IANTD Open Water Diver Practice Exam

Blowing through your nose to equalize is the correct technique to prevent a mask squeeze while diving. This technique works because as a diver descends, the pressure around them increases, which can cause a difference between the pressure inside the mask and the surrounding water pressure. A mask squeeze occurs when the pressure inside the mask is lower than the external pressure, leading to discomfort or potential injury.

By blowing gently through your nose while pinching it shut, you increase the air pressure inside the mask to match the surrounding water pressure. This equalization helps maintain comfort and prevents the mask from being sucked tightly against your face, thereby mitigating the risk of a mask squeeze.

Using a larger mask size may not adequately address the underlying cause of pressure differences, as the pressure can still become unbalanced regardless of the mask size. Clearing the mask with water can serve to remove water that gets inside the mask but will not prevent the pressure differences that lead to a squeeze. Reducing the air pressure in the mask is actually contrary to what is needed, as it would exacerbate the issue instead of alleviating it.