The bubbler is the safety. 4 liters a minute is ALLOT. how big is your generator?
You sure its not 4 liters per hour? Also you have to have a balance between output and longevity. Some of the bigger cells make more HHO, but they tend to boil the water and just steam after a short period. You probably did the cheaper mason jar one. they work, but they don't produce 4 liters a minute. more like 2 per hour. And they dont last as long. And they boil the water. 4 liters a minute can be heard like a hiss. We only admin 3 liters per minute or so for o2 patients via Nasal cannula (the nose one). I built this one with hi grade durable stuff. With safety, and longevity in mind. Hence the higher cost.