PADI Divemaster Certification Practice Exam

How does increasing depth affect the density of air breathed from a cylinder?

1. It becomes less dense

2. It stays the same density

3. It becomes denser

4. It becomes highly combustible

The correct answer is: It becomes denser

As a diver descends into deeper water, the pressure exerted on them increases. This increase in pressure causes the air in the cylinder to become denser. This phenomenon occurs because compressing gas in a given volume results in an increase in density, as per the principles of gas behavior. When you inhale air from a cylinder at greater depths, the molecules of gas are packed closer together due to the combined effects of water pressure and the cylinder's pressure. This leads to a higher number of air molecules per unit volume, resulting in denser breathing gas. This increase in density can have implications for divers, such as the need to manage the potential for nitrogen narcosis and other physiological effects associated with inhaling higher pressures of gas. The options suggesting that air becomes less dense or stays the same density do not accurately reflect the impact of depth on gas behavior, while the notion of increased combustibility is unrelated to the principles governing gas density at depth.