Pressure equalization occurs when fluid in a reservoir flows from a zone at high pressure to the zone at low pressure. This communication happens between two production zones with different pressure characteristics.

How long does it take to equalize pressure?

Sooner, and more often, than you might think. Most authorities recommend equalizing every two feet of descent. At a fairly slow descent rate of 60 feet per minute, that's an equalization every two seconds. Many divers descend much faster and should be equalizing constantly.

Why does pressure try to equalize?

Oxygen is constantly absorbed by the tissues of your middle ear, lowering the air pressure in those spaces. When you swallow, your soft palate muscles pull your Eustachian tubes open, allowing air to rush from your throat to your middle ears and equalize the pressure.