I read somewhere that flea collars can be used in vacuum cleaner bag to kill alive fleas. When you vacuum cat or dog area there might be some fleas and their larvas around which you will get into vacuum cleaner bag.

The thing is they won’t die so easily and there is nothing that can’t prevent them to jump out of bag. You could throw away bag with fleas, but cleaner bags are not so cheap.

Tip about flea collars I heard is to put used flea collar in the vacuum cleaner bag to kill all the alive fleas and prevent them to get out of it. You could even use new flea collar cut in smaller pieces.