YOU WERE BURIED ALIVE

Once you’re placed in an airtight coffin you’d start using up its oxygen. A typical coffin has 900 litres of air and you take up 80 of it, so you would have 820 left.

Your lungs take in half a litre a breath, but you use up only 20% of the oxygen for each breath – meaning you could rebreathe the same air a few times before depleting it.

Of course, you wouldn’t need to breathe every last bit of oxygen before running into trouble. Air is 21% oxygen and that’s where you’re happy.

Once you began using up oxygen you’d quickly run into issues: headaches, dizziness, nausea and confusion as your brain cells began to starve. Your coffin has enough oxygen to last around six hours before you start to asphyxiate – as long as you stay calm.

You’d think that you’d last longer holding your breath, but that actually increases your oxygen usage when your body overcompensates for the carbon dioxide (CO₂) build-up with bigger breaths than it needs.

Slow, controlled breathing is the way to go. Once the oxygen drops to 10% you’d go unconscious and quickly fall into a coma. Sudden death happens at 6-8% oxygen.

And there’s another issue competing to kill you. By breathing, you’re replacing the oxygen in your coffin with CO₂. That’s a problem. The excess CO₂ binds with your blood and limits the amount of oxygen it can carry into your tissues – effectively asphyxiating your vital organs and poisoning your central nervous system, which would manifest as confusion and delirium.

So perhaps you’d see a ghost in your coffin ...