Thats horrifying, and it motivated me to do a bit of reading - most of what I saw suggested it was only used for containment of wide spread infections in factory farmed animal population (mad cow was the one that came up the most) and in those cases I can kinda understand the need to contain the animals and dispatch them....but the idea that it could last 3+ hours is still unacceptable.

I don't mind the killing, but it should be quick, efficient, and as painless as possible for the animal involved.