Equalisation            (Page 1of 2)

Atmospheric pressure
During our whole life we are under pressure. This pressure is caused by the weight of air pushing down on us and is called the atmospheric pressure. During descents in diving, the pressure on your body increases. This is because more water is pushing down on you, creating more and more water pressure on the body.

Air spaces
In our body are air spaces that you can equalize, either manually or automatically. The most obvious air space that equalizes automatically are the lungs, equalization occurs with every breath. An air space that doesn't equalize automatically is the middle ear. The middle ear is enclosed by the ear drum and the Eustachian tube. The ear drum is able to flex inward and outward, allowing for small pressure changes.

The Eustachian tube
The Eustachian tube is a tube that links the pharynx to the middle ear and is normally closed but can be opened to let a small amount of air through to equalize the middle ear.

When do you equalize?
Equalizing should be done before pain or discomfort occurs. During diving, equalizing should be performed every few feet during descend. If it is too painful to equalize, then prevent further increase of pressure and try again later. Never force to equalize, this can cause the round window to rupture.

Why exactly do you have to equalize?
From According to Boyle's Law, as the pressure increases on descent, the volume of a gas in an enclosed space decreases proportionately. As the pressure decreases on ascent, the volume of the gas increases proportionately. If you need more info on this then I would suggest a search for Boyle's law and equalizing.

Tips for equalizing during SCUBA diving
Before your descent, inflate your ears gently with one of the techniques described below to create a little extra air in the middle ear and sinuses.