LOW AIR PRESSURE IS AN EVER-PRESENT DANGER

Humans are built for our atmosphere… remove it and we’re in trouble

Lack of oxygen will kill you, but a lack of pressure is no fun either. Our bodies are ‘pressurised’ – we can measure this as blood pressure. This counteracts the huge pressure of the weight of the atmosphere pushing down on us. But if that atmospheric pressure is removed, a number of things will happen.

First, gases within body cavities will expand rapidly, the most damaging of which would be in the lungs. If the decompression is quick, breath can’t escape out of the windpipe fast enough and will burst through the walls of the lungs into the thoracic cavity. This would turn the lungs to mush, but is unlikely to mean the body explodes, as is often said. The trick is not to hold your breath, which would mean almost instant death.

Under decompression, your bodily fluids will begin to turn into vapour, which is called ‘ebullism’. Bubbles of gas will develop quickly throughout the body, causing you to swell up like a balloon – although again you are unlikely to explode. A common misconception is that this results in the blood ‘boiling’, but because blood vessels exert an elastic pressure, the blood’s boiling point will remain above body temperature – at least as long as the heart is still beating. However, fluids in direct contact with the vacuum of space will begin to boil, so the eyes and tongue will start to bubble.

If you’re caught in the vacuum of space without your oxygen supply or pressure suit, rapid deoxygenation of the blood will cause a loss of consciousness within about 15 seconds. After 90 seconds or so, death is inevitable, although your heart may continue to beat for up to four minutes.