gas masks are designed to allow you to breathe in through the filter and out through the exhaust vents, which are designed to open only with exhale pressure. make sure they are functioning properly, that's your most likely problem, you have to have the bowl piece attached to the (most likely) side part on the jaw where the filter normally screws. I would suggest using a hollowed out filter (you can get 'em at army surplus store) If you still blow out through the bong, then you need to replace the exhaust seals (Part Numbers should be on them, and can be ordered on the internet.)