what happens if you breathe pure oxygen?

What happens if you breathe pure oxygen and why? Stephen, age 9, Muntinlupa City, The Philippines

Hi Stephen!

That’s a great question. We can’t live without oxygen. But too much can harm us. Let’s find out why.

Our bodies make the energy we need to run around, play and do schoolwork, by burning the food we eat. Think of this a bit like a candle burning. To burn our food, we need oxygen, which we get from breathing in the air around us.

Oxygen isn’t the only gas in the air. In fact, air’s mostly made of nitrogen. This has a very important job. Nitrogen slows down the burning process so you get enough energy through the day, bit by bit.

If you breathed pure oxygen, the energy from your food would be released all at once. So forget candles. This is more like a firework exploding. Bang! If you breathed pure oxygen, you wouldn’t actually explode. But you would damage your body.

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Breathing pure oxygen sets off a series of runaway chemical reactions. That’s when some of that oxygen turns into its dangerous, unstable cousin called a “radical”. Oxygen radicals harm the fats, protein and DNA in your body. This damages your eyes so you can’t see properly, and your lungs, so you can’t breathe normally.

So breathing pure oxygen is quite dangerous.

But breathing pure oxygen can sometimes be necessary. Astronauts and deep-sea scuba divers sometimes breathe pure oxygen because they work in very dangerous places.

The length of time they breathe pure oxygen, and how much they breathe, is carefully controlled so they’re not harmed.

Sick people, including premature babies in hospital or people in hospital with the coronavirus, might also need some extra help breathing. They might be given a bit of extra oxygen on top of what’s in the air. It acts like a medicine to help calm and settle their breathing.

Again, too much oxygen can be dangerous. That’s why doctors and nurses keep a close eye to make sure people get just the right amount they need.

So we need oxygen to help us get energy from our food. We might also need a little extra if we’re sick in hospital, or if we’re an astronaut or deep-sea diver. But too much oxygen can harm us.

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