16 Mar

IDC Internship Note – Residual Nitrogen Time (RNT)

Diving has to be one of the most exciting outdoor activities.  To get the best out of a diving experience, it is advisable to undertake proper training from a scuba instructor. In fact, this is part of any training for divemaster certification.

While you might have a knack for natural diving, there is always the technical aspect that comes with it. One of the most important skills you will learn is of course diving tables. The two-sided table is confusing for a beginner yet understanding them not only enhances your diving experience but also boosts your safety while underwater.

One of the critical numbers on a dive table is residual nitrogen time. If you are having trouble getting the gist of residual nitrogen time, the following highlighted aspects will give you a better understanding. Take a look:

Calculating Nitrogen Absorption

Residual nitrogen time tracks nitrogen absorption over a number of dives as opposed to a single dive. You will not have a big problem calculating nitrogen absorption for one dive but for multiple dives, this can be tricky.

PADI Dive Table

Surprisingly, this just requires the use of the back side of a diving table and some calculations. However, you need to understand the idea behind the calculations to get this right. For starters, you need to understand that when underwater, a diver’s tissues absorb nitrogen from the environment or breathing gas.

No-decompression limit (NDLs) is the maximum amount of time a diver can stay at a given depth. These limits are used to prevent the diver from absorbing too much nitrogen which would lead to decompression illness. The deeper a dive is the higher the absorption of nitrogen and the faster a diver approaches NDL.

For residual nitrogen time calculation purposes, consider that nitrogen absorption can be understood to be proportional to depth. With this in mind, nitrogen absorption after a repetitive dive should be the sum of residual nitrogen time and actual dive time. The total and maximum dive depth are used to calculate nitrogen absorption.

Calculating Residual Nitrogen Time

Check the PADI dive table first to identify your pressure group. After this, follow these steps to calculate absorption of nitrogen on multiple dives:

  1. The diver’s pressure group after the surface interval should intersect with the box listing the highest depth of his dive.
  2. Check residual nitrogen time on the box at the intersection.
  3. When 2 numbers are provided, use the use the legend on the diving table to find the correct residual nitrogen time.

Refresh your dive table knowledge and make sure that you are always safe underwater. Should you be interested with this course, visit our page and take the Instructor Development  Course with IDC Internships Bali.

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