Why blowing slowly on a fire makes it grow, but blowing fast can put it out?

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Not sure if this is actually a chemistry question so excuse the flair if it’s wrong. I’ve heard that blowing slowly on a fire introduces more oxygen into it, which is needed to grow the fire. But don’t we breathe out carbon dioxide???

And when you blow quickly, I suppose you’re separating/distributing the embers but I need someone to confirm this and elaborate further.

In: Chemistry

3 Answers

Anonymous 0 Comments

Common misunderstanding.

Air we breathe in: 78% nitrogen, 21% oxygen, 1% argon.

Air we breathe out: 78% nitrogen, 17% oxygen, 4% carbon dioxide, 1% argon. [Source](https://byjus.com/biology/composition-gases-breathe/)

Still lots of oxygen in an exhale, more than 4x more oxygen than carbon dioxide. When you hear “humans breathe out CO2” it means “humans breathe out all the CO2 that their bodies make” not “everything they breathe out is CO2”.

Back to your question: Fire needs heat, fuel, and oxygen. Blowing slow = adding more oxygen (exhale is still 17% oxygen and only 4% CO2!) Blowing fast = removing too much heat or fuel.

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