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Standard Gases

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I often get asked how do you know what mixes of bottom gas to take on a dive? There are two schools of thinking here, Best Mix for the dive or Standard Mixes for a variety of dives.

Essentially Best Mix means you calculate the mix based on the planned depth of the dive. So for a dive to 130′ fsw, at a PPO2 of 1.4, not getting into the narcotic gases and deep air arguments you will undoubtedly hear, the best mix is 28%. For 120 fsw, it’s 30%. You use Dalton’s Diamond to figure out the mix for the depth you want and you mix it.

When I started technical diving, I followed the best mix philosophy. While I still think for a given well planned dive, it works very well and can shave off some deco time… logistically it’s not as easy to be prepared to do a variety of dives. You need to plan the dive and get the fill for that specific dive. With standard gases , you can have a few sets of tanks available to do a wide variety of dives. This is even more true when you get into rebreather diving and bailout tanks, but that’s another article.

The standard gases philosophy is promoted by some of the largest Doing it Right / Dive it Right (DIR) agencies. While they still have a few practical differences between their standards, and if you search the web historically they’ve had even more changes over time… the basic gases are very similar, if not the same.

Below I’ve listed the UTD Standard gases. You can also check out the WKPP Approved Gases page for another nice view of this data (albeit slightly different as it’s GUE, not UTD).

Bottom Gases (Average PPO2 of 1.2)

Gas     ->  Working Range
32%    ->  0′-100′
25/25 ->  90′ – 130
21/35 ->  100′ – 160′
18/45 ->  160′ – 200′
15/55 ->  200′ – 250′
12/60 ->  250′ – 300′
10/70 ->  300′ – 400′

Deco Gases (PPO2 = 1.6)

Gas     ->  Working Range
100%  ->  20′ – 0′
50%    ->  70′ – 30′
35/25 ->  120′ – 80′
21/35 ->  190′ – 130′
18/45 ->  240′ – 200′

Oxygen Breaks

  • UTD: 10 Minutes On / 5 Minutes Off
  • GUE: 12 Minutes On / 6 Minutes Off

Interesting Rationale on selecting these mixes as Standard Gases from a thread with AndrewG (head of UTD, previous training head of GUE):

Look at the original criteria for standard mixes in order of importance:

  1. Must be able to partial pressure blend by adding helium and then topping with Nitrox 32% at a local dive shop
  2. Must have a low PPO2 at it’s max operational depth. 1.2 or less
  3. Must have a buffer zone for safety. If you need to rescue someone or go deeper then there is a buffer.
  4. Must have a narcotic equivalent depth of 100′ or shallower based on the conservative formula of (1-he)*ata”

What to Expect on Open Water Night One

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Typically Open Water Classes are either taught in two ways:

  • Four Days of Classroom & Pool, 1 Weekend of Open Water Dives (e.g. Tues/Thurs, Tues/Thurs & Sat/Sun for Open Waters)
  • Intensive: Two Full Weekends, actually starting on Friday evening.

For the regular four day class, please come prepared to your first night having completed the Knowledge Reviews for the first three chapters of the Open Water Manual.

For the Intensive sessions, you need to be completely DONE with reading the book and ALL of your knowledge reviews before Friday evening.

On your first night we will:

  1. talk logistics
  2. go through our paperwork (ensure it’s signed, filled out correctly, medical releases are in order (if required), etc.
  3. do our Continuous Surface Swim & the Survival Float
  4. learn how to connect your BCD, tank and regulator
  5. potentially complete dives 1 & 2 in the pool

Don’t forget:

  • swimsuit & towel
  • mask, fins & booties and a snorkel [you will also want your gloves for the final day or night so you can practice with them in the in the pool]
  • your Open Water Manual
  • completed knowledge reviews 1-3 (or 1-5)
  • student folder [we’ll fill it out together if you haven’t already completed it]
  • completed medical questionnaire from your doctor, in the event any of the questions were YES

We’ll also be encouraging you to borrow one of the shop wetsuits for the pool, but if you’re planning on going to the tropics anytime soon, buying a 3mm shortie wetsuit before class is a great way to use your own suit in the pool for class.

The Open Water courses include rental scuba gear for open water, so don’t worry about buying all new toys before class. You’ll likely want to chat with us before buying them anyway.

What to Expect on Your Open Water Dives

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We will do Open Waters at Alki Cove 1 or Cove 2 (depending on the crowd). We’ll be having LOTS of FUN, but there are a few things that will make that even more fun:

  • Get some nice warm tea / cocoa / soup and enjoy it before you arrive
  • BRING HOT WATER to warm yourself up (e.g two gallon milk jugs kept in a cooler, or just a cooler full of warm water. You can stand in it and pour the warm water down your wetsuit)
  • Bring food if you need munchies
  • Bring a bottle of drinking water too… you’ll be working and we always want to stay hydrated

Day 1 (Saturday):

  • Two dives to a max depth of 40′, approx 20 minutes each
  • Open Water Gear
    • BCD
    • Regulator
    • 2 tanks (make sure they have enough gas before you leave the dive shop)
    • Weights
    • Wetsuit
    • Booties
    • Gloves
    • Mask, Fins, Snorkel
  • We should be done by Noon on Saturday.
  • Don’t forget to Refill Your Tanks after diving Saturday in preparation for Sunday.
  • Don’t forget to Bring a Passport Photo (for your certification card for Sunday)

Day 2 (Sunday) STARTS at 1PM.

  • Two dives to a max depth 60′, about 20 minutes each
  • Gear (same as Saturday)
  • We need to fill out paperwork Sunday, so we probably won’t be done until about 2p Sunday.

A Day of Diving at Alki

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Diving at Alki Beach Cove 2 in 2010

Critters by time stamp:

  • 00:02     Vermillion Rockfish
  • 00:28     Giant Pacific Octopuses (2)
  • 00:59     Ling Cod
  • 02:28     Little Red Octopuses (4+)
  • 05:23     Grunt Sculpin
  • 05:34     Gunnel
  • 06:37     Cabezon
Stage Bottle Diver

Advanced Trimix Diver

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The TDI Advanced Trimix Diver course is the top level of training for open circuit divers wishing to dive to depths as deep as 100 m / 330 feet utilizing hypoxic levels of oxygen (below 17 percent).  This course is perhaps one of the most informative and challenging and upon completion you are among some of the most elite divers. Your TDI Instructor will teach you

  • Equipment management
  • Multiple stage cylinder labeling and placement
  • Complex decompression planning and contingency planning
  • Dive team awareness and communication
  • Gas monitoring and management
  • Use of travel gasses

The TDI Advanced Trimix manual is one of the most up to date manuals and includes all the latest of technology and practices being used.

Petrel EXT

Shearwater Petrel External

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Rugged Technical Dive Computer

  • 2.4” Full Colour HD Display
  • Air, Nitrox, Trimix
  • External Fischer Connector
  • Monitors PPO2 from 1 or 3 O2 sensors
  • Single AA Battery (Any Type)

Multiple Decompression Algorithms

  • Bühlmann ZHL-16C with Gradient Factors
  • User Adjustable Conservatism
  • Open Circuit, 5 Gases
  • Closed Circuit, 5 Gases
  • Optional VPM-B
  • Gauge Mode

Simple Yet Advanced User Interface

  • 2 Button Push OC Bailout
  • Colour Coded Warnings
  • Simple to Use Adaptive Menus
  • Automatic Screen Brightness

Now with Recreational Nitrox Mode Too

Customizable

  • Metric and Imperial
  • Flip Screen
  • Firmware Updates Via Bluetooth

Dive Logging

  • 1000 Hour Dive Log
  • Free Shearwater Desktop Software
  • Dive Log Downloads via Bluetooth
  • Third-Party Dive Log Software Compatiblity
  • Download software

More Information

Shearwater Petrel 2

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Rugged Technical Dive Computer

  • 2.4” Full Colour HD Display
  • Air, Nitrox, Trimix
  • User Replaceable AA Battery
  • Digital Compass
  • Bluetooth Integration

Multiple Decompression Algorithms

  • Bühlmann ZHL-16C with Gradient Factors
  • User Adjustable Conservatism
  • Open Circuit, 5 Gases
  • Closed Circuit, 5 Gases
  • Optional VPM-B
  • Gauge Mode

Simple Yet Advanced User Interface

  • 2 Button Push OC Bailout
  • Colour Coded Warnings
  • Simple to Use Adaptive Menus
  • Automatic Screen Brightness

Customizable

  • Metric and Imperial
  • Flip Screen
  • Firmware Updates Via Bluetooth

Dive Logging

  • 1000 Hour Dive Log
  • Free Shearwater Desktop Software
  • Dive Log Downloads via Bluetooth
  • Third-Party Dive Log Software Compatiblity
  • Download software

More Information

Shearwater NERD

Shearwater NERD

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The Shearwater NERD (Near Eye Remote Display) is the first technical dive computer with a display mounted on the diver’s rebreather mouthpiece.
This revolutionary device keeps crucial information in your line-of-sight for the entire dive. Thanks to the Micro LCD display and magnifying lens, the data appears as if displayed on a 32” TV screen 12’ away, with no need to focus.

The display is unobtrusive as it virtually disappears when you look straight ahead. The numbers are there when you need them at any point during the dive, and out of the way when you don’t.

The NERD displays the same information as the Petrel technical diving computer, and features the same rugged design, built to withstand the most extreme diving conditions. The device also connects to your desktop computer through Bluetooth, enabling you to keep a detailed dive log and easily download firmware upgrades as they become available.

  • Air, nitrox and trimix decompression computer
  • Open circuit/closed circuit with fixed PO2 and 1 or 3 cell monitoring
  • With fischer connector

Rugged Technical Dive Computer

  • 320×240 QVGA Full Colour Micro LCD Display
  • Air, Nitrox, Trimix
  • Single AA Battery (Any Type)

Multiple Decompression Algorithms

  • Bühlmann ZHL-16C with Gradient Factors
  • User Adjustable Conservatism
  • Open Circuit, 5 Gases
  • Closed Circuit, 5 Gases
  • Optional VPM-B
  • Gauge Mode

Simple Yet Advanced User Interface

  • 2 Button Push OC Bailout
  • Colour Coded Warnings
  • Simple to Use Adaptive Menus
  • Automatic Screen Brightness

Customizable

  • Metric and Imperial
  • Flip Screen
  • Firmware Updates Via Bluetooth

Dive Logging

  • 1000 Hour Dive Log
  • Free Shearwater Desktop Software
  • Dive Log Downloads via Bluetooth
  • Third-Party Dive Log Software Compatibility

NERD Mounting Video

Trimix Diver Manual

Trimix Diver

By | Training | No Comments

As your motivation to explore progresses you will find that you may want to go deeper to dive that wreck that is part of history or that cave system that you have read so much about.

One of the major limiting factors of going deeper is narcosis; TDI’s Trimix Diver course shows how to minimize the effects of narcosis by adding helium to offset the nitrogen in your breathing gas.

While taking the Trimix Diver course your TDI Instructor will teach you how to plan and execute dives utilizing as little as 18 percent oxygen and diving to maximum depth of 60 m/200 feet with a blend of helium appropriate for the planned depth. The course covers topics and skills like:

  • Dive team planning
  • Gas matching
  • Cylinder labeling
  • Surface marker deployment
  • Equipment configuration
  • Thermal protection options
Decompression Procedures Manual

Deco Procedures Diver

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As sport divers planned decompression is not something that we do or have been taught. The TDI Decompression Procedures course prepares you for planned staged decompression diving. With a maximum operating depth of 45m/150 feet, this course is your first step beyond the normal sport diving limits.

Your TDI Instructor will provide you with valuable information and skills, among the topics covered are:

  • Kit set-up
  • Equipment requirements
  • Decompression techniques
  • Decompression breathing gases
  • Gas management
  • Contingency planning
  • Problem solving procedures

The TDI Decompressions Procedures course combined with the TDI Advanced Nitrox course form the foundation of all other technical courses.  After these two courses and some additional experience, the stage has been set for you to move onto additional technical levels.

Some of the materials you will be using include the TDI Divers Guide to Decompression Procedures, US Navy or Buhlmann Air Decompression Tables (made of vinyl for easy in-water use and storage)