Unformatted text preview: Tonight’s Topics
Tonight’s Topics Temperature and diving More diving equipment
Indirect effects of pressure The gasses we breathe
Using Dive tables This week in the pool Note Quiz 1 (NAUI Scuba Diver) on October 19 Thermal Effects of Diving
Thermal Effects of Diving You lose heat underwater in several ways. Water conducts heat away from you body rapidly. (25 times faster than air)
Breathing cold compressed air from a cylinder. You must warm and humidify the air before it reaches your lungs Humidity and temperature: Condensation on your mask Temperature and Pressure
Temperature and Pressure The pressure in your cylinder will increase or decrease as the temperature increases or decreases
Cylinders should be kept from extreme heat after they are filled. Review on Thermal Effects
Review on Thermal Effects
What have you learned so far? Name two primary ways of losing heat while on scuba.
Describe what happens to the pressure in a scuba cylinder if the temperature is increased. Diving Suits
sDifferent ranges of temperature feel comfortable to different divers. Diveskins: Tropical waters. Protective covering to avoid injuries and sunburn. Most common types: Lyrca and Polartec.
Wetsuits: Made from foam neoprene: Must fit precisely and snugly. Water that is trapped in the suit helps keep you warm. Available in 2mm to 7mm thickness and many styles:
Dry suit: Worn with undergarments for warmth Diving Suits: Choosing the right suit
Diving Suits: Guidelines for deciding what type of diving suit to wear:
28° C (82° F) and warmer water Diveskin
23° C to 30° C (75° F to 85° F) waters 2 to 3mm full wetsuit or shorty
13° C to 27° C (55° F to 80° F) waters 5 to 7mm full wetsuit
2° C to 16° C (35° F to 60° F) waters Full drysuit 2° C (35° F) and colder waters Special training and equipment are needed Diving Suits: Maintenance
Diving Suits: Maintenance includes: Rinse diveskins and wetsuits inside and out. Commercial products are available to help clean your suits completely before storage. Hang wetsuits on wide hangers to prevent creases. Review on Diving Suits
Review on Diving Suits
What have you learned so far? Which suit would you choose for warm, tropical diving? Which suit is made from neoprene rubber? Which suit uses an undergarment? Accessory Equipment
Accessory Equipment Some useful accessories are: Clips to attach your instruments etc.
A dive knife is a working tool used for many purposes.
A gear bag to transport your gear.
Diverdown flag lets others know you are underwater. Laws vary.
A logbook is your record of experience in the water and your level of training.
It is a good idea to have a first aid kit on any dive trip. Accessory Equipment
Accessory Equipment Some more useful accessories are: Underwater slate.
Marker buoy and line.
Spare parts kit.
Checklist. Review on Accessories
Review on Accessories
What have you learned so far? What is the most likely use for a knife underwater?
What must you do when you fly a dive flag?
What are two reasons for logging your dives in a logbook?
Name two additional accessories that are useful when diving? The Air You Breathe
The Air You Breathe Scuba cylinders are normally
filled with dry, filtered air.
Air is a mixture of gases.
As pressure increases underwater, the increased pressure of each of the gases in the air we breathe has physiological effects. Henry’s Law
Henry’s Law (Solubility of gases) Henry’s Law: The amount of gas that will dissolve in a liquid is directly proportional to the pressure of the gas.
Gases go into and come out of solution in our body as the pressure of the gas changes. When we dive, we “ingas”; then when we surface, we “offgas.” Dalton’s Law
Dalton’s Law (Partial pressures) Dalton’s Law: The total pressure exerted by a mixture of gases is equal to the sum of the pressures of each gas.
The pressure of each component gas is called its “partial pressure.” Our body “feels” each gas individually. Carbon Dioxide Problems
Carbon Dioxide Problems Carbon dioxide controls the need to breathe. Shallow water blackout: When freediving, hyperventilating before the dive purges carbon dioxide from our body and delays the stimulus to breathe.
Excessive hyperventilation can allow us to use up our oxygen before we know we have to breathe.
Shallow water blackout is easy to prevent: Hyperventilating on scuba (stress or exertion): Skip breathing on scuba: Carbon Monoxide & Carbon Monoxide & Contaminated Air Carbon monoxide bonds to hemoglobin more strongly than oxygen.
CO levels in pure air are not a problem.
Breathing air underwater that is contaminated with CO can be a problem
(partial pressure increases with depth). Smoking tobacco greatly increases CO levels. Signs/symptoms/first aid. What to do if you suspect that you air is bad. Oxygen Toxicity
Oxygen Toxicity Oxygen can be poisonous at high concentrations.
As the partial pressure of oxygen gets above 1.4 to 1.6 atmospheres, oxygen can become toxic.
It is not a problem when diving to normal depths and breathing air.
Nitrox divers must be aware of the oxygen partial pressure in their breathing gas.
Signs/symptoms/treatment/prevention. Nitrogen Narcosis
Nitrogen Narcosis Breathing nitrogen under pressure can produce a narcotic effect (“rapture of the deep” Cousteau). Depth of onset varies. Other factors contribute. Susceptibility and effects vary. Signs/symptoms. Dealing with nitrogen narcosis. Nitrogen and “the Bends”
Nitrogen and “the Bends” The nitrogen that dissolves in your tissues during a dive is the gas you are concerned about when planning your dives.
Decompression Sickness: Residual Nitrogen
Residual Nitrogen Residual nitrogen is the excess nitrogen that is in your body after a dive.
Residual nitrogen reduces your maximum dive time for any given depth on your next dive. Think of residual nitrogen as a partially paiddown credit card. Decompression Sickness
Decompression Sickness Caused by staying too deep for too long and coming up too fast
It takes time for nitrogen to enter and to leave the body.
If to much nitrogen is absorbed, it cannot be breathed out normally. Bubbles form in body tissues. Signs/symptoms: Depend on bubble site. Contributing factors: Preventing
Decompression Sickness Avoid dives that are too deep, too long, and/or too fast an ascent.
Dive tables and dive computers allow us to monitor nitrogen levels in our body for a dive or a series of dives. Follow table rules. Keep well hydrated. Treating
Decompression Sickness First aid includes breathing 100% oxygen. Treatment is in a recompression chamber. The chamber is pressurized to force the nitrogen bubbles to go back into solution. Then the pressure is slowly released. Dive Table Overview
Dive Table Overview The NAUI Dive Tables monitor the nitrogen in your body
They use the letters of the alphabet to express the extra amount of nitrogen in your body.
The letters range from A to L. Dive Table Terms
Dive Table Terms The following terms apply to the NAUI Dive Tables: Depth. Actual Dive Time (ADT). Dive schedule (depth/time). Maximum Dive Time (MDT). Letter Group Safety stop. Decompression Stop. Dive Table Terms (continued)
Dive Table Terms Residual nitrogen.
Letter Group designation.
Surface Interval Time (SIT).
Residual Nitrogen Time (RNT).
Adjusted Maximum Dive Time (AMDT).
Total Nitrogen Time (TNT). Dive Table Rules
Dive Table Rules Use the deepest depth you reach during your dive. Do not try to average your depths. Use exact or next greater number for your depth.
Use exact or next greater number for your time.
Maximum ascent rate is 30 feet (9 meters) per minute. Dive Table Rules (continued)
Dive Table Rules A “safety stop” is recommended at the end of each dive.
Make your deepest dive first.
Dives shallower than 40 feet (12 meters) are planned as 40 feet (12 meters). Dive Table Rules (continued)
Dive Table Rules SIT must be at least 10 minutes to count as a second dive.
Recommended SIT is 60 minutes.
Use the next greater dive time if dive was cold or strenuous. Review on Dive Table Rules
Review on Dive Table Rules
What have you learned so far? What is the maximum ascent rate according to NAUI dive tables?
What is the minimum amount of time needed between two dives and the recommended amount of time?
In what order should dives be made according to depth? Dive Table Organization
Dive Table Organization
The NAUI dive tables are composed of three tables. Table 1: EndofDive Letter Group. Examples: Dive Table Organization
Dive Table Organization
The NAUI dive tables are composed of three tables. Table 2: Surface Interval Time (SIT) Table. Examples: Dive Table Organization
Dive Table Organization
The NAUI dive tables are composed of three tables. Table 3: Repetitive Dive Timetable. Examples: Dive Planning Worksheet
Dive Planning Worksheet It helps to use a worksheet to record information when using Dive Tables. Planning your dive.
Finding your letter group.
Recording your SIT and finding your new group letter.
Planning your repetitive dive.
Recording your repetitive dive. Using Dive Tables Using Dive Tables What is the diver’s ending letter group?
Dive 1: Max. Depth: 66 feet (20 meters)
ADT: 36 minutes.
SIT: 1 hour 50 minutes.
Dive 2: Max. Depth: 46 feet (14 meters) ADT: 32 minutes.
SIT: 1 hour 35 minutes.
Dive 3: Max. Depth: 40 feet (12 meters)
ADT: 43 minutes.
66 fsw 1:50 E I
46 fsw 1:35 F J
40 fsw 0
36 min. 38 min.
32 min. 61 min.
43 min. 36 min. 70 min. 104 min. Maximizing Underwater Time
Maximizing Underwater Time You can maximize your dive by: Planning your surface interval “Deeper dive first” means less required surface interval Limiting your depth Limiting your dive time Find the minimum surface interval
Find the minimum surface interval Dive 1: 80 feet (24 meters)
ADT: 25 minutes
Dive 2: 60 feet (18 meters)
ADT: 25 minutes
What is the minimum required surface interval time?
What is the recommended SIT?
80 fsw 0:46 E I
60 fsw 0
25 min. 30 min.
25 min. 25 min. 55 min. Special Rules
Special Rules There are a few special procedures to handle special situations. Decompression diving. Planned decompression diving is an advanced level skill. Recreational divers should avoid deco dives. Omitted decompression.
Cold or strenuous dives.
Flying after diving.
Altitude diving. Dive Computers
Dive Computers The easiest way to determine how long you can dive is to use a dive computer. Remember: Both dive tables and dive computers use theoretical models. You, however, are a carbon
based life form. Tables and computers don’t get bent—Divers get bent.
The great advantage of a computer is extended dive times.
A dive computer continually samples time and depth (pressure) and recalculates your nitrogen loading
So, a computer gives you “credit” for the shallow parts of your dive.
No “square profile” as tables require. Dive Computers
Dive Computers Displayed information Initialization
Planning repetitive dives Current depth
Current dive time
Time remaining at depth
Ascent rate indicator Scrolling or dive planning Altitude diving
Flying after diving indicator
Logging your dives Downloading to a computer logbook Dive Computers
Whoops! A dive computer is an electronic device and can fail. What if the screen goes blank?
We hope you’ve been checking your display regularly!
End the dive normally.
Follow the manufacturer’s recommendations. Review of Decompression
Review of Decompression Nitrogen and Diving.
Dive Table Overview.
Dive Table Organization.
Dive Planning Worksheet.
Maximizing Your Underwater Time.
Using Dive Computers. This Week in the Pool Normal lab times apply from now on.
Don’t gforget to sign in.
“If you don’t sign in, you are not there.”
Be on time. When you arrive at the pool:
When you arrive at the pool: Sign in on the roster. Get your equipment from the Dive Locker Scuba gear: BC, regulator, cylinder Mask/snorkel and fins
Wetsuit, belt, two weights Begin assembling scuba unit. We’ll monitor your assembly. ...
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- Fall '10
- Decompression sickness, Dive Computers, Dive Table