Unit 1 - Introduction Student Performance: By the end of the lesson you will be able to: Describe what nitrox is. List other names for nitrox. State the early history of diving with gases other than air. State when NAUI sanctioned nitrox diving. Describe what nitrox is not. Unit 1 - Introduction Unit 1: Introduction What is Nitrox A Bit of History Why Dive with Enriched Air Nitrox Common Misconceptions About Nitrox Terminology Unit 1 - Introduction What is Nitrox? Nitrox is air in which fraction of nitrogen is reduced Nitrox is also called: Oxygen-enriched air Enriched air nitrox EAN x Reducing Nitrogen Increasing Oxygen Unit 1 - Introduction A Bit of History Development of nitrox use Early research and use Controversy NAUI endorsement of EAN X NAUI Standards for EAN X training Unit 1 - Introduction Common Misconceptions About Nitrox Myth 1: It is hard to dive with nitrox. Myth 2: Nitrox is for technical diving. Myth 3: Nitrox is for deep diving. Myth 4: If you dive with nitrox you wont get bent. Myth 5: Nitrox is safer than air. Myth 6: If you dive with nitrox you wont get narcosis. Unit 1 - Introduction Why Dive With Enriched Air Nitrox Extended Dive Time Unit 2 - Gases & Gas Mixtures Unit 2: Gases & Gas Mixtures Gas Basics Whats in Air Some Facts About Individual Gases How Gases Behave Converting Between Depth and Pressure Calculating Partial Pressures Unit 2 - Gases & Gas Mixtures Student Performance: By the end of the lesson you will be able to: State the composition of air. Describe how gases behave. Explain the relationship between pressure and gas volume. Describe the solubility of gases. Explain what partial pressure is and determine various partial pressures. Determine absolute pressure at depth. Determine the partial pressure of a gas in a mixture at depth. Unit 2 - Gases & Gas Mixtures Gas Basics Matter Composition of a gas Gas mixtures Gas pressure Dissolved gases Unit 2 - Gases & Gas Mixtures Whats in Air? Composition of air Oxygen (O 2 ) Nitrogen (N 2 ) Argon (Ar) Carbon dioxide (CO 2 ) ~ (average) Others Simplifying the numbers: 21% oxygen / 79% nitrogen Unit 2 - Gases & Gas Mixtures How Gases Behave Daltons Law: Partial Pressure in Gas Mixtures Henrys Law: Solubility Boyles Lay: Pressure and volume Unit 2 - Gases & Gas Mixtures Converting Between Depth and Pressure Absolute vs. gauge pressure Gauge Unit 2 - Gases & Gas Mixtures Converting Between Depth and Pressure continued Converting by formula To find absolute pressure: P ata = (D fsw / 33 fsw/atm) + 1 atm = (D fsw + 33 fsw) / 33 fsw/atm To find depth: D fsw = (P ata 1 atm) x 33 fsw/atm Unit 2 - Gases & Gas Mixtures Calculating Partial Pressures If you know the absolute pressure: The basic formula: P g = F g x P total Using a graphical figure Unit 2 - Gases & Gas Mixtures What is the PO2 of EAN38 at 34 msw (112 fsw)? Pg = Fg x Ptotal 0.38 * 4.4 atm = 1.67 ata Unit 2 - Gases & Gas Mixtures Calculating Partial Pressures continued Moving between partial pressure and depth using formulas: Depth to partial pressure First find the absolute pressure at depth. Then find the partial pressure of the component gas at that absolute pressure. Partial pressure to depth First find the absolute pressure of the gas mixture from the partial pressure and fraction of the component gas. Then find the depth for that absolute pressure. Unit 2 - Gases & Gas Mixtures Calculating Partial Pressures continued Using a table Unit 3 - The Physiology of Diving Nitrox Unit 3: The Physiology of Diving and Nitrox Narcosis Decompression Sickness Physiological Effects of High Oxygen Levels Unit 3 - The Physiology of Diving Nitrox Student Performance: By the end of the lesson you will be able to: List the physiological effects of nitrogen in diving. State physiological effects of low oxygen levels. List the physiological effects of high oxygen levels. Recite signs and symptoms of oxygen toxicity. State limits of hyperbaric oxygen exposure. Unit 3 - The Physiology of Diving Nitrox Nitrogen Narcosis The mechanisms of nitrogen narcosis are similar to that of gases used in general anesthesia. Divers may not be aware that they are impaired. There is no appreciable benefit to breathing nitrox. Ascent to a shallower depth is all that is required. Unit 3 - The Physiology of Diving Nitrox Decompression Sickness What causes it DCS signs and symptoms Unit 3 - The Physiology of Diving Nitrox Decompression Sickness continued How to avoid DCS Treatment for DCS NITROX REDUCES THE RISK OF DCS. IT DOES NOT ELIMINATE IT!!!!!!!! Unit 3 - The Physiology of Diving Nitrox Oxygen: The Good and the Bad Is necessary to sustain life Too high an oxygen level can be just as harmful as too low Oxygen is our life-support gas The primary waste product is carbon dioxide Oxygen and Metabolism Unit 3 - The Physiology of Diving Nitrox Physiological Effects of Low Oxygen Levels (Hypoxia) Hypoxia means low oxygen symptoms begin to appear if the partial pressure of inspired oxygen falls below about 0.16 atmosphere Onset of symptoms at a PO 2 of about 0.16 ata Signs and symptoms include impaired mental performance and defective memory, blueness of the lips (cyanosis), fatigue, visual disturbances, and dizziness Unit 3 - The Physiology of Diving Nitrox To avoid Oxygen Toxicity we have Partial Pressure Limits The generally accepted limit for nitrox diving is: 1.4 ata PO 2 1.6 ata PO 2 as a contingency 1.4 ata PO 2 is more than adequate for 99.9% of the dives you may want to accomplish. Unit 3 - The Physiology of Diving Nitrox Physical Effects of High Oxygen Levels Central Nervous System Toxicity has a wide range of signs and symptoms, the most dramatic being epilepsy-like convulsions CNS toxicity can result from relatively short exposures to high partial pressures of oxygen Pulmonary Toxicity or Whole Body Toxicity results from prolonged exposure to elevated partial pressures of oxygen (above about 0.5 atmosphere) not a concern for recreational nitrox diver Unit 3 - The Physiology of Diving Nitrox Central Nervous System Toxicity Factors that can increase your susceptibility to CNS oxygen toxicity heavy exercise, increased carbon dioxide build-up, chilling or hypothermia, and water immersion One cannot predict oxygen toxicity Unit 3 - The Physiology of Diving Nitrox Central Nervous System Toxicity continued Central Nervous System Toxicity The mnemonic acronym ConVENTID is useful for remembering the most obvious of them: Convulsions Visual disturbances Ears Nausea Twitching or Tingling Irritability Dizziness or Dyspnea Unit 3 - The Physiology of Diving Nitrox Central Nervous System Toxicity continued Central Nervous System Toxicity Convulsions are the most obvious and most serious signs. Possible precursors to convulsions are: Visual disturbances, tunnel vision, dazzle or seeing fireflies. Ear ringing, tinnitus, or sounds like an approaching train in a tunnel. Nausea, including vomiting. Twitching, especially of the lips and small facial muscles or the hands, or tingling (paresthesia) especially in the fingers. Irritability, restlessness, euphoria, dysphoria (uneasiness or feelings of impending doom), anxiety, or general confusion. Dizziness and vertigo or dyspnea (difficult or labored breathing). Unit 3 - The Physiology of Diving Nitrox Managing Oxygen Exposure The best way to avoid oxygen toxicity problems is to stay within correct oxygen exposure limits. Unit 3 - The Physiology of Diving Nitrox Managing Oxygen Exposure continued NOAA Oxygen Exposure Limits In addition to a general PO 2 limit, NOAA has oxygen exposure time limits for a range of oxygen partial pressures from 0.6 ata to 1.6 ata PO 2 =1.4 ata 111 on EAN 32 Unit 3 - The Physiology of Diving Nitrox Avoiding CNS Toxicity CNS toxicity is avoided by abiding by easily managed limits. Remember that the recommended maximum PO 2 for recreational nitrox diving is 1.4 atmospheres, with a PO 2 of 1.6 atmospheres as a contingency amount. Plan your dives and choose a nitrox mix that is appropriate to the dive. Unit 4 - Choosing the Best Nitrox Mix Unit 4: Choosing the Best Nitrox Mix Enriched Air Nitrox Mixtures Calculating MOD Choosing your Best Mix Unit 4 - Choosing the Best Nitrox Mix Student Performance: By the end of the lesson you will be able to: Define Maximum Operating Depth and determine it for any nitrox mixture. Describe what Best Mix means and how to calculate it. Unit 4 - Choosing the Best Nitrox Mix Enriched Air Nitrox Mixtures Two Standard Nitrox Mixes EANx 32 or NOAA Nitrox I EANx 36 or NOAA Nitrox II Partial Pressure of Oxygen is the Limiting Factor Limit P0 2 to 1.4 ATA 1.6 ATA as a contingency Unit 4 - Choosing the Best Nitrox Mix Maximum Operating Depth The maximum operating depth (MOD) is the maximum depth that should be dived with a given nitrox mixture. MOD should be derived from the recommended maximum oxygen partial pressure of 1.4 atmospheres MOD should be written prominently on the cylinders contents label Unit 4 - Choosing the Best Nitrox Mix Maximum Operating Depth continued Calculating MOD Begin by finding the total pressure that it takes to produce the maximum acceptable oxygen partial pressure P g = F g x P total Then convert to a depth D fsw = (P ata 1 atm) x 33 fsw/atm Find the MOD for EAN36 (use 1.4 ata as O 2 partial pressure limit)? Unit 4 - Choosing the Best Nitrox Mix Maximum Operating Depth continued MOD by Table (imperial) Unit 4 - Choosing the Best Nitrox Mix Best Mix Best mix is the nitrox mixture with highest fraction or percentage of oxygen that can be used at the target depth. Unit 4 - Choosing the Best Nitrox Mix Choosing Best Mix continued Calculating best mix is similar to the calculation for maximum operating depth in reverse. Step 1: Determine the absolute pressure at the target depth or Unit 4 - Choosing the Best Nitrox Mix Choosing Best Mix continued Step 2: Determine what fraction will produce the target partial pressure at that absolute pressure Fg = Pg / P total or FO 2 = PO 2 / P total Unit 4 - Choosing the Best Nitrox Mix Choosing Best Mix continued For my thesis work dive surveys my maximum depth will be 120 as a contingency I am planning my maximum depth as 125. I want to find the EAN mix with the highest percentage of O2 that I can use for my survey dives. What is the EAN mix I should take with me??????????? My oxygen partial pressure limit is the AAUS standard. Pg = Fg x Ptotal Unit 4 - Choosing the Best Nitrox Mix Choosing Best Mix continued The Best Mix Table Unit 5 - Dive Tables and Dive Computers Unit 5: Dive Tables and Dive Computers Dive Tables Equivalent Air Depth and Standard Air Tables Using NAUIs RGBM Tables The Rule of Halves Dive Computers Unit 5 - Dive Tables and Dive Computers Student Performance: By the end of the lesson you will be able to: Demonstrate the use of NAUI EAN X Dive Tables. Define Equivalent Air Depth and how it is used with Air Dive Tables. Demonstrate how to determine and calculate Equivalent Air Depth. Demonstrate the use of the NAUI RGBM Nitrox Dive Tables. State the Rule of Halves and how to use it in all of your diving. Describe the procedures for using dive computers for EAN X diving. Unit 5 - Dive Tables and Dive Computers Dive Tables There are many different dive tables in use today NAUI Dive Tables NAUI RGBM Tables U.S. Navy Tables DCIEM Tables Buhlmann based tables Other Tables Unit 5 - Dive Tables and Dive Computers Air Dive Tables So-called standard dive tables are designed for diving while breathing air. Unit 5 - Dive Tables and Dive Computers No-required Stop Times EANx Dive Tables give increased maximum dive times for standard mixes. Unit 5 - Dive Tables and Dive Computers Enriched Air Nitrox Dive Tables Enriched Air Nitrox Tables Unit 5 - Dive Tables and Dive Computers Enriched Air Nitrox Dive Tables continued NAUI EAN Dive Table Rules Treat each dive as a square profile dive, with the deepest point reached on the dive being used as the depth for the whole dive. If the exact depth or time does not appear on the table, round up to the next greater number. The tables assume an ascent rate of 30 feet/9 meters per minute. Planning repetitive dives progressively shallower will yield shorter required surface interval times. The required surface interval between two separate dives is 10 minutes; the minimum recommended surface interval is one hour. The tables are designed to be used at sea-level atmospheric pressure, and adjustments must be made for altitudes above about 1000 feet/300 meters. If flying or ascending to altitude after diving, wait 12 hours after a single dive and 18 hours after a repetitive dive series. Unit 5 - Dive Tables and Dive Computers Equivalent Air Depth and Standard Air Tables Equivalent Air Depth is determined by the partial pressure of nitrogen that the diver is actually breathing Because nitrox has a lower fraction of nitrogen than air, the nitrogen partial pressure will also be less than with air for any given depth, and the divers equivalent depth for nitrogen absorption will also be less than with air. It is not the actual depth, but the partial pressure of nitrogen in the breathing gas that matters. Unit 5 - Dive Tables and Dive Computers Equivalent Air Depth and Standard Air Tables continued EAD Example: If you were breathing a mixture that is 36% oxygen, then the nitrogen percentage would be 64%, and the nitrogen fraction would be When you dive with this mixture, you expose yourself to 64/79ths the nitrogen partial pressure that you would encounter if breathing air. Therefore, you can consider your depth to be 64/79ths (roughly 80%) of the absolute pressure that you would encounter at your actual depth if you were breathing air. Unit 5 - Dive Tables and Dive Computers Equivalent Air Depth and Standard Air Tables continued Calculating Equivalent Air Depth Equivalent air depth can be calculated in discrete steps, or the procedure can be combined into a single formula. Step 1: Determine the absolute pressure at the depth to which you will be diving. Step 2: Apply the nitrogen credit that your nitrox blend gives you. Step 3: Convert this air-equivalent absolute pressure to an equivalent air depth Unit 5 - Dive Tables and Dive Computers Calculating EAD Example: What is the equivalent air depth for a diver diving with EAN 32 to a depth of 80 feet/24 meters? Equivalent Air Depth and Standard Air Tables continued Pg = Fg x Ptotal Step 1: Determine the absolute pressure at the depth to which you will be diving. Unit 5 - Dive Tables and Dive Computers Calculating EAD Step 2: Apply your nitrogen credit. Since you are diving with EAN 32, the nitrogen fraction of your mix is 0.68 (= ). Your air-equivalent absolute pressure is set by the ratio between the fraction of nitrogen in your mix and the fraction of nitrogen in air, or: Equivalent Air Depth and Standard Air Tables continued P ata (air equiv) = (0.68/0.79) x 3.42 ata = 2.94 ata Unit 5 - Dive Tables and Dive Computers Calculating EAD Step 3: Convert 2.94 ata to an equivalent air depth: D fsw = (P ata 1 atm) x 33 fsw / atm D fsw = (2.94 ata 1 atm) x 33 fsw / atm = 64 fsw You would use for 70 feet / 21 meters on your dive tables. Equivalent Air Depth and Standard Air Tables continued Unit 5 - Dive Tables and Dive Computers Equivalent Air Depth and Standard Air Tables continued Equivalent Air Depth by Table (imperial) Unit 5 - Dive Tables and Dive Computers Using NAUIs RGBM Tables NAUI RGBM Dive Tables are No- Calculation tables and do not require use of letter groups, a surface interval credit table, or residual nitrogen times, thus making repetitive dive planning extremely easy and straightforward. NAUI RGBM Dive Tables have been prepared for EAN 32 and EAN 36 as well as for air diving. The sea-level tables provide dive-planning information for altitudes up to 2000 feet/610 meters. Additional sets of tables are available for diving at altitudes between 2000 and 6000 feet/610 to 1829 meters and for 6000 and 10,000 feet/1829 to 3048 meters. Unit 5 - Dive Tables and Dive Computers Rule of Halves When ending any no-decompression dive in excess of 12 meters / 40 feet, halve the distance from the dives deepest depth to the surface. Ascend to that depth and make a one-minute safety stop. Then continue your ascent to the 5 meter/15 foot safety stop and complete the last two minutes of your three-minute safety stop at 5 meters/15 feet. Unit 5 - Dive Tables and Dive Computers Dive Computers and Nitrox Dive computers perform real time dive calculations. Generally, their algorithms are quite conservative. Because they sample the divers depth and dive time every few seconds and recalculate nitrogen absorption over a range of theoretical tissue compartments, divers enjoy extended dive times when using a dive computer. In effect, the diver receives credit for the shallow portions of the dive, which is not possible with the square-profile assumptions of dive tables. Unit 5 - Dive Tables and Dive Computers Dive Computers and Nitrox continued Two basic options Use a Nitrox capable computer Use an Air capable computer to increase your safety margins. Note: Currently, many manufacturers have incorporated the NAUI RGBM algorithms as well as the NAUI Rule of Halves into their dive computers. Unit 6 - Oxygen Precautions and Preparing Nitrox Unit 6: O 2 Precautions and Preparing EAN x O 2 Precautions The Fire Triangle 40% Rule Methods of Making Nitrox Unit 6 - Oxygen Precautions and Preparing Nitrox Student Performance: By the end of the lesson you will be able to: State the precautions that must be taken when around oxygen. Describe what the fire triangle is and how it applies to nitrox use. Describe oxygen cleaning is and what scuba equipment must be oxygen cleaned for nitrox use. Define the 40% Rule. Describe how cylinders and valves are prepared for nitrox use and how they are marked as nitrox cylinders. List five methods that are used to make nitrox and which are most common. Unit 6 - Oxygen Precautions and Preparing Nitrox Oxygen Handling Firefighters use the concept of the fire triangle. In order for a fire to occur or continue, three things must be present: fuel, oxygen, and heat. As the fraction and partial pressure of oxygen increase, many materials that do not burn under normal conditions will burn if ignited. Unit 6 - Oxygen Precautions and Preparing Nitrox Oxygen Handling continued Equipment that will be used with pure or very high concentrations of oxygen must be specially prepared to withstand the oxygen and to prevent fires and oxidation. GENRAL RULE IS ANYTHING OVER 40% NEEDS SPECIAL PREPARATION Unit 6 - Oxygen Precautions and Preparing Nitrox Oxygen Handling continued The 40% Rule Any equipment that is to be used with pure oxygen or an oxygen level that is above 40% (and at a pressure above 200 psi) must be cleaned for oxygen service and have only oxygen-compatible parts. This is a rule of thumb, but it is generally accepted for oxygen handling. Unit 6 - Oxygen Precautions and Preparing Nitrox Oxygen Handling continued Equipment Considerations Hydrocarbons and petroleum-based products must be avoided FOR ALL MIXES. This includes not only petroleum-based compressor lubricants but also the silicone lubricants normally used in scuba air systems. Neoprene, silicone rubber, plastic and metal shavings, even finely divided particulate matter all become potential fuels for a fire in an oxygen-rich environment, especially one at high pressure. Unit 6 - Oxygen Precautions and Preparing Nitrox Oxygen Handling continued Oxygen Cleaning (>40% mixes) The equipment must be oxygen clean, and oxygen compatible parts must be used in order to minimize the risk of fire or destruction by the oxygen. After cleaning, future contamination must be avoided. Unit 6 - Oxygen Precautions and Preparing Nitrox Oxygen Handling continued Equipment Preparation Normal maintenance service is sufficient for your regulator. Your cylinder is a different matter. Unit 6 - Oxygen Precautions and Preparing Nitrox Oxygen Handling continued Equipment Preparation continued Cylinders must be prepared for designated nitrox service because most of the time pure oxygen will be used in preparing a nitrox fill. After being cleaned for use with oxygen-enriched air, the cylinder will be labeled to clearly identify it as a nitrox cylinder. Unit 6 - Oxygen Precautions and Preparing Nitrox How Nitrox is Made Partial-Pressure Mixing(MLML) In partial-pressure mixing, the blending technician first puts a measured amount (pressure) of oxygen into the cylinder and then fills the cylinder to its service pressure with air. Unit 6 - Oxygen Precautions and Preparing Nitrox How Nitrox is Made continued Continuous-Flow Mixing The continuous-flow method injects a measured flow of pure oxygen into the air before it reaches the intake of the compressor Unit 6 - Oxygen Precautions and Preparing Nitrox How Nitrox is Made continued Pressure Swing Absorption This method removes nitrogen from air rather than adding oxygen to it. PSA passes air alternately over a molecular seive that adsorbs nitrogen. Unit 6 - Oxygen Precautions and Preparing Nitrox How Nitrox is Made continued Membrane Separation Membrane separation uses a semi-permeable membrane that allows oxygen to flow through it more readily than nitrogen. Unit 6 - Oxygen Precautions and Preparing Nitrox Your Responsibility As a nitrox diver, you are responsible not only for your dive planning and execution but also for your equipment. You are also responsible for the correctness of what you will breathe. You are responsible for your cylinders contents being what you asked for. A final step before you take the cylinder away with you is verifying the contents. Unit 7 - Knowing What You Breathe Unit 7: Knowing What You Breathe Oxygen Analyzers Analyzing Your Gas Cylinder Labeling Filling Out The Logbook Unit 7 - Knowing What You Breathe Student Performance By the end of this lesson, you will be able to: Describe oxygen analyzers and why analysis is necessary. State how to analyze your nitrox list. Describe how your cylinder should be labeled after it is filled. Explain why a fill station logbook is kept and how to enter your fill information in the log. Unit 7 - Knowing What You Breathe How Oxygen Analyzers Work Oxygen analyzers come in all sizes Most have digital readouts, but analog readouts are also available Analyzers should have an accuracy of one-tenth of one percent (e.g., 31.7% vs. 32%) Unit 7 - Knowing What You Breathe How Oxygen Analyzers Work continued The sensor commonly used in nitrox analysis is electrochemical They are rugged, portable and relatively less expensive than other types An essential operation in using any analyzer is calibrating it Must be calibrated before each use Nitrox analyzers are normally calibrated using standard air (20.9% or 21%) Generally accepted that mix be within 1% of target value Unit 7 - Knowing What You Breathe Analyzing Your Gas Accurate analysis depends on the reliability of the analyzer and the flow rate through the oxygen sensor. Acceptable flow rate is about 1 liter per minute and should be between and 2 liters per minute. Unit 7 - Knowing What You Breathe Analyzing Your Gas continued Accurate oxygen analysis depends on accurate calibration of the analyzer. Use a known source such as an air cylinder to ensure proper calibration. Once calibrated, attach the analyzer to your nitrox cylinder, confirm that flow rate is the same as during calibration and allow analyzer to stabilize. Record this information on your cylinder contents label. Unit 7 - Knowing What You Breathe Tracking Your Nitrox Cylinder Cylinder Labeling Every nitrox cylinder must be properly labeled with contents and other pertinent information. Prepare cylinder label immediately after analyzing to avoid forgetful errors. Data should include fill date, oxygen percentage, maximum operating depth, cylinder pressure, and name of analyzer/end-user. Unit 7 - Knowing What You Breathe Tracking Your Nitrox Cylinder continued Filling Out The Logbook Once you have analyzed your cylinder and labeled it, you will be asked to complete the permanent Fill Station Logbook and sign that you have received the cylinder. Enter your name, date, your certification, cylinders serial number, pressure, oxygen mix, maximum operating depth, signature. Logbook tracks all nitrox cylinders leaving facility. Logbook verifies that you either analyzed the contents or knew the particulars of the fill when you received your cylinder.