system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is Helium, which doesn't undergo any reaction when used, a limited resource?
gpt
Many uses of helium cause it to escape into the atmosphere, where it escapes into space.

Unlike hydrogen (which also escapes the atmosphere, but is highly reactive and so is likely to bind with other atoms and thus not escape after all) it is also extremely rare to find on or in the earth.

These two things combined means that helium is indeed a limited resource.