It's another way of supplying oxygen without having to wear air tanks, mask, and gear. The Oxygen Bubble Distributor and the Oxygen Sealer both supply oxygen, but the sealer makes it only fill rooms. The bubble distributor just creates a bubble of air. In a way, it's just to make things look better. I also like them because they add a more realistic feel to the game for me. I think each sealer can also supply a larger area with oxygen than each bubble distributor.