This is the DeeperBlue.com Beginners Guide to Scuba Diving. We’ve put this guide together to help budding Scuba Divers understand what is required to get started. Part 20 of this series takes a look at Tec Diving Expanding Beyond Recreational Scuba.
Tec Diving Expanding Beyond Recreational Scuba
Tec divers, you may have seen them on one of your dive boats. They look like they came out of a sci-fi “B movie”, a half a dozen tanks hanging off them, gear attached to all the d-rings and moving like something you imaging from outer space. You whisper a question to another diver, what are they doing? You get a flat mono-tone answer, “they are Tec divers”, as if that is all the explanation you would need. Tec.
To many recreational divers, the world of technical diving is something to aspire to. To others, it represents a higher risk that they are not willing to take, and often cannot understand why others would risk it as well. Technical diving, or as it is generally called Tec, has no real definition. The best definition of Tec is that it is beyond recreational scuba diving. While not an accurate answer, some will say Tec diving is decompression diving.
Tec divers go deeper and stay longer, decompression dives are their standard dive, and they may manage different gas mixtures on a single dive. The tolerance for errors are small and mistakes when they happen are often fatal. To many, this might make the Tec diver seem reckless even suicidal. On the contrary, Tec divers may love the adventure and risk, however, they pay close attention to details, everything has a back up and they are well trained.
Technical divers are often specialist, leaning towards their favorite style of diving and choice of equipment. Close circuit equipment, commonly called rebreathers, are used by some divers. This reuses the air supply filtering out carbon dioxide and adding oxygen greatly extending the air supply. Others will still use open circuit equipment, which scuba is, but use different mixes of gasses at different concentrations to avoid the effects of oxygen toxicity and other gas particle pressure problems. When talking in general terms of the contents of their cylinders, the term breathing gas or breathing gasses are used. The Tec diver may have started as a scuba diver but now the equipment they use is very specialized.
Realms of Technical diving
Les’s take a quick look at some the different items we will find in the realm of Tec diving
Recreational divers are taught never – ever – exceed the NDL. To the Tec diver it is just a point of reference that their decompression plan is based on. Don’t tell your dive instructor I told you this, but in reality every dive is a decompression dive. The concept of the NDL is that you will return to the surface no faster than a given rate, 60 feet per minute. While you are ascending at this rate, you are doing a rolling decompression. You are moving slow enough and the amount of nitrogen in your system is low enough that the decompression does not need you to pause to catch up. When you exceed the NDL, it just means that the rolling decompression is not enough and a mandatory decompression stop or a deco stop is needed. You may in fact need more than one stop.
As mentioned in another article, decompression diving can become difficult to manage because you also have to manage your breathing gas. Decompression divers will often use different sets of breathing gasses at different depths to shorten the over all dive time. This can made decompression planning difficult.
Mix Gas diving
When you learned scuba diving, you used compressed air, the same that you breath every day excepted filtered for water content and pollutants. Later you might have moved up to Enriched Air Nitrox (EAN). This reduced the nitrogen in our system giving us a longer bottom time before hitting the decompression limit, but the trade off was that we could not go as deep. One of the areas of diving for Tec divers is Trimix. While EAN changes the ratio of oxygen and nitrogen by adding oxygen, Trimix changes the ratio by adding helium. Trimix is a breathing gas with helium, oxygen and nitrogen. Changing the percentages between the three gasses will help us manage the effects of oxygen and nitrogen on our bodies.
Close Circuit Equipment
Scuba is an open circuit configuration. We have our breathing gas in our cylinders, we inhale it and when we exhale it leaves the circuit. Close circuit systems will reuse the air. It is a complex operation but has a simple explanation. The generic term for a close system is a rebreather.
When we breathe, the body absorbs oxygen from the lungs and sends carbon dioxide to the lungs to be expelled. However, we do not absorb all the oxygen. The air we inhale at the surface is 21% oxygen and .04% carbon dioxide (depends on pollution). When we exhale the oxygen is around 16% and carbon dioxide is 4%. When diving with a rebreather, the air we exhale is returned to the rebreather where it passes through a carbon dioxide scrubber to remove that gas and goes back into storage. The air in storage is monitored for oxygen content and additional oxygen is added when need to bring it back to the level we demand. This can give us a supply of breathing gas that can last a long time. Diving a rebreather requires different types of calculations than open circuit. Setting up the rebreather to use requires special training and Tec divers certified as rebreather divers are only certified on the model they were trained on.
There are many specialties within the realm of Tec diving, but nothing yells technical diving more than cave diving. Cave diving is unlike any other type of diving you will ever encounter. Divers can go hundreds of meters into a flooded cave system. At time they may be in large areas and others in tunnels they can barely fit in. The techniques of cave divers such as the rule of thirds, side mounts and running lines, may have transferred to other technical diving and recreational diving but that does not make you qualified to enter a cave. Sadly, many recreational divers ignore warning of enter caves untrained and die each year. Cave diving is a progressive series of courses taking you from the cavern diver to one who can freely explore caves. Knowing their limits is a key trait for an experience cave diver.
Like to become a Tec Diver?
It used to be that the line between recreational diving and Tec diving was clear. The recreational accreditation agencies only taught scuba. Technical certification agencies only taught Tec. Only a few agencies, themselves special purpose taught both. Mergers, acquisitions and technology advancements has blurred the line. Recreational and Tec agencies have either merged or expanded into the other realm. You will find that there is now a sort of in-between area. PADI and SSI both have courses that teach single stage decompression using Nitrox and oxygen. However, still within the depth of recreational diving and using standard scuba diving gear and a side tank. Other agencies have similar programs. The courses are a great way to start into Tec. First, however, you need to develop and hone your skills so that you are ready for the task.
Being a scuba diver, whether it is an Open Water Diver or a Technical Cave diver, is a world that is filled with many exciting things. Learn to dive, dive as often as you can and expand your diving skills as they will in turn expand the horizons of your life.
Continue reading more from the DeeperBlue.com Beginners Guide to Scuba Diving.