A more humane chicken culling method?

I know all the other methods; broomstick, sharp knife, etc.

Has anyone rigged up a nitrogen gas "chamber" to send their chickens off? My flock has Marek's, and I really don't like having to be hands on when it comes time for them to pass. I was thinking of rigging up one of the large Rubbermaid storage bins with a small line connected to a nitrogen cylinder. Set the chicken inside with some treats, mealworms, maybe a cell phone playing YouTube(they seem to enjoy it), and then open the valve. I would clearly do this outside (I live rurally), have a cover on the bin, and be standing upwind from the bin. I realise this sounds expensive and ridiculously over the top, but they're more my pets than livestock. Any thoughts or advice?