system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does blowing air on a small flame put it out, but doing the same on a big fire only fuels it?
gpt
Fire requires three 'ingredients' to take place: fuel, oxygen, and heat (let's make a basic assumption that we're talking about a wood fire so we don't get into critters like magnesium, other oxidizers, etc.).  If you direct a stream of air towards a fire one of two things will happen:

* the fire will consume the air and enlarge in size
* the air stream will interrupt the reaction; i.e. cooling the temperature to below what's required to continue, etc.

It's really a question of scale.  For a particular sized 'fire', the ingredients must be in the proper proportion.  Outside those proportions fire can't happen.