In reply to johncook:
Although it's one recommended method of killing things like adult fleas and house dust mites on bedding/toys etc, I'm not completely certain you could 100% rely on it killing flea eggs or larvae - during a wildlife crime investigation I've had maggots come back to life after being on a carcass in a freezer for a week!
Best option (if you really need stuff to kill fleas on a sleeping bag) is to speak to your vet.
The fleas must have come from somewhere - they don't miraculously appear in a sleeping bag - so the chances are your dog or cat needs treatment and the veterinary products are far better than Over The Counter ones. Your vet will also have products suitable for treating furniture etc, which could be used on the sleeping bag (though I'd wash/rinse it thoroughly afterwards too).
In any case that's a safer option than clicking links in a web post by someone with dodgy English that's only registered 5 minutes before......
Post edited at 17:16