Unless you devise a way to let the CO2 out slowly, it is not going to benefit you much. Letting it all out at once is just going to give your ladies a quick breath, and then it will blow away and stabilize. If you are very committed to it, you could go in every day, shut off ventilation as well as possible, let a spurt of CO2 out of the extinguisher, and try to keep it in for an hour or so. However, It seems like it would be a big pain in the ass, and it isn't terribly cheap to get those things refilled anyway, and you will likely have to do it often.

S-Town