PADI Divemaster Certification Practice Exam

If a compartment has reached half saturation after 60 minutes, how far along is it towards equilibrium after another 120 minutes?

1. 25%

2. 75%

3. 100%

4. 50%

The correct answer is: 75%

When considering the factors related to compartment saturation during decompression, it's important to understand how the body absorbs and eliminates nitrogen during the ascent or dive. After a compartment has reached half saturation, which typically indicates a well-established absorption curve, continued saturation towards equilibrium does not follow a linear progression but rather an asymptotic approach. This means that as a compartment approaches full saturation, the rate of saturation decreases over time. In this scenario, if the compartment is at 50% saturation after 60 minutes, further time will lead it to continue saturating, moving towards the 100% saturation point. While it may seem logical to assume that another 60 minutes would allow the compartment to reach full saturation at the same absorption rate, the reality is that the rate slows down considerably as the compartment approaches its saturation limit. Typically, after an additional 120 minutes (which is double the time already accounted for), the compartment is estimated to be around 75% saturated. This value reflects the characteristic non-linear absorption of nitrogen; thus, it indicates that the compartment is progressing steadily towards equilibrium but has not reached it completely. So, the consideration of compartment behavior and saturation curves confirms that the compartment is approximately 75% along its way to full saturation after