How to get rid of this?

[lebmung]

How did you find out it ran out of oxygen?

It was an emergency day so I put a burner inside and and burn the gas. It consumed all oxygen then the flame ran out so the gas kept flowing. The whole greenhouse was full of gas, like a bomb which was waiting for a spark. Fortunately nobody smoked around. 

[brian]

Scary.  I was very worried about this when I started with gas heaters but even after running propane all night in a small area it was fine.  Must have been leaking enough to keep new air coming in.