I know that I can limit the number of chats posted, but how

I know that I can limit the number of chats posted, but how do I make them disappear after (for example) 12 hours. My chatters are coming into chat and seeing the conversations that were there from yesterday. They should be long gone.

I know that the rooms can be cleared manually. This is not a good solution. I need them to be automatically removed after a certain period of time has elapsed.

Thank you.