Orbit

Nitrogen Man Dive Calculator – Description & User Guide

What It Does

The Nitrogen Man calculator is an interactive dive planning tool designed to help divers visually and numerically track their nitrogen loading, no-decompression limits (NDL), and overall dive safety margins.

It adapts U.S. Navy-style NDLs but makes them 5% more conservative, producing Maximum Dive Limits (MDL) that account for a safety buffer beyond the base Navy values.

The calculator is especially useful for:

• Single dive planning – Find your MDL for a given depth before exceeding no-decompression limits.
• Repetitive dives – Track residual nitrogen between dives and see how surface intervals affect your limits.
• Risk assessment – Monitor nitrogen loading percentage (NI%), oxygen partial pressure (ppO₂), and safety stop requirements.
• Visual awareness – A “Nitrogen Man” graphic fills or empties to show real-time loading/unloading of nitrogen.

How to Use It

1. Set Dive Depth
   • Enter the planned depth (in meters) in the “Depth” column for each dive row.
2. Enter Dive Time
   • For a planned dive, enter your Planned Bottom Time (PBT) in minutes.
   • You can also import from a previous plan using “Use Plan.”
3. Surface Interval (SI)
   • Between dives, enter your surface interval time in minutes. The calculator will automatically adjust your residual nitrogen time (RNT).
4. Review Key Outputs
   • RNT: Residual Nitrogen Time carried over from previous dives.
   • TBT: Total Bottom Time (RNT + Actual Bottom Time).
   • NDL / MDL: Remaining no-decompression limit at the planned depth.
   • ppO₂: Oxygen partial pressure for the dive (based on entered FO₂).
   • NI%: Nitrogen Index – percentage of theoretical nitrogen capacity used.
   • Stop: Minimum safety stop time recommended.
5. Watch the Nitrogen Man
   • The diver graphic fills with nitrogen during dives and clears during surface intervals, providing a quick visual indicator of your current nitrogen load.
6. Risk Assessment Panel
   • Provides an overall “Low,” “Moderate,” or “High” risk rating based on nitrogen levels, oxygen exposure, and environmental conditions (wind, seas, tides, etc. if entered).

Tips for Best Use

• Always round up depth and time to the next higher value for added safety.
• Include a minimum 3-minute safety stop at 5 m (15 ft) for any dive approaching MDL.
• Remember that this calculator is for planning only—always dive within the limits of your certification, training, and conditions.
• Cross-check results with your dive computer and follow the more conservative of the two.