Yes some full face snorkel masks are dangerous due to CO2 build up inside the mask. In this video we tell you how to pick a safe mask and to check if your own full face mask is dangerous.
Safe full face snorkel masks:
Tribord EasyBreath on Amazon: http://geni.us/6j1k
Ocean Reef Aria on Amazon: http://geni.us/LIw1S
H2o Ninja on Amazon: http://geni.us/I9mT
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