煙を出す means 'put smoke out', which is okay for some situations, but 煙が出る means 'smoke comes out', which is better for a lot of situations with smoke (like chimneys, which can't really be said to be 'putting' the smoke out... well, not literally, but you can say it anyway to create a certain imagery, in English or in Japanese.)
So 煙突から煙が出る means 'smoke comes out of chimneys', which is great if you're writing an encyclopedia entry about fireplaces. In descriptive writing though, you want to say 'smoke is coming from the chimney' which is 煙突から煙が出ている.
This can be contracted to 煙突から煙が出てる。
However, some dialects prefer おる in place of いる, and if you contract でておる you get でとる instead of でてる。