They put poison inside, in the holder. When they got hot, they expanded, when that happened then the gas came out. It's quite neat.
12 seconds sound clip from the The Kid with the Golden Arm movie soundboard.
You can hear this line at 00:45:38 in the DVD version of the movie.
Quote context
[...]
- I am not a drunk like you are.
- Drinking wine can have its advantages. I've been drinking the whole day.
- Hey it's the rings. They looked wrong. I knew it as soon as I saw them.
- I think we should sleep outside tonight.
- What else do you do besides drinking?
- One time I thought wine was a man's best friend.
- And now?
- Well. now I realize, a good woman is much better. A woman like you.
- Hey, listen, it seems to me this damn job will kill us. I feel it.
- You are right. Up till now we have lost eight men and that gang is good. Too good.
[...]