TDI (Technical Diving International) agency was founded in 1994 and is now the world's biggest and most advanced school of technical diving, which can be supported by data on the current world number of certified "Nitrox Divers" in several of the biggest schools of diving:

(According to data of technical diving magazine "Immersed", November 2002 Vol.7, No. 3)

One can ask: "Why TDI?" And really, why take this Nitrox course in the specialized TDI federation when any amateur federation such as PADI, NAUI, CMAS etc. also include the Nitrox-diver course on their menu?

It is not technical diving any more and the Nitrox is not a dangerous respiration mixture for the "extremes" as considered just not long ago by the biggest amateur federations. Quite the reverse, the Nitrox is today acknowledged as a factor considerably increasing underwater safety and the general state of a scuba diver: indeed, if you know how to use it. Statistical data show that dives with Nitrox were double those made with oxygen in US during last year.

In any amateur federation such as PADI or NAUI, the course of Nitrox diving is just one of numerous specialties, the same as diving from a shipboard or around a reef. It's a kind of deadlock: you've got the Nitrox course completed, so what's next?

It's totally different with TDI. The basic TDI course is a fundamental course of technical diving, which leads to the infatuation on deepwater immersions, penetrations into caves and wrecks. The TDI Nitrox course is the start of a great way: through courses of decompression procedures and dives with advanced limits to the deep-sea swimming on trimix. Anyone of you can stop at the stage you like most, realizing that you're not personally interested in or afraid of going on. Still you can move forward to new knowledge, personal achievements and feelings. Your way here will depend on you solely. The one common thing with the different people's ways is they all start with the Nitrox course.

Advantages Of Diving With Increased Oxygen Mixtures or "Nitrox"

Nitrox is a mixture of gases where the content of oxygen is higher than that in the air (21%). Each diver knows that the time of being in the depth and general health state is effected by nitrogen that is a component of the air.

If a diver is in the depths for a long time, his body absorbs nitrogen and he must hold within certain time limits in order to be able to surface without "decompression".

If we breathe air with increased oxygen content and, therefore, we inhale less nitrogen, the "decompression less" diving time rises considerably. For instance, using "Nitrox" 40 % as the underwater respiration mixture allows 55 minutes at 25 metres' depth without decompression while breathing the air could only provide 28 minutes at such a depth without decompression. In other words, this time actually doubles. Besides, diving with Nitrox and using tables for air, the safety of diving could be essentially increased.

Thus, the major advantage of using Nitrox is the increased safety of immersions realized for longer times at depth, reduced surface intervals, and lesser time before flight; in addition, many divers report they are less tired after diving on Nitrox.

TDI Technical Diving Courses

Safe diving to great depths requires the completion of corresponding courses. All of them constitute the sphere of the so-called technical diving: diving under non-standard conditions of increased complexity often requiring the additional technical equipment. Like in recreational scuba-diving, the training consists of a number of courses arranged in accordance with the principle "from the simple towards the complex" where each next step brings new knowledge and discoveries.

Deep Diving Courses

Courses of Diving Into
Confined Environment

The cited price of the courses is the full cost and includes theory, practical studies, outfit rental and the cost of the certificate.

Nitrox, Advanced Nitrox, Decompression Procedures, Semi-Closed Rebreather (Dolphin/RAY) courses are available in Latvia in the warm season (Nitrox at any time of the year) while you are welcome to Khurghada to take other courses arranged by us jointly with the diving centre Diver's Lodge and TDI Instructor Trainer Arthur Zaloga.
More details available by phone and E-mail.

In recent years Nitrox diving have become so popular throughout the world that the offer thereof as a service determines the choice of a diver's centre or a safari-boat while availability or absence of Nitrox has become a business card for many diving operators. Naturally, Nitrox owes such widespread use to its approval by PADI Federation, until which Nitrox immersions were considered dangerous and risky procedures in the sphere of technical diving and were severely criticized by conservators avoiding the risks of innovations. Currently, Enriched Air Diver PADI and Nitrox Diver CMAS, IDD as well as courses of other organizations issuing certificates have become an integral part of scuba-diving training. Nevertheless, we consider this course in the system of technical diving as from this course starts deepwater diving.

This comparatively short and simple course amateur teaches divers how to plan and perform dives with Nitrox: an air mixture enriched by 21% to 40% oxygen. Methods of diving differ little from those with the compressed air while planning of immersions is radically different as, apart from the decompression limit, a rigid oxygen limitation of depth appears.

Therefore, the course includes teaching calculation of immersion mode and determination of partial oxygen pressure in tissues.

Regular outfit is used: regulators, compensators, wetsuits etc. Depending on the type of compressor and the method of composing the gas mixture, especially purified or ordinary cylinders are used. Nitrox cylinders must be marked by green stripes or green valves with label indicating the mixture composition and the depth limit. Besides, especially purified cylinders must bear EAN (Enriched Air Nitrox) marking.

At the end of the theoretical course 2 to 4 training Nitrox dives are recommended, however, it is not mandatory. After completion of the Nitrox-course you can learn diving with semi-closed cycle rebreathers, as well as go to the Advanced Nitrox Course.

At this stage a diver can dive with Nitrox of any oxygen percentage down to 45 metres. It requires exact observance of the depth limit and perfect command of neutral buoyancy. For example, the depth limit is 6 m when diving with pure oxygen. If a diver goes lower due to seas or some problems with the outfit or just through mere carelessness, a syndrome may occur with the central nervous system being poisoned with oxygen. Not only purified and properly marked cylinders are used, but also oxygen regulators marked in green where sealing rubber rings are replaced with those made of fluroplastic and the first stage does not contain silicone. Highly oxygen-enriched air is rarely used for the main diving. Most often it is breathed at last decompression stops after long deepwater dives. Stops with 50% Nitrox are made at depths from 18 m, while with EAN70 they start from 12 m and not lower than 6 metres with pure oxygen. Sometimes at frequent dives resulting in considerable accumulation of residual oxygen in tissues, evening and night dive completing the long "diving" day are made with 50%-oxygen (or, less often, 70%) Nitrox.

Minimum number of dives for passing the course is 25 and the minimum starting age is 15.

The course of decompression procedures could be logically featured as an epoch-making one. This is a very serious step on the way to becoming a real diver who is making many dives, intelligent and aware of the real risks. After completion of the course the decompression ceases to be a monster to be afraid of. This is an ordinary phenomenon with a certain type of diving. The course of decompression procedure is intended to master the technique of diving with decompression. Planning and exact following the developed schedule make up the lion's share of the programme. After lasting diving at 30 metres and deeper and slow surfacing, which itself is decompressioning, desaturation is not sufficient to provide safety and therefore fixed stops for a certain time are to be made at some depths. It is called a step decompression. Decompression stops are just what makes technical decompression diving different from amateur diving without decompression; and reasonable scheduling of such stops is the purpose of the decompression procedure course.

Practical exercises consist of fulfilment of the developed schedule in real conditions. Along with major air cylinder (or paired cylinders) behind the back, the decompression cylinder with 7 or 10 litres of 50% Nitrox is hooked by snap hooks to the compensator straps at the front side. The minimum number of logged dives for passing the course is 25 and the minimum starting age is 18.

Extended Range actually means extended limits. ER dives are made at depths down to 55 metres with compressed air plus 50% Nitrox or pure oxygen for decompression. Conditions may be very different: vertical walls, caves, wrecks, cold, strong current etc. ER dives are most often made along vertical coral or rocky walls. Passing of the course requires not less than 100 logged dives, knowledge of Decompression Procedures Diver and experience of decompression dives. Minimum age is 18. The course includes exercises for development of self-sufficiency, skilful use of outfit and endurance.

Practical lessons consist of exercises on shallow water, at depth and decompression dives down to 60 metres, with integrated exercises on and simulation of emergency situations. Paired cylinders with separate regulators are used in the course. The pairing must have a separating valve making both cylinders autonomous. Waistcoat-compensator must have two bags and two inflators, on the left and on the right. It can be either DiveRite Super Wing or OMS with rigid back and two inflators, or any other technical compensator having no less than 20 l capacity, backup air chamber and second inflator. Decompression 7 l or 10 l cylinder with thereto fastened buoy and reel is snap-hooked to metal rings of the compensator. A map case with the dive plan is attached by a snap-hook either to the cylinder or to the compensator rings, or is put on the hand, which is most convenient for you. That is the outfit in which the practical part of the course is mastered, upon completion of which a candidate will have to pass a written test consisting of several parts and properly perform an examination diving according to a self-made plan.

This is the initial course of deepwater diving down to 85 metres with the use of Trimix: helium-air mixture of various percentages between oxygen, nitrogen and helium. The course consists of theoretical and practical lessons on planning, preparation of outfit, analysis of mixture and exact following the developed plan under the water.

Minimum number of logged dives for passing the course is 150 and student divers must have reached 18.

Paired cylinders with separate regulators are used in the course. The pairing must have a separating valve making both cylinders autonomous. Requirements to the waistcoat-compensator are the same as in ER course. Decompression 10 l cylinders (7 l also may be used) are snap-hooked to the breast and belt metal rings from the left and from the right, bearing thereon fastened additional equipment and accessories : buoys with reels, lamps (if necessary) etc. Left regulator would desirable have a long two-metre second-step hose for emergency breathing of partner whose respiration mixture was exhausted at the depth.

Plan of dive with Trimix provides descending to 20 metres with Nitrox or to 30 metres with the air (as Trimix contains too little oxygen for breathing on surface and in shallow water) followed by switching over to the major helium mixture with which the main stage of dive is made. During surfacing, switchover from Trimix to Nitrox or compressed air is made starting from 40 to 30 metres, and at 20 metres 50% Nitrox is switched on instead in order to speed up decompression. After deepwater dives pure oxygen is often switched on at 6 m for quicker decompression. Currently the use of compressed air as a respiration mixture is generally excluded where possible, as the switchover from Trimix to air results in strong narcotic shock which is felt like falling down to a great depth. Besides, small additional air cylinder is often used: not for breathing but for blowing under the dry suit and the compensator. Such dives require at least two computers, preferably technical ones; however, good "air" computers will also fit quite well provided they will be closed into compression mini-chamber to prevent their switch-off resulting from violation of decompression condition, or hanged under the boat until complete desaturation.

This more complicated version of the preceding basic course allows descending with Trimix without depth limitation and is intended for the perfection of professional skills. If you feel yourself strong enough for a really deepwater diving, you can make it, having worked out your detailed route for visiting the Abyss and looking straight into its eyes...

The course familiarizes divers with regenerative outfit and opens amazing perspective of lasting dives with rebreathers. When diving with rebreather, you at last get to know what really is the world of silence; and it cannot be done with a regular aqualung: frequent exhales of several people accompanied by ringing sound of exhaled bubbles turn the underwater realm into a noisy park and frighten off denizens of the deep, especially big mammals such as dolphins, whale sharks and seals. In their company you can only swim with a breather or a rebreather. Many people wrongly think that dives with a semi-closed rebreather are deepwater; however, it is not so: we actually dive with Nitrox, only the resource of respiration mixture is tripled due to its partial recirculation in the system. While diving with aqualung we exhale the used air outside and thus do not utilize a considerable share of oxygen at all, here we regenerate it with"fresh" oxygen.

This training course teaches the skills of correct use, disassembly and check of rebreathers, analysis of mixture in a cylinder, calculation of respiration mixture composition. Dives with semi-closed rebreathers are restricted to a depth of 40 metres. A student must have previously passed the Nitrox course and reached the age of 15. The course consists of theoretical and practical lessons in the sea.

A special introductory course intended to acquire skills, experience and knowledge necessary for short penetrations into caves and other underwater caverns having a "roof" above the head. After completion of such course diver can dive into caves where the daylight is still glimmering and the exit is within visible limits, however, not further than 61 metres from the exit and provided that the water transparency is not less than 12 metres. Maximum depth of this decompression less dive is 40 metres. To join the course, a diver must have made no less that 20 dives and reached the age of 18 or 15 if in the presence of parents. Regular outfit is used, like that in open water immersions, with the only difference that a lamp must take and respiration breather may not be attached to the facemask. The only actually new skill to be trained is the use of the route line: it's lying from the reel, fastening on walls, moving along the line and emergency actions if the line is lost.

A special introductory course on deep penetration into caves under heavy conditions with the air. Diving into caves at this level is done with a single cylinder no deeper than 40 metres, without decompression and at water transparency not less than 10 metres. The cylinder must have a V-shaped valve block for the connection of two regulators, main and backup. Other necessary appliances : three lamps (one major powerful and two backup), reels with the route line about 107 metres and safety reels with 30 metres long line; facemask without breather; diver's knife. Participation in the course requires not less than 25 performed dives, completion of the preceding course and minimum age of 18 or 15 if in the presence of parents. Penetrations are made at depths down to 40 metres, possibly with decompression, without putting on/taking off the outfit, i.e. not penetrating narrow passages or culverts. Minimum number of registered immersions for passing the course is 100 and the minimum accepted age is 18.Configuration of the outfit is similar to that in the preceding Cave course.

This course enables decompression penetrations into deepwater caves with culverts and labyrinths. The immersion with the compressed air using Extended Range methods is made until the depth of 55 metres while dive with Trimix is not restricted by the depth. Serious penetrations into deep cave are the subject of specialized cave underwater federations, such as NACD, NSS, CDAA, CDG, dealing solely with the technique of complicated cave diving, releasing their own textbooks and films, arranging their own festivals and conferences. But it is a separate sphere of underwater activities...

A special course on deep penetration into holds of wrecks according to the level of teaching after the deepwater qualification system: down to 40 metres with the air for all amateurs or "decompressionists" and to 65 metres with the air and use of ER methods or with Trimix. Minimum number of logged dives is 50 and the minimum student's age is 18.

Paired cylinders with separate regulators are used in the course. The pairing must have a separating valve making both cylinders autonomous. Waistcoat-compensator is the same as in ER course (see above). Decompression cylinder 10 l or 7 l with a mounted buoy and reel may be, if so necessary, attached to the metal rings of the compensator by means of snap-hooks. Apart from it, two reels are required with the penetration line and safety line and at least two luminaries. The practical course includes exercises on the use of reels with lines and their fastening during deep penetration into the wreck.