How can I keep my indoor cat from going outdoors?

[Brittany]

Recently I got a cat from a friend who could no longer keep him. He has a history of escaping the house and then returning the next morning. I have only had him for a few days and havnt experienced this yet but am worried that I will. Hes completely declawed and fixed. I also have two other cats he is not fond of yet. Im afraid that if he gets out, he wont come back here because he has only been here a few days and doesnt like the other cats. I was thinking of getting him chipped or buying a breakaway collar with a tag on it. But if nobody turned him into a shelter or vet, they wouldnt discover the chip. And if the breakaway collar broke away before hand, they wouldnt know to call me. I really dont want to have to put a collar on him. I was thinking about getting a boundarys spray and spraying it infront of all the doors. I also have a dog though and dont want her to be effected by it since she has to pass the door to come outside and go potty (not dog door, i take her out). Is there a spray that I can get that only effects cats? And that I dont have tl contiously spray in order for it to work? Is there something else someone could recommend? I want him to be 100% indoors like my other two cats. Thanks in advanced for the help.
I cannot lock him in a room every time the door gets opened.

1. Everytime? Come on.. Someone knocks on the door and im suppose to hunt for this cat around the house, catch him if hes caught onto the 'you get locked up when the door opens' thing, ect ect..

2. Im not the only one living with this cat. There are 5 people all together in the house who could open the door at anytine :/

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We are trying to keep an eye on the sneaky little guy when we open a door. I really just want to know if theres an easier way to keep him in

[Gilb]

I know exactly how you feel, my own cat is a door dasher and it's next to impossible to keep her inside. Make sure that your doors are not easily pried/pushed open, something like a screen door is very easy for a cat to open. Any doors like that should be locked/blocked/jammed so that only a human can open it. Make sure everyone in tho house understands that the cat may dash at the door, and post warnings on all your doors. This should help prevent your cat from escaping. If your cat does escape, hopefully he will be picked up by a shelter or somebody who will make the effort to find the owner. Most people who find a declawed cat are smart enough to know that somebody owns that pet.

[ladystang]

put in crate before any door is opened.
shut in another room before door is opened.