How to Get Into Technical Diving: Courses, Prerequisites and Costs

What makes a dive technical?

A dive is technical when you cannot go straight to the surface, or when depth, gas or equipment go past recreational limits. PADI describes it as diving beyond recreational no-stop limits, and a post on its blog lists four markers: depths beyond 40 m (130 ft), overhead environments more than 60 linear m (200 ft) from the surface, planned decompression, and varied gas mixes or closed-circuit rebreathers. Our other course articles are collected under Training & Certification.

Agencies draw the lines slightly differently. DAN's definition, written by Karl Shreeves in 2014, puts the overhead limit closer: wreck or cave penetration beyond 130 linear feet (about 40 m) from the surface. DAN also explains why the extra training exists. With an hour of decompression ahead of you, or a cave ceiling above, you cannot ascend immediately when something goes wrong, and DAN notes that the chain of errors leading to a serious accident is much shorter than in recreational diving.

Gas switches arrive with the first decompression course. You carry a second cylinder with a richer mix for the stops: PADI Tec 40 allows up to 50% oxygen as a decompression gas, and SSI's Extended Range Nitrox allows up to 100%.

Are you ready? Prerequisites for your first tech course

On paper you need a second-level card, nitrox and deep training, and 24-30 logged dives. The logbook matters more than the cards, because a decompression course assumes your buoyancy and gas awareness already take little thought. Dive centres can also set a higher bar: Horizon Divers in Key Largo lists 40 logged dives for its Tec 40, 20 of them on nitrox and 10 deeper than 30 m. The agency minimums:

• PADI Tec 40: Advanced Open Water, Enriched Air, and Deep Diver or proof of 10 dives to 30 m (100 ft); 30 logged dives; age 18; a medical form signed by a physician in the last 12 months. PADI's TecRec blog adds that 10 dives should be on enriched air deeper than 18 m (60 ft). Rescue Diver is recommended for Tec 40 and required for Tec 45; our guide on when to take the rescue course covers that step.
• SSI Extended Range Nitrox: Deep Diving and Enriched Air Nitrox 40 certifications and 24 logged dives, plus SSI's Sidemount Diving certification if you train in sidemount.
• TDI Decompression Procedures: an advanced-level card, 25 logged open water dives and a minimum age of 18.
• GUE Technical Fundamentals, the step before Tech 1: certification to 30 m, 75 non-training dives after your entry-level card, 25 of them deeper than 21 m (70 ft), and 25 in doubles (or 15 after GUE's Doubles Primer). Minimum age 16, and GUE accepts only non-smokers.

Technical diving certification paths compared

DAN describes three open-circuit levels: decompression on air or nitrox to about 130 ft (40 m), trimix to about 200 ft (60 m) and hypoxic trimix to about 300 ft (90 m). The agency ladders follow that shape in smaller steps. The first rung differs most. PADI and SSI start with a capped amount of decompression, TDI starts at 45 m, and GUE brings helium into its first decompression course. CMAS lists a Technical Skills Diver course as the recommended first step for all its technical programmes.

Dive counts climb quickly. PADI asks for 30 logged dives for Tec 40, 50 for Tec 45 (10 deeper than 30 m) and 100, or 75 hours, for Tec 50. That is 70 more logged dives between Tec 40 and Tec 50. TDI's Trimix and Extended Range courses, PADI's Tec Trimix 65 and GUE's Tech 1 all want 100, and CMAS asks for 150 before normoxic trimix.

In what order should you train?

Skills first, then decompression, then depth and helium. Each of the four big technical systems has a no-decompression course or session for this first step. TDI's Intro to Tech covers buoyancy, trim, situational awareness and technical gear in at least 3 dives no deeper than 23 m (75 ft), and accepts divers from 15 with parental consent. SSI's Extended Range Foundations is four confined water sessions on buoyancy, trim, finning and positioning, and its digital kit is listed at €125. GUE's Technical Fundamentals runs over four days with at least eight dives, and can only be done in doubles. PADI's Discover Tec is a short introduction in confined water.

The skill bar is specific. TDI's Decompression Procedures standard asks you to hover at a fixed position without moving hands or feet. GUE's Tech 1 standard uses a reference of no more than 20 degrees off horizontal while staying within 1 m (3 ft) of a target depth. If that is not yet easy, fix it before paying for a decompression course; our buoyancy and trim guide has drills for it.

After the first decompression course, the agencies split on air at depth. TDI's Extended Range course trains air dives to 55 m (180 ft) with staged decompression. GUE uses helium to reduce narcosis from Tech 1, which stops at 51 m. On air, the equivalent narcotic depth is the depth itself, so a 55 m air dive is a 55 m narcotic exposure.

Which gases will you use? A worked example

Each rung adds a gas, and the arithmetic is the MOD and END maths you know from nitrox. The limits used here are the ones in the CMAS trimix standard: a ppO2 of 1.4 bar at the bottom and 1.6 bar on decompression stops.

Take a 40 m dive at Tec 40 level. The absolute pressure is 40 ÷ 10 + 1 = 5.0 bar, so the best bottom mix is 1.4 ÷ 5.0 = 0.28, or EAN28, with a MOD of exactly 40.0 m. The decompression gas at this level is EAN50: at 1.6 bar its MOD is (1.6 ÷ 0.50 − 1) × 10 = 22.0 m. Pure oxygen, allowed from Tec 45, reaches 1.6 bar at 6.0 m. Our nitrox calculator gives the same figures.

Trimix adds a second decision: how narcotic you accept the dive to feel. For 60 m at 1.4 bar, oxygen is 1.4 ÷ 7.0 = 20%. Counting oxygen as narcotic, an END of 30 m needs 1 − 4.0 ÷ 7.0 = 42.9% helium, rounded up to 43%, so trimix 20/43. An END of 40 m needs 1 − 5.0 ÷ 7.0 = 28.6%, rounded up to 29%, so 20/29. Both limits appear in real standards: TDI's Advanced Trimix standard sets a maximum END of 30 m on all trimix dives, while the 2009 CMAS normoxic trimix standard allows 40 m. Our trimix calculator runs both narcosis conventions.

What gear changes for technical diving?

More cylinders, and a spare for anything you cannot do without. The course standards spell it out:

• Doubles or sidemount. PADI Tec 45 uses double cylinders in back mount or sidemount, SSI's Extended Range Nitrox a twinset or XR sidemount system with one stage cylinder, and GUE doubles joined by an isolator manifold so each cylinder has its own first stage.
• A backplate and wing. GUE's base configuration is a backplate on one continuous piece of adjustable webbing with a crotch strap, and a minimalist back-mounted wing sized to the cylinders.
• A long hose. GUE puts the primary second stage on a 1.5-2 m (5-7 ft) hose with a necklaced backup on a short hose. TDI's trimix standard asks for a long hose rigged for gas sharing at depth.
• Decompression cylinders, each labelled and fitted with its own regulator and pressure gauge. TDI's trimix standard asks for 1.5 times the gas the planned decompression needs.
• Redundant depth and time. TDI's trimix standard requires redundant depth and timing devices, and an air computer with a gauge mode can serve as one of them.
• Smaller items: a surface marker buoy with a reel or spool (GUE sets at least 30 m of line), a cutting device, a backup mask, wetnotes, and an oxygen analyser. TDI recommends a helium analyser for trimix.

How long does it take and what does it cost?

Most courses below take three to six days, and the shops list US$900-2,000 per course. Prices vary by centre and country, and so does what the price covers. Louisville Dive Center, for example, excludes all gas fills (including the instructor's) and rents full tech gear at $150 per course phase, a deco bottle at $50 and a deco regulator at $55. CMAS tells trimix students to bring equipment they already know, because the course is not a place to try new gear.

At Horizon Divers the PADI ladder to Tec 50 comes to $2,800 in course fees, or $4,400 with Tec Trimix 65, plus $75 per course for rental gear. The time between courses counts as well, since the minimums rise to 100 logged dives before Tec 50. A post on PADI's blog calls tec diving a commitment in cost (extra equipment and gas blends) and in time.

How risky is technical diving?

Higher than in recreational diving, and experience does not make it go away. A French study published in 2026 reviewed 124 technical divers treated at five hyperbaric units between 2010 and 2024. They were not beginners: among those who reported it, the median diver had 20 years of diving and about 1,000 logged dives. The median maximum depth was 53 m, 76% were on rebreathers and 62% on helium mixes. Decompression sickness made up 105 cases, and a quarter of those ended with an unfavourable outcome, mostly involving bone or the inner ear.

Only 23.6% of the incidents involved a recorded procedural error, so about three in four happened without one. The errors that were recorded were mostly fast ascents, buoyancy problems or missed stops, which are the basic skills the first decompression courses drill.

DAN's advice is to look for structured training with an experienced instructor, respect your limits, and accept that tech diving is not for everyone. PADI's TecRec blog says the right time is when you are ready, and that it takes discipline and commitment. GUE makes insurance that covers hyperbaric treatment a Tech 1 prerequisite.

Rebreathers: a separate path

A closed-circuit rebreather (CCR) recycles exhaled gas, so depth barely changes how much you use. DAN gives the scale: a 300 ft (91 m) dive takes more than 140 cubic feet of gas on open circuit and less than 5 on a CCR. Agencies train it as its own ladder, such as PADI's Tec 40, 60 and 100 CCR courses and SSI's CCR programmes to 30, 60 and 100 m.

The risk profile differs. Andrew Fock's 2013 analysis of 181 recreational rebreather deaths between 1998 and 2010 found a death rate about 10 times that of open-circuit recreational divers, and a 25-fold higher risk of component failure than a manifolded twin set, which a bailout system can offset. Two-thirds of the fatal dives involved a high-risk dive or high-risk behaviour. A 2026 DAN review counted 241 confirmed CCR deaths in 2013-2022, a mean of 24 a year, mostly on dives to 40-80 m, and estimated 1.8-3.8 deaths per 100,000 CCR dives from limited data.