Astronauts need to sleep next to a ventilator fan while they’re in weightless orbit; otherwise, they might suffocate in their sleep. Reason being, is that warm air does not naturally rise when there is no gravity. And with no means of circulating this air, it is possible that the carbon dioxide we breathe out can form a bubble around one’s nose. Eventually, this will deplete the available air supply, which in turn, could be fatal.
