What the ?! How is being deprived of oxygen, and choking yourself to death by breathing, be considered humane? It can take up to 45 minutes for death to come by CMP. I doubt a shelter would go above 16% and endanger themselves.The process involves convulsing, nervous system shutting down, vomiting, and dizziness, that is what they feel while slowly being suffocated to death, and not even knowing what is happening to them. Research mode!