Oxygen masks seem pretty straight forward – in case of emergency pull down, place over nose and mouth, tighten straps and oxygen will flow.
But did you know that it’s not actually oxygen?
They are there to help passengers breathe if a sudden loss of altitude leads to changes in cabin air pressure which could see people pass out.
But actual oxygen tanks are way too heavy and bulky to store in a plane so they use a complicated system and a host of different chemicals instead, reports News.com.au.
Stored in the overhead panel above each seat is a mixture of chemicals including barium peroxide, used in fireworks, sodium chlorate, found in weedkiller, an iron oxide or potassium chlorate.
In case of an emergency which sees the masks released, the chemicals activate each other and ‘burn’ and together they produce oxygen.
An occupational health expert at The University of Texas has said that is why there is often a dust like substance present, and the temperature increases in the cabin.
“It’s like turning on a new oven,” he told Huffington Post, saying it’s common to notice a burning smell.
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It comes after an image posted by a passenger on board the SouthWest flight, which suffered engine failure resulting in the death of one passenger, sparked a debate about the correct way to wear your oxygen mask.
Marty Martinez was heading home to Dallas when he heard two explosions and saw the masks drop. He then paid for Internet access, pulled up Facebook and began recording.
Mr Martinez's footage was quickly shared online and after the plane landed, many were quick to point out something wrong with the images.
Former flight attendant Bobby Laurie took to Twitter to remind travellers to always cover their nose and mouth with the oxygen mask.
"PEOPLE: Listen to your flight attendants!" Laurie said. "ALMOST EVERYONE in this photo from Southwest Air #SWA1380 today is wearing their mask WRONG," he wrote.
At least three people in the shot can be seen with masks covering their mouths, but not their noses, as instructed by flight attendants.
Some people have the masks fixed to their face using the oxygen mask band, while others are holding them up with their hands.
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