When To Equalize
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.
The good news: as you go deeper, you’ll have to equalize less often—another result of Boyle’s Law. For example, a descent of six feet from the surface will compress your middle ear space by 20 percent and produce pain. But from 30 feet you’d have to descend another 12.5 feet to get the same 20 percent compression.
When you reach your maximum depth, equalize again. Though the negative pressure in your middle ear may be so small that you don’t feel it, if it’s maintained over several minutes it can gradually cause barotrauma.