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Vincent Perrin edited this page Jan 19, 2026 · 1 revision

❓ Frequently Asked Questions

Common questions and answers about the Decompression Calculator.

Table of Contents

  1. General Questions
  2. Usage Questions
  3. Technical Questions
  4. Algorithm Questions
  5. Safety Questions
  6. Troubleshooting

General Questions

What is the Decompression Calculator?

The Decompression Calculator is an educational web application that calculates decompression dive profiles using the Bühlmann ZHL-16C algorithm with gradient factors. It helps users understand decompression theory and dive planning.

Is this application safe to use for real dive planning?

No. This application is for educational purposes only. Never use it to plan real dives. Always use:

  • Certified dive computers
  • Proper dive planning procedures
  • Professional dive planning software
  • Guidance from certified instructors

Is the calculator free to use?

Yes, the calculator is completely free and open-source.

What browsers are supported?

The calculator supports:

  • ✅ Chrome/Edge (latest 2 versions)
  • ✅ Firefox (latest 2 versions)
  • ✅ Safari (latest 2 versions)
  • ✅ Mobile browsers (iOS Safari, Chrome Mobile)

Can I use this offline?

Currently, the calculator requires an internet connection. Offline support is planned for future releases.

Is my data stored on servers?

Diver information is optionally stored on the server with encryption. All dive calculations are performed client-side in your browser. You can delete your data at any time.

Usage Questions

How do I calculate a simple dive?

  1. Navigate to the Calculator page
  2. Enter depth (meters)
  3. Enter bottom time (minutes)
  4. Select gas mix (Air, Nitrox, etc.)
  5. Adjust gradient factors if desired
  6. Click "Calculate"

See the User Guide for detailed instructions.

What are gradient factors?

Gradient Factors (GF) are percentages that modify the Bühlmann algorithm to make it more or less conservative:

  • GF Low: Applied at first decompression stop (e.g., 30%)
  • GF High: Applied at surface (e.g., 70%)

Lower values = more conservative = longer decompression time.

See Algorithm Details for more information.

How do I plan a multi-level dive?

  1. Switch to "Advanced Mode"
  2. Click "Add Segment" for each depth level
  3. Enter depth and duration for each segment
  4. Select gas mixes
  5. Calculate

See User Guide - Multi-Level Dives.

What gas mixes are supported?

  • Air (21% O₂)
  • Nitrox (EAN32, EAN36, custom)
  • Trimix (custom O₂/He/N₂ ratios)
  • Oxygen (100% O₂ for deco)

How do I change the language?

Click the language switcher in the top-right corner to toggle between English and French.

Can I export my dive plan?

Yes! Click the "Export PDF" button to generate a printable dive plan including:

  • Dive parameters
  • Profile chart
  • Decompression schedule
  • Safety warnings

How do I save diver information?

  1. Click "Diver Info" in the navigation
  2. Enter your information
  3. Click "Save"

Your information is encrypted and stored locally or on the server (depending on configuration).

Technical Questions

What algorithm does the calculator use?

The calculator uses the Bühlmann ZHL-16C algorithm with gradient factors. This is the same algorithm used in many modern dive computers.

How accurate are the calculations?

The calculations are mathematically accurate implementations of the Bühlmann ZHL-16C algorithm. However:

  • Individual physiology varies
  • Environmental factors matter
  • This is for education only
  • Always use certified equipment for real dives

What are the tissue compartments?

The Bühlmann algorithm models 16 theoretical tissue compartments with different nitrogen half-times ranging from 4 minutes (fast tissues) to 635 minutes (slow tissues).

Can I compare different decompression models?

Yes! Navigate to "Decompression Models" to compare:

  • Bühlmann ZHL-16C
  • RGBM (Reduced Gradient Bubble Model)
  • VPM-B (Varying Permeability Model)
  • US Navy Tables

Does it support repetitive dives?

Yes! The "Repetitive Dives" feature allows you to:

  • Plan multiple dives
  • Calculate surface intervals
  • Track tissue desaturation
  • Account for residual nitrogen

What is the maximum depth supported?

The calculator supports depths up to 100 meters. However, recreational diving limits are typically 40 meters, and technical diving requires specialized training.

Can I use imperial units?

Currently, the calculator uses metric units (meters, minutes). Imperial unit support is planned for future releases.

Algorithm Questions

What is the Bühlmann ZHL-16C algorithm?

The Bühlmann ZHL-16C is a decompression algorithm developed by Dr. Albert Bühlmann. It models inert gas absorption and elimination in 16 tissue compartments to calculate safe ascent profiles.

What are M-values?

M-values (Maximum values) represent the maximum inert gas pressure a tissue compartment can tolerate at a given ambient pressure before decompression sickness risk becomes unacceptable.

How do gradient factors modify M-values?

Gradient factors reduce M-values to create more conservative profiles:

Adjusted M-value = M-value × Gradient Factor

For example, with GF 70%, the adjusted M-value is 70% of the original.

What is the Schreiner equation?

The Schreiner equation calculates tissue loading at constant depth:

P_tissue = P_inspired + (P_initial - P_inspired) × e^(-k×t)

Where:

  • k = ln(2) / half-time
  • t = time at depth

What is the Haldane equation?

The Haldane equation calculates tissue loading during depth changes:

P_tissue = P_i0 + R × (t - 1/k) - (P_i0 - P_initial - R/k) × e^(-k×t)

Where R is the rate of pressure change.

How is the decompression ceiling calculated?

The ceiling is the shallowest depth where tissue pressure equals the adjusted M-value. Ascending above the ceiling increases DCS risk.

What is NDL (No-Decompression Limit)?

NDL is the maximum time you can spend at a depth without requiring decompression stops. It's calculated by determining when the fastest tissue reaches its M-value limit.

Safety Questions

Why shouldn't I use this for real dives?

This calculator is educational and:

  • Not certified by diving organizations
  • Doesn't account for individual physiology
  • Doesn't consider environmental factors
  • Lacks real-time monitoring
  • Has no liability or warranty

Always use certified dive computers and proper training.

What are the safety warnings?

The calculator provides warnings for:

  • High PPO₂: Oxygen toxicity risk
  • Low PPO₂: Hypoxia risk
  • High END: Nitrogen narcosis risk
  • Excessive Deco: Very long decompression time
  • MOD Exceeded: Depth exceeds gas maximum operating depth

What is oxygen toxicity?

Oxygen becomes toxic at high partial pressures:

  • Working limit: 1.4 bar PPO₂
  • Decompression limit: 1.6 bar PPO₂
  • Symptoms: Convulsions, vision problems, nausea

The calculator warns when PPO₂ exceeds safe limits.

What is nitrogen narcosis?

Nitrogen has narcotic effects at depth, similar to alcohol intoxication. The calculator calculates Equivalent Narcotic Depth (END) and warns when it exceeds 30 meters.

What is decompression sickness (DCS)?

DCS occurs when dissolved gases form bubbles during ascent. Symptoms include:

  • Joint pain ("the bends")
  • Neurological symptoms
  • Breathing difficulties
  • Skin rashes

Proper decompression procedures reduce DCS risk.

What should I do if I get DCS?

This is a medical emergency:

  1. Call emergency services immediately
  2. Administer 100% oxygen if available
  3. Keep the diver lying down
  4. Do not attempt recompression without medical supervision
  5. Transport to hyperbaric chamber

Emergency Numbers:

  • DAN (Divers Alert Network): +1-919-684-9111
  • Local emergency: 911 (US) / 112 (EU)

Troubleshooting

The calculator won't load

Try these steps:

  1. Refresh the page (Ctrl+F5 or Cmd+Shift+R)
  2. Clear browser cache
  3. Try a different browser
  4. Check your internet connection
  5. Disable browser extensions

Calculations seem incorrect

Verify:

  1. Input parameters are correct
  2. Units are as expected (meters, minutes)
  3. Gas mix percentages sum to 100%
  4. Gradient factors are reasonable (30/70 is standard)

If issues persist, report a bug.

The chart doesn't display

Solutions:

  1. Ensure JavaScript is enabled
  2. Update your browser
  3. Try a different browser
  4. Check browser console for errors (F12)

I can't save diver information

Check:

  1. Browser allows local storage
  2. Not in private/incognito mode
  3. Sufficient storage space
  4. Backend API is accessible (if using server storage)

Export PDF doesn't work

Try:

  1. Allow pop-ups for the site
  2. Update your browser
  3. Try a different browser
  4. Check browser console for errors

Language switching doesn't work

Solutions:

  1. Refresh the page
  2. Clear browser cache
  3. Check that JavaScript is enabled

Mobile app doesn't work properly

Tips:

  1. Use landscape orientation for better layout
  2. Ensure stable internet connection
  3. Update your mobile browser
  4. Try desktop version if issues persist

API requests fail

Check:

  1. Internet connection is stable
  2. Backend server is running
  3. CORS is properly configured
  4. Rate limits not exceeded
  5. Check browser console for errors

Feature Requests

Can you add feature X?

We welcome feature requests! Please:

  1. Check existing issues first
  2. Open a new issue with detailed description
  3. Explain the use case
  4. Be patient - we're a small team

When will feature Y be available?

Check the project roadmap for planned features and timelines.

Can I contribute?

Yes! See the Contributing Guide for how to get involved.

Getting Help

Where can I get more help?

How do I report a bug?

  1. Check if it's already reported
  2. Open a new issue on GitHub
  3. Include:
    • Steps to reproduce
    • Expected behavior
    • Actual behavior
    • Browser and version
    • Screenshots if applicable

How do I request a feature?

  1. Check existing feature requests
  2. Open a new issue with "Feature Request" label
  3. Describe the feature and use case
  4. Explain why it would be valuable

Is there a community forum?

Yes! Join discussions on GitHub Discussions to:

  • Ask questions
  • Share dive plans
  • Discuss features
  • Help other users

Educational Resources

Where can I learn more about decompression theory?

Recommended Resources:

What diving certifications do I need?

For recreational diving:

  • Open Water Diver (basic)
  • Advanced Open Water (deeper dives)
  • Nitrox certification (for enriched air)

For technical diving:

  • Technical Diver certification
  • Trimix certification (for helium mixes)
  • Decompression Procedures course

Are there any books you recommend?

  • "Deco for Divers" by Mark Powell
  • "The Physiology and Medicine of Diving" by Bennett and Elliott
  • "Technical Diving in Depth" by Bruce Partridge
  • Bühlmann's original works (advanced)

About the Project

Who created this calculator?

This is an open-source project created for educational purposes. See the GitHub repository for contributors.

Is the source code available?

Yes! The project is open-source and available on GitHub.

How can I support the project?

  • ⭐ Star the repository
  • 🐛 Report bugs
  • 💡 Suggest features
  • 🔧 Contribute code
  • 📖 Improve documentation
  • 💬 Help other users

What license is it under?

See the LICENSE file in the repository.

Still Have Questions?

If your question isn't answered here:

  1. Check the User Guide
  2. Search GitHub Issues
  3. Ask in GitHub Discussions
  4. Open a new issue

Next: Troubleshooting - Detailed problem-solving guide

Previous: Security Best Practices - Security guidelines

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