1 / 71

Nitrox

Nitrox. Course Overview. This is not a basic scuba class and it will not be taught as such. You should already have the skills and knowledge to dive safely and with common sense.

kellan
Download Presentation

Nitrox

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nitrox

  2. Course Overview • This is not a basic scuba class and it will not be taught as such. • You should already have the skills and knowledge to dive safely and with common sense. • However because we have divers at different levels of skill, experience, and knowledge we will review some basic academic areas such as gas laws, dive tables and decompression theory. • This is a BASIC NITROXCOURSE and we will limit our discussions to BASIC NITROX USE.

  3. Qualifications of Graduates • Competent to utilize EANx in open water diving activities without direct supervision. • Obtain EANx cylinder refills with a maximum percentage of Oxygen of 40%.

  4. Objectives • Identify the agency through which your certification will be issued. • Identify the maximum percentage of oxygen you will be certified to use. • Identify the maximum depth to which you will be certified to dive. • Describe the concept of Partial Pressure (Dalton’s Law) as it applies to Nitrox. • Describe the benefits and risks of using Nitrox on scuba. • Describe the benefits and risks of using air on scuba. • Identify the recommendations for P02 exposures for • Maximum scuba limit for recreational/low exertion dives. • Bottom times over 45 minutes. • Particularly hard dives. (This limit applies to all dives in Monterey.) • Discuss concerns for applying P02 limits to any individual. • Describe two factors associated with causing CNS Oxygen toxicity. • Identify signs and symptoms of CNS Oxygen toxicity, and discuss procedures to minimize the risk of CNS 02 toxicity.

  5. Objectives cont. • Convert pressure in atmospheres absolute (ata) to depth. • Convert depth to pressure in atmospheres absolute (ata). • Calculate Maximum 02 dose when given F02 and Pressure (depth). • Calculate Maximum depth when given P02 and F02. • Calculate the best mix to use when given P02 and Pressure (depth). • Describe Equivalent Air Depth (EAD) Theory. • Determine appropriate EAD using either the EAD formulas or the EAD Table. • Calculate P02 and single limit exposures using the TDI chart. • Using the appropriate P02 and EAD charts as well as the NAUI dive tables, correctly plan and calculate end of dive letter groups for dives using various Nitrox mixes. • Discuss equipment issues and concerns and describe appropriate markings for scuba cylinders used for Nitrox. • Discuss the 40% rule as it applies to Nitrox. • Discuss and compare various methods of making Nitrox.

  6. Terminology • NOAA NITROX I 32% 02 68% N2 • NOAA NITROX II 36% 02 64% N2 • GOD’S NITROX 21% 02 79% N2 • Other terms you will hear include: • Enriched Air • Enriched Air Nitrox (EANx) (x = %02 in mix) • Safe Air • Normoxic

  7. History of Nitrox • First documented use 1879 • U.S. Military published NITROX tables 1950s • NOAA published NOAA NITROX tables • NOAA Nitrox 1 1979 • NOAA Nitrox II 1991 • NOAA PUBLISHED equivalent air depth (EAD) tables • Technique for diving NITROX while using air tables • First recreational Nitrox agency established1988 • NAUI Sanctions teaching Nitrox 1992 • Credit for developing and introducing Nitrox diving techniques goes to Dr. Morgan Wells

  8. NOAA/NATIONAL UNDERSEA RESEARCH PROGRAM • 1988Workshop on Enriched Air Nitrox Diving • Concluded the approaches to use of Nitrox were sound • Basically endorsed the use of Oxygen enriched air • Settled on the term Enriched Air Nitrox EANx DAN/Dr Peter Bennett: • Technical diving with Nitrox is not in the category of recreational diving for the diver whose training is limited and whose goal is fun. • “...should be left to the organizations with appropriate specialized equipment, training, and control.” EVALUATING ENRICHED AIR (“NITROX”) DIVING TECHNOLOGY • 1992 symposium sponsored by Scuba Diving Resource Group • Conclusions: • Basic NITROX is not technical diving. • Basic NITROX does not require a great deal of special training. • For most recreational divers, the understanding of basic physics and physiology is generally weak.

  9. NITROX Misconceptions • Deep Diving • Extensive Course • Expensive Course • Expensive Gear • Cave or Technical Diver • Recreational Divers not smart enough • Recreational Divers not safe enough

  10. NITROX Realities • Most dives shallower than 130” therefore not technical diving • 4 hour course • some formulas • use of tables • Doesn’t require new gear • Perform same underwater activities • Safety proven since 1985 • Sport divers are smart enough

  11. Air vs. EANx Air • A mixed gas consisting of 21% 02 79% N2 Advantages of Air compared to EANX • Cheap (maybe) • Easily available • You can dive it right now • Depth Disadvantages of Air compared to Enriched Air Nitrox • Narcosis (maybe!) • DCS • Fatigue (Maybe!)

  12. Air vs. EANx cont. • NITROX • A mixed gas consisting of any combination of 02 &N2. • Advantages of EANX compared to Air • More bottom time or shorter Surface Interval • N2 is still the limiting factor • Safety factor using air tables/computers • Decreased risk of narcosis (not documented) • O2 may contribute to narcosis • Decreased post dive fatigue (not documented) • Improved gas consumption (not documented) • Warmth (not documented)

  13. Advantages of EANX compared to Air cont. • Less risk of DCS • Risk factors of DCS • older age • obesity • dehydration • poor circulation • illness • scar tissue • alcohol • fatigue • strenuous exercise • cold • repetitive dives • multi day diving • history of DCS

  14. Disadvantages of EANx compared to air • Shallower 02 toxicity concern • Using 1.4 atm • air 187 fsw • NNI 111 fsw • NNII 95 fsw • CNS 02 Toxicity can be confused with N2 Narcosis but 02 Toxicity more serious

  15. Physiology • Body is concerned with • P02 and • Exposure time • Recommended max exposure limit • 1.6 ata maximum exposure • 1.4 ata recreational,cold or working dive • O2 tolerance limits vary from individual to individual and from day to day • No good test available

  16. Depth and Pressure Review • Depth = Actual depth underwater • Pressure atmospheres in Seawater • (Depth +33)/33 or • (Depth/33) + 1 • Pressure atmospheres in fresh water • (Depth +34)/34 or • (Depth/34) +1

  17. Review Dalton’s Law • P=Pg1+Pg2+Pg3 etc. • P=absolute pressure • Pg=partial pressure of gas • Dalton’s Law for Air at sea level • P = P02 + PN2 • 1.0 ata = .21 ata + .79 ata • Dalton’s Law for Nitrox: • P = P02 + PN2 • Dalton’s Law for NNI at sea level • 1.0 ata = .32 ata + .68 ata • Dalton’s Law for NNII at sea level • 1.0 ata = .36 ata + .62 ata

  18. Determining the Partial Pressure of a Gas 2 Step Process • Step 1 P total = (Dfsw/33 fsw/atm) + 1 atm • Step 2 P02 = F02 x P total

  19. Determining the Partial Pressure of a Gas What is the P02 of EAN 38 at 112 fsw? • Step 1 P total = (Dfsw/33 fsw/atm) + 1 atm P total = (112 fsw/33 fsw/atm) + 1atm = 4.4 atm • Step 2 P02 = F02 x P total P02 = .38 x 4.4 atm = 1.67 atm

  20. Dalton’s Law cont. • Partial pressure can also be used to determine the percentage or fraction of a component gas. • Pg/P = Fg • P02 / P = F02 • .21 ata / 1.0 ata = .21 • PN2 / P = FN2 • .79 ata / 1.0 ata = .79

  21. Determining the Percentage or Fraction of a Gas 2 Step Process • Step 1 P total = (D fsw/33 fsw/atm) + 1 atm • Step 2 F02 = P02/P total

  22. Determining the Percentage or Fraction of a Gas • If the P02 of your Nitrox mix is 1.2 atm at 122 fsw, what is the F02 of the mix? • Step 1 P total = (D fsw/33 fsw/atm) + 1 atm P total = (122 fsw/33fsw/atm) + 1 atm • Step 2 F02 = P02/P total F02 = 1.2 atm/4.7 atm =0.255 = 25.5%02

  23. Dalton’s Law cont. • Remember that the fraction of a gas delivered during a dive is constant. However the partial pressure changes with depth.

  24. EQUIVALENT AIR DEPTH THEORY • During a NITROX dive less N2 will be absorbed than on an air dive of same depth and duration. Don’t forget you will be exposed to a higher partial pressure of oxygen. • EAD is a technique whereby you calculate the N2 partial pressure for your mix and use the air table depth that has the same partial pressure.

  25. Equivalent Air Depth • Formula EAD fsw =[ (FN2ean x Dfsw+33fsw/atm) – 1atm] x 33fsw/atm FN2 air 33fsw/atm Or Use a table

  26. Oxygen Physiology Concerns • O2 used can be aviation or medical • Individual tolerance to 02 varies from person to person. • Individual tolerance to 02 varies from day to day.

  27. Oxygen Physiology Concerns • O2 tolerance is decreased by CO2 • C02 is the primary waste product from the metabolism of 02. • C02 retention which can be caused by • Poorly functioning regulator • Inefficient breathing • Labored breathing (hard work) • Heavy exercise

  28. Oxygen Physiology Concerns • 02 Exposure limits assume: • Low/moderate exercise • No breathing restriction • No excess C02 (snorkel) • No unusual 02 exposure prior to the dive

  29. Oxygen Toxicity CNS 02 Toxicity • Caused by short term exposure to high P02 • P02 levels below 1.5 ata are unlikely to cause CNS toxicity no matter what the duration of exposure. • Maximum recommended P02 for recreational diving of EANx = 1.4 ata

  30. CNS 02 Toxicity • CONvulsions • Visual symptoms • Eurphoria/Ears • Nausea • Twitching (lips, cheeks, nose, diaphragm) • Irritability • Dizziness Warning signs vary greatly and sometimes do not occur at all.

  31. CNS 02 Toxicity Emergency Techniques • Ascend immediately • Switch to air immediately • Have a hang tank or bailout bottle of Air. • On deep dives be aware of the danger of N2 Narcosis

  32. Pulmonary/Whole Body 02 Toxicity • Caused by long term exposure to P02 over .5 ata. • Not very likely in recreational diving

  33. Pulmonary/Whole Body 02 Toxicity Signs • Soreness in chest and airway • Dry cough • Head ache • Fatigue • Loss of aerobic capacity • Numb fingertips • Parestheses • Aches and pains • Vital capacity decreased • If not caught soon enough = may be chronic

  34. Pulmonary/Whole Body 02 Toxicity The effects of Pulmonary/Whole Body 02 Toxicity typically are relieved when the P02 drops below .5 ata.

  35. To avoid problems with 02 Toxicity • Always analyze the gas • Too much 02 = less depth • Too little 02 = less time • Do not exceed the time and depth limits for your gas mix. • Biggest risk is not knowing what you are diving

  36. Other Concerns • DCS • You can get bent while using Nitrox • If diving within the recreational limits the treatment will be as if you were on air • Narcosis • You can get narcosis while diving Nitrox • Nitrogen is inert gas so our bodies do no use the N2 in the gas we breathe acts similar to anesthia • 02 may contribute to narcosis • Treatment is to ascend

  37. Hypoxia (Low 02 levels) • Onset of symptoms • PO2 .14-.16 ata • More severe symptoms • P02 .09-.10 ata • Unconscious for most people • P02 .08-.10 ata • Coma-death • P02 <.08 ata

  38. Hypoxia Signs/Symptoms • Euphoria • Itching/tingling • Tunnel vision • Impaired mental performance • Defective memory • Cyanosis • Fatigue • Visual disturbances • Dizziness

  39. Dive Planning • Maximum Operating Depth (MOD) • The maximum depth a particular gas can be used without exceeding an oxygen toxicity limit, based on the partial pressure of the oxygen at depth. • NAUI P02 =1.4 ata • Factors • Percentage of 02 • Depth

  40. Calculating MOD 2 step process • Step 1 • Pata = P02 limit/F02 • Step 2 • Dfsw = (Pata – 1 atm) x 33 fsw/atm

  41. Calculating MOD • What is the maximum operating depth (MOD) for air using 1.4 ata? • Step 1 P ata = 1.4 atm/.21 = 6.67 atm • Step 2 Dfsw = (Pata – 1 atm) x 33 fsw/atm Dfsw = (6.67 atm -1 atm) x 33 fsw/atm Dfsw = 187 fsw

More Related