Here are some key points on pressure changes.
- As pressure increases, volume decreases and vice versa. This is why you add gas to your BCD, mask, and ears as you descend and why you let gas out of the BCD when you ascend.
- As pressure increases, gas density increases. This is why you breathe more at depth and you need to inhale more gas to fill your lungs as you descend.
- Remember, at depth, the gas density increases, and you will consume more gas. Monitor your instruments frequently. You will have longer dive times the shallower you are.