system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does mold get into the fridge/my house if it wasn't already there?

I know mold spores can travel through the air, but what about when I put food in my fridge with nothing moldy in there, no mold in the house... Eventually it is going to turn moldy. How?
gpt
There *is* mold there, you just can't see it. You said yourself that you know that mold spores spread through the air - that's your answer. Mold spores are absolutely everywhere. It *was* already there.