Surface Interval Rules
Before we begin using Table 2, let's look at some rules to follow that increase your safety.
Surface intervals must be at least 10 minutes long
It's common for divers to surface during a dive for a brief moment. If the time you spend at the surface is less than 10 minutes, your dive time continues when you descend.
A surface interval of 1 hour or longer is recommended
A significant amount of nitrogen is offgassed during the first hour of your surface interval. In many cases, your letter group will not even change after less than one hour.
All residual nitrogen is considered offgassed 24 hours after your last dive
No matter what your end-of-dive letter group is following a dive, it takes 24 hours to completely offgas all residual nitrogen.
