Deep air diving to 55 m
TDI Extended Range is a course for experienced divers who have completed TDI Advanced Nitrox and Decompression Procedures. You learn to dive safely on air to 55 metres when staged decompression is required, using nitrox mixes and oxygen for decompression. The course teaches the right techniques, the equipment requirements and the hazards of deep air diving.
After the course you can continue with TDI Advanced Wreck and trimix training.
What you learn
- Theory: the history of deep air diving, pressure and planning formulas: maximum operating depth (MOD), best mix.
- Physiology: hypoxia, oxygen toxicity, nitrogen narcosis, carbon dioxide and carbon monoxide hazards, overheating and hypothermia.
- Decompression: planning with air, nitrox and oxygen, decompression models (Bühlmann, DCIEM, US Navy) and computer-generated tables.
- Planning: organising the dive and the team, gas requirements, oxygen and nitrogen limits, contingency plans.
- Procedures: descent and ascent, recognising narcosis, breathing at depth, navigation from shore or from a descent line.
Practice in the water
You make four open-water dives with at least 100 minutes in total: all deeper than 30 m, two of them deeper than 40 m. You work with two stage cylinders: two decompression gases, or one decompression gas and extra bottom gas.
In the water you practise the skills a deep dive calls for: confirming gas switches with your buddy, deploying a lift bag from depth, an air-sharing ascent with one diver without a mask, isolating a failed regulator, and towing an unconscious diver to the ascent line. After a simulated loss of decompression gas you work out a contingency decompression plan. The course ends with a written exam.
Frequently asked questions
Why do I need so many dives before the course?
TDI requires at least 100 logged dives, 25 of them deeper than 30 m, because every course dive goes deeper than 30 m. Experience at depth lets you focus on the procedures.
Can I dive deeper than 55 m?
Not on air. Deeper dives use trimix, which needs separate trimix training.
How long does the course take?
4–5 days: theory (TDI sets at least 8 hours), the exam and four deep dives.
What equipment do you provide?
Air and nitrox cylinders, regulator sets with backup regulators and safety equipment. We go through the exact list before the course.