Why TEC 40?

I’m a diver who would like to dive to 40m, why should I complete the TEC 40 course when I already have the completed the Deep Speciality?

To complete the TEC 40 course in addition to being a deep qualified diver you will need to have completed 10 dives deeper than 30 metres. Be qualified to dive with enriched air and have dived at least tem times on enriched air below 18 metres. You will also need to be a PADI advanced open water diver. You will, because of these pre requirements be a more experienced diver than when you completed your deep course when you start your TEC 40.

Whilst studying for the TEC 40 you will learn how to use dive decompression software, to plan your dives, which will include, decompression dives with no more than 10 minutes total decompression time. You will learn how to use a single decompression gas with up to 50% oxygen. This gas will add conservatism to your decompression profile. You will start to use technical scuba equipment, twin cylinders joined by a manifold or side mount cylinders, each with its own independent regulator.

So the training is for divers who

  1. Want to extend their learning
  2. Want to learn to dive with technical equipment
  3. Want to use up to 50% enriched air
  4. Want to dive beyond recreational limits

There are five goals in the TEC 40 course

  1. To qualify you to make gas switch, extended no decompression dives, decompression stop dives, using enriched air and oxygen to 40 meters, using technical diving equipment and procedures required to manage the risks involved.
  2. To train you in the motor skills required for technical scuba diving.
  3. To assure you understand and acknowledge the hazards and risks involved with the above types of technical diving, as well as the limits to training received in the course.
  4. To train you to prepare for and to respond to reasonably foreseeable emergencies that may occur in this type of technical diving.
  5. To provide the foundational skills for further training in technical diving.

The TEC 40 course is technical diving but it is not about deep dives and long decompression hangs at this level. Technical diving is not for everyone. It is not necessary to be a TEC diver to enjoy diving, nor should you think of it as an inevitable step in a diver’s growth. You can enjoy diving for decades without ever making a technical dive. But, this step allows you to start to expand the recreational dive limits.

There are some new terms (lingo) to learn these include:

  • Algorithm, Particular version of a decompression model
  • Back gas, the gas in your doubles; usually the lowest oxygen blend you have, used on the deepest part of the dive.
  • Blow a bag Send up a lift bag.
  • Blow up Lose buoyancy control and ascend out of control, esp. in a dry suit.
  • Bust a stop Skip a required decompression stop, due to error or emergency.
  • Deco Short for “decompression;” as in “That calls for six deco stops,” “That was a short deco,” or “What deco tables are you using?”
  • Hang Decompression stop or stops, as in “How long was the hang?” Comes from hanging on to an anchor or mooring line while decompressing
  • Hyperoxic gas A gas blend with more than 21per- cent oxygen.
  • Hypoxic gas A gas blend with less than 21 per- cent oxygen
  • Jon line Short line used to clip you to the anchor line while decompressing in a current.
  • Kit long hose Your set up gear; scuba unit. The primary second stage on an approximately 2.2 meter hose that you breathe from, and pass to a team mate in an emergency
  • MOD Maximum Operating Depth —
the maximum acceptable depth
at which you can breathe a gas (based on oxygen partial pressure). With “operating” superfluous, many divers just use “Maximum Depth” interchangeably with “MOD.”
  • O2 (oh-two) software Computer software used for creating custom dive tables.
  • Stage To leave something to retrieve later, especially a stage bottle or decompression cylinder. Sometimes used as short for “stage bottle.”
  • Third Most common reserve in TEC diving — saving one third of gas for emergencies
  • Tox To suffer oxygen toxicity; often a reference to a CNS convulsion.
  • Turn pressure thepressure at which you end the dive, or turn toward the exit, so that you end with the required reserve.
  • Wings Tec diving BCD bladders; also brand name of a BCD.


The Good (TEC) Diver

The course is interesting and builds on the foundations you already have as a diver you learn to be a responsible TEC diver and demonstrate the characteristics every TEC diver should have:

Self-Sufficient. The responsible TEC diver plans and executes each dive as though it’ll be necessary to make the dive and handle all emergencies alone. That is, you should never rely on any other diver for the safety or knowledge required to execute a dive.

Team Player. Although self sufficient, the responsible TEC diver, dives as part of a team. When you TEC dive, you need to think of yourself as a team player contributing to a team effort.

Disciplined. Technical diving has too little leeway for cutting corners, bending rules, disregarding dive plans, omitting safety equipment or exceeding the limits of your training and equipment. Responsible TEC divers maintain their self-discipline.

Wary. One of the best ways to come back from every technical dive is to assume that everything can and will go wrong, and then have contingency plans for when it does. Responsible TEC divers are just a tad paranoid, and it serves them well.

Physically Fit. Responsible technical divers exercise regularly, eat properly, see their physician regularly and maintain the fitness level they need for the dives they make. You need to be fit for the dives you make; this includes having sufficient physical reserve for emergencies.

Accepts Responsibility. To be a responsible technical diver, you need to accept responsibility for your personal safety, while accepting and acknowledging the risks and demands TEC diving imposes.

The TEC 40 training course includes:

Equipment, You also learn about the equipment and how it works what to do when it goes wrong. You learn where to store your spares and how to access them.

Gas planning, equivalent air depths, maximum blend depths, partial pressures, maximum operating depths, gas consumption, gas supply and reserves and oxygen toxicity.

Team diving, how this differs from buddy diving.

Dealing with emergencies, gas sharing, shut downs, and S drills.

Once you have done this you can get in the water there are four dives as part of this course and they are about linking the new skills that you have learnt and practically applying them. Many of the skills will be familiar to you.


Training Dive One (you can complete this in confined water) You complete an entry
, buoyancy/weight check you decent and as you descend you complete a descent check. Whilst neutral buoyancy you hover for one minute.

You have to simulate a regulator free flow valve shutdown drill,  within 30 seconds and a manifold leak  isolator shutdown again within 30 seconds. In my training we practiced the shutdowns over and over again so as to develop the muscle memory needed to do this in a real life situation. At the end of the dive we rechecked our weight with near-empty cylinders.

With the exception of the shut downs everything here will be familiar to all divers.


Training Dive Two

Before the second dive you learn about using a stage/decompression cylinder. You lean how to rig these, how to set them up and how to prepare them for use. You do some additional theory on decompression stops, gas switching and extended no stop diving. Decompression software and they introduce a new mnemonic to learn “A Good Diver’s Main ObjectiveIs To Live.”

Good – G – Gas management

Diver’s – D – Decompression

Main – M – Mission

Objective – O – Oxygen

Is – I – Inert gas narcosis

To – T – Thermal exposure

Live – L – Logistics

You also learn how to NO TOX gas switch, you

  1. N – Note your name and the maximum depth on the cylinder labels (if picking up a staged cylinder, you may do this as you retrieve the cylinder).
  2. O – Observe the actual depth and compare it to the maximum depth on the label.
  3. T – Turn on the valve. Check the cylinder pressure.
  4. O – Orient the second stage by pulling it from
the retaining bands, and tracing the hose from
the first stage to the second so there’s no doubt
you have the right one. Unblock the mouthpiece
(if using a block), test purge the regulator and then switch to the new gas.
  5. X – eXamine your teammates — follow the hose from their mouths to the cylinders and confirm that they’re not deeper than the maximum depth labeled. If necessary, signal to confirm that you have switched (point to second stage in your mouth and then the cylinder you’re using.)

On this dive you are also required to at 15 minutes bottom time, write SPG reading on your slate. You also put on, remove and put back on your stage/deco cylinder. You also stage and retrieve stage/deco cylinder. Complete a NO TOX gas switch. You complete the part i found most difficult in a dry suit which is the gas shut down drill — close and reopens both regulator valves and isolator valve, switch your second stages to make sure you stay with the open valve, and you have to do this all within 60 seconds. Complete a surface air consumption swim. You also have to deploy lift bag.

As we were all completing these dives on twins or side mount setup meant that we had loads of time and this training dive lasted eighty minutes. This meant that we again completed the drill repeatedly to gain that important muscle memory and mastery. These skills need to become really practiced and smooth.

Training Dive Three builds more on the first two dives.

On this dive you have to on reaching the SPG pressure designated by your instructor record the bottom time and  depth on our slate. You need to complete a three minute hover. You have to stage, retrieve and replace stages without stopping. Complete the removal and replacement of  stage/deco cylinders with no mask. You also have to deal with out of air problems by completing a long hose gas share a swim.  Then the simulated deco part of the dive you have to complete a midwater (on line) NO TOX gas switches, and measure your surface air consumption for ten min in midwater “deco stop”.

Now it is really ramping up for dive four,  you get to put everything you have learnt together and demonstrated that you are able to plan the dive following the A Good Diver’s Main Objective Is To Live procedure, and perform predive checks following the Being Wary Reduces All Failures procedure.

For our dive I was in the Red Sea diving on the Salem Express Wreck. We put on and took of our cylinder at the surface. Completed a managed descent at a controlled speed. On our descent we completed bubble and decent checks. We donated and received air on a long hose. We staged our cylinders, collected them and clipped them back on. We then completed shut down drills, this time in 45 seconds. We put up a bag and on the line completed a NO TOX switch. The decent we completed had to simulated 
two decompression stops, one at 6 meters for five minutes and the next at 5 meters for 12 minutes, breathing from the deco cylinder, and recording required information for subsequent decompression SAC calculations. Throughout the dive we showed that we  were aware of  dive time, depth, and gas usage by writing this on a slate every 35 bar of back gas used. This dive was a seventy minute dive and we complete a series of stop to the surface simulating ten minutes of decompression.

Due to being in the Red Sea were then able to go on and repeat these long dives with gas switching and decompression stops.  On completing these dives if you feel as i did you will feel really accomplished, you will have completed at least four dives that will have challenged your skills and experiences. You will have added to your overall diving skills learning and mastering shut downs and improving you stop control. Your knowledge will be extended and more than anything else you will be a safer diver. The knowledge you have for when planning a dive will also keep those you dive with safer so you will be a better buddy. But most of all you will now be able to dive for extended times beyond the no stop limits of recreational diving.

I started with the question, why should I complete the TEC 40 course when I already have the completed the Deep Speciality?

As a TEC 40 diver I can dive using 28% enriched air to 40 meters for 19 minutes, on air the eRDP gives you 9 minutes.

On 30% I can dive to 36 meters for 26 minutes, the eRDP on air gives you 13 minutes. Even on air I can dive for 18 minutes.

On 21% at 20 meters I can dive for 55 minutes. The eRDP will give you 45 minutes. If I change my gas to 32% I can dive for 100 minutes.

In summary as a TEC 40 diver I can make my dives safer by having more time to spend at my chosen depth and by having redundant systems. I have mastered using these systems which means I am self reliant and can support myself if i get into difficulty.



About altwoodmoon

Leeds United fan. Dog owner, walker and feeder. Qualified scuba diver, Tec diver and PADI Pro. Kids almost flown the nest so have a new life with my wife, loads of holidays. Blogs are my own ramblings but am know to copy (okay plagiarise) other people when they are saying what I want only better but always give them credit.
This entry was posted in Scuba Diving. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s