@@IslandHopperTV Exhaled air contains more CO2 than the air we inhale. If we do this in a closed space, like a full face snorkel mask, we won't exhale deeply enough to push all the bad air out. It's like breathing in a closed bag where the CO2 keeps on building until it becomes very toxic. They are actually banned in Hawaii.
@@IslandHopperTV The primary and overriding concern with full face masks is CO2 build up in the mask. Humans exhale carbon dioxide (CO2) when they breathe, and this CO2 can collect in the voids inside the mask when being used in the water. When CO2 levels increase in the mask, users may experience headaches, panic, dizziness, and unconsciousness.
