Is it outside and raining?

Is there a cover over the fire? If you don't use an angled roofing piece to place over it then the fire will be exposed to the elements.

or if you have a cover, the cover could be too close to the fire and smothering it

I love the smoke mechanics in this game. They are just detailed enough to make it lively.

My first house was a ruin I found and patched up. Laid down a floor and couldn't figure out why I couldn't build a camp fire... well it was because i was trying to build a fire on a wood floor DUH

Got that worked out sat down to spend the night watching the campfire (didn't realize yet you could actually sleep in the bed) and because I had not built a chimney I gassed myself out of the house in the middle of the night.

Next morning I built a chimney... and it rained and put out my fire... Ah the lessons. :) Good game.