused by emotional triggers, and generally harmless, with normal breathing resuming after the spell.
Extreme caution is required: Competitive breath-holding is extremely risky and should only be undertaken by highly trained individuals under strict supervision.
Brain damage is a risk: Prolonged oxygen deprivation from severe breath-holding can lead to brain damage, seizures, or cardiac problems.

The Body's Automatic Override: Why You Can't Voluntarily Suffocate

Your body possesses a powerful and life-sustaining defense mechanism that prevents you from voluntarily holding your breath to the point of permanent harm or death. The process is controlled by the respiratory center in your brainstem, which monitors the levels of gases in your blood. The primary driver for breathing isn't the lack of oxygen but rather the buildup of carbon dioxide (CO2), a waste product of your metabolism.

When you hold your breath, two things happen simultaneously: oxygen levels drop, and carbon dioxide levels rise. As the CO2 concentration in your blood reaches a certain threshold, it creates an overwhelming, involuntary urge to breathe, known as the 'breakpoint'. If you continue to resist this urge, your brain's protective instinct will ultimately win. You will lose consciousness from oxygen deprivation, at which point your voluntary control ceases, and the automatic respiratory functions take over, forcing you to start breathing again.

The Real Danger: When Passing Out Becomes Life-Threatening

While you won't die from voluntarily holding your breath in a safe, controlled environment, the act of passing out itself is incredibly dangerous, particularly in certain situations.

Injury from Falling: If you attempt to hold your breath until you pass out while standing or sitting without support, the resulting fall could cause serious head trauma or other injuries.
Shallow Water Blackout: This is an especially lethal risk. When holding your breath underwater, you can lose consciousness without warning. The involuntary reflex that forces you to breathe will still trigger, but it will cause you to inhale water instead of air, leading to drowning. This is a common and often fatal risk associated with underwater breath-holding games and competitive swimming.

The Peril of Hyperventilation

Some individuals attempt to increase their breath-holding time by hyperventilating first. Hyperventilating involves taking rapid, deep breaths to artificially lower the level of CO2 in the blood. While this does delay the onset of the powerful urge to breathe, it is extremely dangerous.

Here's why:

Delaying the Warning Signal: By lowering CO2, you are essentially turning off your body's early warning system. You feel like you can hold your breath longer, but your body is still depleting its oxygen stores at the same rate.
Hypoxic Blackout: Because the CO2 trigger is delayed, oxygen levels in your blood can drop to a critically low point before the urge to breathe becomes undeniable. This can cause you to pass out from a lack of oxygen (hypoxia) without the usual warning signs, making shallow water blackout a much greater risk.

The Science Behind the Urge to Breathe

Comparing the Drive to Breathe: CO2 vs. O2


Characteristic	Role of Carbon Dioxide (CO2)	Role of Oxygen (O2)
Primary Function	Waste product of metabolism; triggers the main respiratory drive.	Fuel for cellular energy; a backup signal for breathing when levels are critically low.
Sensing Mechanism	Monitored by chemoreceptors in the brainstem; sensitive to even small changes.	Monitored by peripheral chemoreceptors in arteries; less sensitive than CO2 sensors.
Effect of Accumulation	Rising levels in the blood create an overwhelming, involuntary urge to breathe.	Falling levels cause the body to shut down non-essential functions and, eventually, trigger a blackout.
Voluntary Control	Cannot be overridden by conscious thought for very long.	Less critical to immediate breathing regulation, making it a poor indicator for the average person.
Hyperventilation Impact	Drastically lowers CO2, delaying the signal to breathe and increasing danger.	Is not significantly impacted in the short term, but prolonged breath holding will lead to critically low levels.

Breath-Holding Spells in Children: A Different Mechanism

In children, particularly between 6 months and 6 years, breath-holding spells are involuntary, not a voluntary act. They are typically triggered by emotional distress, fright, or minor pain. A child may cry, hold their breath, and turn blue (cyanotic spell) before briefly passing out. While terrifying for a parent, these spells are generally harmless and do not lead to long-term health issues. The child's body will resume breathing shortly after they lose consciousness. Parents should remain calm and ensure the child is safe from injury during the spell, but medical consultation is warranted for recurring or atypical episodes.

Risks of Chronic or Competitive Breath-Holding

For the average person, there is no health benefit to practicing prolonged breath-holding. Professional free divers train for years to increase their capacity, often with the help of supplemental oxygen before a dive, but even they face significant risks. For example, a 2009 study noted an increase in markers indicating brain damage in trained divers after apnea. The extreme nature of the sport means it should only be performed under strict supervision. Competitive breath-holding is not a game; it is a dangerous activity that has led to fatalities.

For more detailed physiological information, consult medical resources such as the Scientific American article, "The Limits of Breath Holding".

Conclusion: Respecting the Body's Limits

While it is technically possible to hold your breath until you pass out, the body’s involuntary system prevents you from continuing until death. This protective override is a crucial aspect of human survival. However, the momentary victory of holding your breath long enough to faint is not without severe risks. The potential for traumatic injury from a fall or, worse, drowning from shallow water blackout, makes any voluntary attempt to pass out from breath-holding an extremely dangerous and ill-advised action. Respect the natural limits of your body and avoid engaging in breath-holding challenges or games, especially in or near water.

Frequently Asked Questions

Your body has a built-in reflex controlled by your brainstem that prevents voluntary breath-holding indefinitely. The buildup of carbon dioxide in your blood eventually triggers an overpowering, involuntary signal to breathe that you cannot ignore.

Shallow water blackout is a potentially fatal loss of consciousness caused by oxygen deprivation while underwater. It often occurs after hyperventilating, which delays the body's natural signal to breathe, causing a person to pass out and then involuntarily inhale water.

No, it is not safe. Even if not in water, passing out can cause you to fall and suffer serious injuries, such as a concussion or head trauma. The act itself also causes cerebral hypoxia, or low oxygen to the brain, which is never a healthy event.

Hyperventilation, or rapid deep breathing, artificially lowers the carbon dioxide levels in your blood. This delays the body's signal to breathe, which can cause you to run out of oxygen and pass out without warning, greatly increasing risk.

When you hold your breath until you pass out, your brain is being deprived of oxygen, a condition known as cerebral hypoxia. Your brain temporarily shuts down to protect itself. This can lead to lasting damage if oxygen is not restored quickly.

Children's breath-holding spells are involuntary and typically triggered by a strong emotional reaction, not a deliberate act. The child usually cries, holds their breath, and passes out briefly before normal breathing resumes. Unlike voluntary breath-holding, these are generally harmless.

Yes, it is possible. While a single, brief loss of consciousness is unlikely to cause severe damage, engaging in breath-holding for prolonged periods or under unsafe conditions (like underwater) can lead to serious hypoxia. This can cause brain cells to die, potentially leading to permanent neurological damage or even death.

For the average person, there is no health benefit to practicing prolonged breath-holding. Techniques like box breathing or rhythmic breathing can help with anxiety, but holding your breath for extended periods does not improve lung capacity or aerobic fitness and carries significant risks.