Equalization

The act of balancing pressure in the ears, sinuses, and mask against rising water pressure during descent, usually by gently pushing air into them.

Equalization means matching the pressure inside your air spaces, mainly the middle ears, sinuses, and mask, to the ambient pressure of the water around you. As you descend, water pressure rises quickly, about one atmosphere every 10 m or 33 ft, and the air trapped in those spaces compresses. If you do nothing you feel discomfort within the first few meters, and continuing down can cause real injury, so divers equalize early and often from the moment they leave the surface.

The most common technique is the Valsalva maneuver: pinch your nose and exhale gently against it, which pushes air up the Eustachian tubes into the middle ear. The Frenzel maneuver does the same job using the tongue instead of the lungs and is gentler on the ears. Add a puff of air through your nose into the mask to prevent mask squeeze. The golden rules are equalize before you feel pain, never force it, and if an ear will not clear, ascend a meter and try again.

Congestion from a cold or allergies blocks the Eustachian tubes and makes equalization difficult or impossible, which is why diving sick is a bad idea and can end in barotrauma or a reverse block on ascent. Descending feet first along a line, tilting the blocked ear upward, and swallowing or wiggling the jaw all help. If equalization problems keep recurring on your dives, it is worth noting in your dive log and mentioning to a dive physician.