What goes up the chimney down, but can't go down the chimney up?

Answer 1

the answer must be an umbrella.
An umbrella is thin and narrow when it is down, so it can fit through the narrow opening of a chimney.
And when an umbrella is up, it is too large to fit through the same narrow opening.

so answer is 'UMBRELLA'.

Answer 2

Is it Smoke................
or Sunlight