Ok, so what is a 'kill' shelter? This is a shelter that will take xx amount of animals and put them to sleep, no matter what. This dog/cat/skunk/guinea pig/horse has been here three months? Send them across the rainbow bridge. No one wants them.
Just on sort of a side note...my father in law keeps telling me (and telling me and telling me and TELLING ME) about the time he, supposedly, worked in a shelter. Supposedly, he would kill the dogs as soon as they came in. No matter what. According to him, he was always being appreciated due to his 'clean kennels' Do I believe him? Not really. Even way back then, they would NOT have allowed that. Do I listen? Well, he is 90 years old. I do have respect for my elders. I won't say anything back to him about it.
Ok, so what is a 'no kill' shelter? We are the Humane Society. Our job and primary mission is to take in, vet and adopt out healthy animals. We cannot adopt out ferals, sick animals or kittens that are too young. In fact, many states now say you MUST have all animals spayed or neutered before adopting.
We do NOT kill for space. However, each animal is tested. Puppy has parvo? To prevent it from dying a horrid death, our Vet will put them to sleep. Cat or kitten has felv or fip? A 'mercy' shot to, again, prevent a horrid death. Cat or dog is feral, or too aggressive for handling? Yep, bring out the mercy shot. We really have no facilities for dealing with feral or highly aggressive animals without harm to us.
Other things, yet our Vet will do an 'abort/spay' if the female animal is pregnant. To her, and in fact, to most of us, it is very much approved over the idea of baby animals being born in a cage. While we do have litters either born there, or brought in, we prefer to have those fostered out, until old enough to adopt. We also have our kitten room, where I can put in 12 kittens, so they have the freedom to socialize, play, groom each other (hear me guys and gals?) and generally, well...be kittens.
I also get the fun task of 'gentling' feral kittens. I feel, strongly, that any kitten four months old or younger can be tamed. So far, I've not been proved wrong. Anything older, I would be cautious with. After all...a three pound, or smaller kitten who is hissing and spitting is cute. Anything bigger, approach with caution, or you might be bleeding. In fact, make that WILL be bleeding.
We are a no kill shelter. Sadly, that does mean we are full. Most of the time. Because people keep BRINGING us animals.