Scuba Review
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- When diving in tropical waters, what potential danger is often ignored to the divers regret?
- Sunburn
- Name 5 non-aggressive, but potentially harmful, sea creatures.
- Shark, moray eel, sting ray, sea urchin, fire coral, portuguese man-o-war, jelly fish, octopus, barracuda
- Give 3 water conditions that would prohibit ocean diving.
- Current, tides, visibility, wave, surf, pollution.
- Why does the moray eel pose a particular threat to divers gathering lobsters?
- The eel and the lobster live in the same holes and crevices. A diver may reach into one of these holes while seeking a lobster and get bit by the eel.
- When diving in tropical waters, what procedures would you use to avoid stings and injury from a Portuguese Man-O-War or a jelly fish?
- By using your octopus and "blowing" them away. Look up and circle 360 degrees as you ascend to the surface
- How would you recognize fire coral and why would you want to avoid it?
- Mustard yellow with white tips. Takes on form of various corals, has many stinging cells.
- What are 2 ways to avoid injury from a sting ray?
- 1)Shuffle feet in water when entering a beach area. 2) Do not swim close to bottom.
- Explain the proper procedure to follow if caught in a "rip-current".
- Inflate your B.C. and ride with the current If possible, swim perpendicular to current until our of it.
- What is the danger of touching a stone fish/ scorpion fish?
- Their defense is being able to blend into the bottom. Their dorsal spines contain a toxin which can be fatal to humans.
- Why would a diver want to make a night dive?
- Different forms of life come out to feed, opportunity to see nocturnal animals..
- Air is a mixture of several gases. State the two main components and their relative percentages of the mixture.
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Oxygen: 20%
Nitrogen: 80% - What is the pressure increase per foot of depth, in psi for: 1)Salt water 2)Fresh Water
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S.W. .445 psi/ft
F.W. .432 psi/ft - One half cubic foot of salt water displaced will give a buoyant force of how many pounds? What law is this related to?
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(64 lbs/ft cu.)x(.5 ft cu.) = 32 lbs
Related to Archimedes Principle - One half cubic foot of fresh water displaced will give a buoyant force of how many pounds?
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(62.4 lbs/ft cu)x(.5 ft cu.) = 31.2 lbs
Archimedes Principle - What is Boyle's Law?
- Pressure and Volume are inversely related. As pressure increases, volume decreases, and vice versa...
- The pressure at sea level is equal to what? (in psi and in atm)
- 14.7 psi which equals 1 atm
- Describe the difference between absolute pressure and gauge pressure.
- Gauge pressure tells the pressure of the surrounding water, absolute pressure includes the 1 atm of pressure from the above air.
- What is the #1 rule of scuba diving?
- Never Hold Your Breath!
- State Henry's Law.
- The solubility of a gas in a liquid is almost proportional to the partial pressure of that gas.
- How does Henry's Law relate to scuba diving?
- At increased depth (and pressure), more Nitrogen from the air goes into solution in the diver's body tissues.
- A diver fills his balloon with air from his tank at a depth of 66ft(salt water). What will the volume be when brought to the surface?
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V2=(D1+33)xV1/(D2+33)
V2=(66+33)x 2/(0+33)
V2=99 x 2 / 33
V2=6 ft cu. (1/3 the pressure, 3x the volume) - A diver fills his tank to 3 cubic ft of air in his tank at 99 ft of fresh water. What will the volume be when brought to the surface?
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V2=(D1+34)xV1/(D2+34)
V2=(99+34)x 3/(0+34)
V2=133 x 3 / 34
V2= approx 12 ft cu.(1/4 the pressure, 4x the volume) - What 2 problems can Nitrogen cause when scuba diving?
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1) Nitrogen Narcosis
2) Decompression Sickness (the Bends) - What is the sequence of colors to be filtered out as you descend?
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ROY G BIV
(red, orange, yellow, green, blue, indigo, violet) - Why will a diver become chilled in 80 degree water?
- Water transfers heat away 25x faster than air. 80 degrees is 18 degrees cooler than our body temp (98.6)
- How much larger and closer to objects appear in water?
- 1/3 (33%) larger, and 25% closer.
- Does sound travel faster in air or water? How does it affect a diver?
- Travels 4x faster in water. Makes it difficult to distinguish what direction sounds are coming from.
- What is the absolute pressure, in psi, at 100 ft of salt water?
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P=(D+33)x.445
P=(100+33)x.445
P=133x.445
P=59.2 psi - What is the absolute pressure, in psi, at 66 ft of fresh water?
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P=(D+34)x.432
P=(66+34)x.432
P=100x.432
P=43.2 psi - What are alveoli and what are their function?
- Alveoli are the small sacs found in the lungs where gasses are exchanged between the inhaled air in the sacs and the capillaries surrounding the sacs.
- When diving, what is the pressure of the air we breathe from the regulator?
- The regulator delivers air to the diver at the ambient water pressure.
- What is the function of the Eustachian tube, and why do divers care about it?
- It connects the middle ear cavity to the back of the throat. It maintains pressure between the out and middle ear which are separated by the ear drum.
- What is squeeze?
- The affect of unequalized pressure on any of the body's internal or attached crevices.
- What are some examples of parts affected by "squeeze"?
- Ear, sinus, thoracic, tooth, intestinal, mask, hood, and suit squeeze.
- Will a tank of air last longer at a depth of 30ft or 90ft? Why?
- 30 ft. It takes almost twice as many air molecules to fill your lungs at 90 ft as at 30 ft. (Boyle's Law)
- What is the danger of diving with a head cold?
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1) Sinus squeeze
2) Ruptured ear drum - What is the danger of taking decongestants before a dive?
- If the decongestant wears off during the dive, you may encounter reverse squeeze, and may not be able to clear ears and/or sinuses on ascent.
- Describe two possible ways of rupturing an ear drum.
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1) Not clearing the ears during descent.
2) Hood squeeze - How does a diver avoid mask squeeze?
- Exhale into mask during the descent in order to equalize pressure between inside of mask and surrounding water.
- What should a diver do when he/she encounters ear or sinus squeeze?
- Ascend until symptoms disappear, if ears or sinuses don't clear after several attempts to descend, abort dive.
- What is the Valsalva Maneuver?
- Pinch nose and exhale in order to equalize pressure in ears.
- What is the Toynbee Maneuver?
- Pinch nose, close mouth and swallow to equalize pressure in ears.
- What do you experience when an ear drum blows?
- Causes vertigo: disorientation, loss of balance
- At 130ft your buddy starts acting funny: a) what do you do? b) what is the name of this problem? c) what is the cause of this problem?
- a) Get your buddy to ascend 20-30 ft or until he behaves normally. b) Nitrogen Narcosis. c) Breathing nitrogen at a high partial pressure.
- Name 2 ways a scuba diver can incure Oxygen poisoning.
- (occurs when breathing Oxygen at a partial pressure above 1.5 atm) 1) compressed air below 218ft. 2) Nitrox below recommended depth 3) oxygen rebreather below 33ft
- What is the primary sign of Oxygen poisoning?
- Convulsions
- What is the danger facing a skin diver who hyperventilates excessively before a deep dive?
- Shallow Water Blackout
- During a dive, you are working hard and begin to feel anxious and out of breath, a) what do you do, b) What do you think the problem is?
- a) slow down and catch your breath. b) carbon dioxide buildup.
- When breathing from a new tank, the air has a burnt or oily taste, a) what is the risk of using the tank? b) what could cause this strange taste?
- a) carbon monoxide buildup b) dieseling in the compressor, or air inlet to compressor is too close to a source of engine exhaust
- What is hypoclycemia? How can it be prevented?
- Hypoglycemia is low blood sugar. In scuba, usually result of poor diet. To avoie eat healthy meals before diving.
- Descibe symptoms of vertigo and give to possible causes.
- Symptoms include spatial disorientation, dizziness, and nausea. Caused by ruptured ear drum, lack of visual reference, and ascent vertigo.
- A skin diver fills his lungs to 10 pints, then dives down to 20 ft in the ocean, what is the volume of air in his lungs at 20 ft?
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V2=((D1+33)xV1)/(D2+33)
V2=((0+33)x10)/(20+33)
V2=(33x10)/53
V2=330/53 =approx 6 pints - Calculate partial pressure of Oxygen in 67 ft of salt water. (in psi)
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P02 = (D+33) x .445 x .2
P02 = (67+33) x .445 x .2
P02 = 100 x .445 x .2
P02 = .089 psi - A sport diver has developed a case of the bends. What mistake has the diver made?
- Stayed too deep for too long.
- List 3 things to prevent getting the bends.
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Plan dive/dive plan
don't dive too deep
drink plent of fluids before
ascend properly
make a safety stop - What are the primary symptoms of the bends?
- Pain in the joints after dive, fatigue, skin itches, dizziness, numbness, tingling, paralysis...
- What is the medical treatment for the bends?
- Use 100% oxygen with a demand regulator. Then recompression chamber.
- A sport diver has developed an air embolism. What mistake did the diver make?
- Not properly vented air volume building in lungs. Held breath on ascent.
- How could a diver prevent getting an air embolism?
- Don't hold breath, breath normally, don't dive if lungs are congested, ascend at 30ft/min or slower.
- What are the primary symptoms of an air embolism?
- Unconsciousness and/or bloody froth in mouth.
- What is the treatment for an air embolism?
- 100% oxygen on demand regulator, then recompression chamber.
- Where are are the bubbles lodged in a diver with a ruptured lung for the followin: a) air embolism, b) subcutaneous emphysema, c) mediastinal emphysema, d) pneumothorax ?
- a) brain b)under the skin of the neck and shoulders, c) center of chest cavity surrounding heart, d) between lungs and the walls of the chest cavity
- What is the recommended safe rate of ascent for a diver?
- 30 ft/min or slower.
- What are the 2 types of nitrogen narcosis?
- warm/clear water: euphoric joyous sensation. cold/low visibility water: melancholy, gloomy, fearful.
- What is a major problem of nitrogen narcosis?
- Divers indifference to following safety precautions!
- What are symptoms of Carbon dioxide excess?
- Cyanosis (blue-black discoloration of the skin, lips, nails), rapid breathing, headache, dizziness, vommiting.
- How do you prevent carbon dioxide buildup?
- Normal deep and continuous breathing. Avoid heavy exercise. If breathing hard, slow and catch breath.
- What are the 3 triggers that urge us to breathe?
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1) High carbon dioxide level
2) Low partial pressure of oxygen
3) Decreased lung volume. - By law, how often must a SCUBA tank be hydrostatically tested?
- Every 5 years
- How often must tanks be visually inspected?
- Every year
- What is the purpose of a "burst disk" in a tank?
- Part of the tank valve which will rupture at a certain pressure, safely venting the tank.
- Why should you always return from a dive with 500 psi remaining in your tank?
- 1) safety: it's important to have some reserve, just in case. 2) prevent moisture from getting into the tank.
- Why shouldn't you breath a tank dry?
- Having some air in tank prevents moisture from getting in.
- What is the approximate pressure in the 1st stage of a 2-stage regulator?
- 140 psi (120-180 psi)
- What is the approximate pressure of the 2nd stage of a 2-stage regulator?
- The ambient pressure at the 2nd stage.
- What is the difference between a "J" valve and a "K" valve?
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K = on/off
J = constant pressure reserve (about 300 psi) - What is the purpose of a "dust cap"?
- To keep moisture out of the first stage of the regulator.
- What information can you obtain from the markings on the neck of a tank?
- Date of manufacture, manufacturer, material, serial number, subsequent hydro dates, working pressure