As a parent, I often find myself asking questions I never thought I would ask: How long can someone survive on raisins alone? How did that yogurt get on the ceiling?

And so one night, after carefully placing my sleeping baby down in his crib, I stood there holding my breath, noting that I would obviously choose passing out over possibly making the slightest sound that could wake him. I wondered, How long can a person’s body go without oxygen? What sets that limit and why is it that some people can hold their breath for minutes but others only seconds?

To set the Guinness World Record for breath-holding, a professional freediver went without breath for a whopping 24 minutes and 3 seconds.

The Guinness World Record for the longest time spent holding one’s breath was set in 2016 by Aleix Segura Vendrell in a pool in Spain. The professional freediver went without breath for a whopping 24 minutes and 3 seconds. Before Vendrell, a record was set just two years earlier in 2014 by Danish freediver Stig Severinsen at 22 minutes. Those numbers are more than 40 times longer than the 30 seconds or so that the average person goes before coming up for air. Compare that to the fastest mile-run on record at an impressive 3 minutes and 43 seconds which is only 3-4 times shorter than the more average pace of a 12-minute mile.

Hyperventilating allows you to hold your breath longer

When you hold your breath, it’s not actually the lack of oxygen that does you in, but the excess of carbon dioxide that is not getting exhaled. When CO2 builds up in your body, your blood will acidify as your enzymes convert water and the excess CO2 into carbonic acid. This acidification can lead to drowsiness and headaches and ultimately have a detrimental effect on the body’s major organs.

One way record-breaking breath-holders manage such long stints under water is to breathe pure oxygen (basically hyperventilate) before their diving attempt.

So one way record-breaking breath holders manage such long stints under water is to breathe pure oxygen (basically hyperventilate) before their diving attempt. This rids their lungs of as much CO2 as possible.

If you take a deep breath right now and try to hold it, you may notice that exhaling a bit helps you hold it longer.

Throughout Vendrell’s 24 minutes, the oxygen in his lungs got picked up by his bloodstream to be distributed to his vital organs. Without oxygen and without CO2, his lungs were empty so he was able to stay under and only inhaled deeply after rising above the surface.

Does lung capacity set a limit on breath-holding?

This suggests that lung volume or capacity may set a mechanical limit on breath-holding. So those with longer torsos may be at an advantage. Men also have higher lung capacities than women by 10-12% likely due to larger on average rib cages.

Lifestyle choices like not smoking and endurance training can increase your lung capacity, but usually only by incremental amounts.

Freedivers employ a technique called lung packing that can double or even triple your lung capacity. When lung packing, you fill your lungs with air but then continue to take smaller breaths, effectively forcing them down into your already full lungs and training your lungs to hold more air.

However, it’s not all mechanics. Your metabolic rate does factor into how long you can hold your breath. That’s why record-setting breaths are taken while floating in a pool and not while someone is actively swimming or diving.

The limit may be psychological

However, even given extensive training and massive lung capacities, researchers still don’t see a clear explanation for how someone can manage going over 20 minutes without air and suggest that it can’t be all physiology. There must be some form of mind-over-matter involved.

All mammals have what is called a dive reflex which causes our hearts to slow down when we submerge our bodies or even just our faces in cold water. This reflex is why these long stints of breath-holding happen in pools. Our blood gets redirected from our neglectable extremities to focus instead on our more important organs like the brain, heart, and lungs.

The dive reflex has saved the lives of more than a few people who have fallen into icy water for several minutes before being rescued.

All mammals have what is called a dive reflex which causes our hearts to slow down when we submerge our bodies or even just our faces in cold water.

So what does a reflex have to do with psychology? Many freedivers describe entering a calm and meditative state as a key tool for holding their breath for extended periods. They are able to extend the same benefits of this dive reflex through training and practice.

Another huge psychological factor is overcoming the urge to breathe. It sounds simple, but our instinct, luckily, is survival. So the urge to breathe—that chemical signal our body sends to the brain screaming “I need air!”—may be more important in sending us back to the surface gasping for air than the actual need to breathe. Freedivers like Vendrell describe fighting that urge as a key tool for keeping themselves underwater.

So scientists don’t yet understand what exactly sets the human body’s limit on holding its breath, but it is likely a complex combination of mechanical, metabolic, and psychological factors. Advances in pushing the known limit appear to progress similarly to other feats of athletic prowess, that is, not linearly. In other words, each new record no longer doubles or triples the previous one, but instead advances appear to be leveling off and becoming more incremental with each new record-setting breath.

And if you’ve held your breath throughout this entire podcast, congratulations—you only have to extend that by about four more times to be the next record-holder!