Man shows why you should never run into empty caves as air inside could be deadly

A man has demonstrated why you should avoid running into an empty cave.

It might not seem like something you would instinctively want to do, but just in case you do get the urge to Leeroy Jenkins into one, this is something you should bear in mind.

It's no secret that caving can be a dangerous business, particularly when caves get extremely narrow to the point that you have to manipulate yourself through them.

But getting stuck in the actual physical spaces is not the only risk that comes with going into a tight space underground.

When you have small spaces which are isolated from the surface they can create their own environments.

You're probably familiar with the old technique of miners carrying a canary in a cage underground.

If that doesn't give it away, then let me explain.

Canaries were used as an indicator for if there was gas present - if the canary died, get out fast.

But the reason this is needed is because there are pockets of gas underground which could be extremely dangerous to humans unlucky enough to run into them.

And while mining increased the risk of this, you could also encounter a gas pocket in a natural cave.

The big danger is that carbon dioxide is heavier than air, meaning that it can sometimes 'flow' down into caves and gather at the bottom.

Running into one of these 'pools' of carbon dioxide can be deadly, as it doesn't take much of the gas to render us unconscious.

And then once you collapse on the floor into the gas, you're done for.

The video shows how this can happen as the man holds a flaming torch inside a cave.

It's fine at the top. (Reddit/ternera)

This deadly cave is located in Costa Rica, South America, on the edge of the Poas Volcano and people are strictly prohibited from going in.

According to The Costa Rica Star, it is only small - measuring just two meters deep and three meters long.

In the clip, the man puts the flaming torch inside a cave where there is oxygen, but then as soon as it hits the layer of carbon dioxide at the bottom the torch immediately goes out.

It's so abrupt it's like an invisible hand has pinched out the flames.

Despite being too deadly to actually enter, the cave is still a popular tourist attraction, called 'Cueva de la Muerte' (Cave of Death in Spanish).

Imagine if you had tried to crawl in there with your head at ground level. (Reddit/ternera)

Caves are not the only place where a build up of carbon dioxide can be a danger.

The holds on cargo ships can also see a dangerous buildup of carbon dioxide, especially when transporting certain cargos.

One such cargo is pistachio nuts, which excrete carbon dioxide. So having a load of them packed into a ship's hold could mean a deadly buildup of the gas for any sailors that go down there.

Oh also, unprocessed pistachios can explode.