Humane Euthanasia?

A recent news story touched my animal loving nerve.  Recently an unnamed, unwanted Beagle mix dog was dropped off at an Alabama pound.  Sadly this dog's fate was to enter the gas chamber, a carbon monoxide filled stainless-steel box with a group of other unwanted, unloved animals.  Shockingly, when the "chamber" was opened after the dogs were "put to sleep" permanently, this little dog walked out and has since been named "Daniel".  In looking into this, I found that only three animals have survived this experience at this particular Alabama facility in the last 12 years.  Though I am overjoyed that three animals survived this horrible fate, what I want to know is how humane is this form of ending an unwanted animal's life if they can actually survive?  How brutal must the experience be for the animal to struggle through this horror?  I truly understand the plight of animal over-population but cannot fathom why, if an animal's life must be ended for whatever reason, it is not done quickly and quietly with the least amount of stress.  Surely we as a "humane" society owe this much to a defenseless animal!  Daniel has since been flown to New Jersey and is being fostered until a permanent home is found for him.  Why does it take a story like this to make people wake up and offer to foster and adopt unwanted animals?  How many more animals have survived similar circumstances, not made the newspapers, only to relive the experience with a permanent outcome?

MASON The MIRACLE DOG

Every now and then, something happens to make me believe that maybe there really are miracles.

Mason, a terrier mix, was hiding in his owners' garage in Alabama, when he was sucked up by the tornado raging through his city.

When his owners returned to their damaged home three weeks later to sift through the debris, they had almost given up hope of ever seeing their pet again.

To their surprise, they found Mason waiting for them on the porch. His two front legs were fractured so he had had to crawl on two broken legs to get home.
With the care of a generous vet, Mason is on the mend. 
Wishing the best to Mason, his family and all the other victims of the horrific tornadoes.