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90 Cards in this Set
- Front
- Back
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Open Circuit scuba systems:
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are the most common type of recreational scuba equipment, are easy to use and maintain, and vent exhaled gases directly into the water.
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All rebreathers recycle ______ instead of allowing them to be wasted into the water.
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Usable gases
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Identify the six components of a recreational scuba system:
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BCD inflation system, regulator, BCD, SPG, Alternate air source, and weight system
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Which of the following cylinder markings designates the type of metal used to construct the scuba cylinder?
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3AL, as 1777
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Which of the following cylinder markings designates the hydrostatic test date?
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7@89
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The (+) designation that appears on ________ cylinders denotes that the cylinder may be overfilled to ______ beyond it working pressure.
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Steel/10%
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True or False: Aluminum cylinders were introduced because aluminum is stronger metal and enables higher working pressures than steel cylinders.
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False – aluminum was introduced due to its advantage that it is less subject to structural weakening due to corrosion
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A steel cylinder whose capacity is 2016lliters/71.2 cubic feet at 168bar/2475psi and aluminum cylinder whose capacity is 3000liters/100cubic feet at 203bar/3000psi are both filled to 133bar/2000psi. Which cylinder contains more air?
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71.2cuft/2475psi=.029 for steel & 100cuft/3000psi=.033 for aluminum; 2000psi*.029=58cuft for steel &2000psi*.033=66cuft for aluminum
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True or False: During a hydrostatic test a scuba cylinder is placed in a water-filled chamber. The cylinder is then filled with compressed air and the amount of expansion that occurs in the cylinder is measured by the amount of water that is displaced.
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False-filled with water not air
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To what pressure is a scuba cylinder filled during a hydrostatic test?
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5/3s of its working pressure
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Under what circumstances should a scuba cylinder be visually inspected?
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If loose material is heard rolling around inside the cylinder, if red or green accumulations is seen in the filter of the regulator first stage, or once every year even if the cylinder appears in good condition.
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Why perform a visual inspection on a scuba cylinder?
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To detect exterior damage such as severe scratches or dents, to detect severe interior corrosion, particularly in steel cylinders and to prevent galvanic action between the dissimilar metals of the cylinder and valve threads.
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Match the label of the items to the corresponding letter then lock the label to the letter by moving it left:
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high pressure opening, cylinder O-ring, on-off knob, high pressure seat, O-ring for sealing regulator, debris or dip tube, and burst disk
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The two basic types of cylinder valves used today are:
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yoke and DIN
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What device prevents an over-pressurized cylinder from exploding?
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Burst disks
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The fundamental function of the first stage of an open circuit regulator is to:
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reduce the high pressure delivered by the cylinder to an intermediate pressure.
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Identify the five components of an open circuit scuba regulator.
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Alternate second stage primary second stage, SPG& instrument console, Low pressure inflator hose, first stage
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The fundamental function of the second stage of an open circuit regulator is to:
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reduce the intermediate air pressure to ambient pressure for breathing
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If a regulator, a valve that tends to open in the direction of flow is referred to as ______. This type of valve is considered to be a _____ design.
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Downstream/fail-safe
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An environmental seal operates by:
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not allowing water to directly contact the first stage piston or diaphragm
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The advantage of a balanced first stage over an unbalanced first stage is:
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they breathe easier at greater depths, even at low cylinder pressures, they provide greater air flow, and they are better able to supply a second diver breathing from an octopus.
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A submersible pressure gauge (SPG) is used to:
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tell you how much breathing gas you have left in your cylinder at any time.
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An analog SPG uses a ______ to determine cylinder pressure.
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Bourdon tube
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Why do you need to know the maximum depth of a dive and how long you’ve been underwater?
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To avoid decompression sickness and remain within your planned depth and time limits
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Most depth gauges used today are:
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digital
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A capillary depth gauge works by using:
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Boyle’s law
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What situations dictate a need for a compass?
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When diving in low visibility water, when diving in mid-water, when diving at night, and when you can’t use natural references to navigate
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Match the features to their corresponding letters on the diagram.
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Numerical degree marking, movable bezel, magnetic North pointing needle, index marks
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The illustrated compass is a ______ type.
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Indirect reading - numbers going up in a counter clockwise direction
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You can use a dive computer to:
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keep nitrogen levels in your body within accepted limits
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True or False: A dive computer constantly tracks your depth and time on a dive, and then applies the information to a mathematical model to compute the theoretical nitrogen in your body.
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True
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The pressure sensor or transducer of a dive computer informs the computer of which decompression model or algorithm to use while diving.
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False
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Advantages dive computer have over dive tables include:
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easier dive planning and following the plan, offsetting human error, and more time underwater.
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You and your buddy can’t share a dive computer because:
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variations of even a few feet can affect time limits
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Information all dive computers provide include:
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no decompression time remaining, time, depth, ascent rate, and emergency decompression
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The first step in setting up and using your dive computer is:
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reading the manufacturer’s instructions
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Depending upon the model, you may activate your computer by:
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Pressing a button or touch contacts with moist fingers
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To plan a dive with your computer:
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scroll the NDLs to find the limit for your planned depths, agree on a time limit with your buddy, write down the NDL for your planned and next greater depth, and plan dives so the maximum depths are progressively shallower.
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When flying after a dive with your computer, it’s recommended that you:
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follow the dive medical community recommendations or when the computer says you fly – whichever is longer
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Guidelines to follow when diving with a computer include:
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staying well within limits, following the most conservative computer, watching your SPG, and ascending slowly and making safety stops
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If your computer fails:
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during a dive, use your backup computer if you have one, between dives, use your backup computer if you’ve been diving with one, or you may be able to resume diving using tables
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True or False: You should not turn off your computer (or remove the batteries) between dives, because that would cause it to lose any memory of previous dives, which could cause it to calculate repetitive dives incorrectly and create an unacceptable DCS risk.
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True
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The primary concern regarding enriched air and scuba equipment is:
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the contact with high oxygen content may cause fire, explosion or deterioration
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When using enriched air with up to 40% oxygen:
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generally, you may use standard scuba equipment (except cylinder), use of oxygen compatible lubricants is generally recommended, and follow all manufacturer recommendations regarding using their equipment with enriched air
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Enriched air requires a dedicated cylinder because:
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it can be hazardous to unknowingly dive with enriched air and it can be hazardous to blend enriched air in conventional air cylinder
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Based on broadly accepted international dive community practices, enriched air cylinders should have the following markings/colors/tags:
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yellow cylinders should have a 10cm/4in green band at the shoulder with “Enriched Air”, “Enriched Air Nitrox”, “Nitrox” or a similar designation, the cylinder should have a visual service sticker, the cylinder should have sticker (decal) to indicate whether it is oxygen service rated, and the cylinder should have a contents sticker (decal) or tag
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If an oxygen service rated enriched air cylinder is filled with standard compressed air, you should:
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have it serviced by someone qualified to work on enriched air equipment before exposed to more than 40% oxygen again
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The two most common blends of enriched air are:
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EANx32 and EANx36
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______ scuba systems are the most common type of recreation scuba equipment, are easy to use and maintain, and vent exhaled gases directly in to the water.
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Open Circuit
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The term “Open Circuit” refers to the fact that:
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the exhaled air is released directly into the water
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All rebreathers recycle ____ instead of allowing them to be wasted into the water.
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Usable gases
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Which of the following tank markings designates the type of metal used to construct the scuba tank?
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3AL
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Which of the following tank markings designates the hydrostatic test date?
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7@89
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The (+) designation that appears on _______ tanks denotes that the tank may be overfilled to ______ beyond its working pressure.
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Steel/10%
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True or False: Typically, aluminum cylinders have higher working pressures so they hold comparable or slightly more air than steel cylinders.
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True
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True or False: During a hydrostatic test a scuba cylinder is placed in a water filled chamber, the cylinder is then filled with water. As the water pressure with the tank is increased, the amount of expansion that occurs in the cylinder is measured by the amount of water that is displaced.
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True
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To ensure the structural integrity of a scuba tank, it should be ______ anytime it is _______.
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Hydrostatically tested/exposed to temperatures above 1800F
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During a hydrostatic test a scuba cylinder is generally pressurized to ______ of its working pressure.
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5/3’3
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Under what circumstances should a scuba cylinder be visually inspected?
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Air compressor defective or air smells unusual, the valve is removed, after hydrostatic re-test, cylinder exterior is damaged, burst disk fails, or its previous history is unknown
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Identify the indicated part of a cylinder valve.
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Debris tube
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Identify the type of valve pictured.
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DIN valve
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To prevent a scuba tank form rupturing due to over pressurization, a burst disk is installed in the ______, and is designed to rupture when the tank pressure rises above about _______ of the tank’s rated pressure.
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Valve/140%
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True or False: One advantage of an open circuit demand valve regulator is that it avoids carbon dioxide buildup by reducing dead air spaces.
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True
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The term “Demand Valve” refers to the fact that the regulator will provide air:
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only upon inhalation
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The fundamental function of the first stage of an open circuit regulator is to:
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reduce the high pressure delivered by the cylinder to an intermediate pressure
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Identify the component of an open circuit scuba regulator indicated in the photograph.
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Primary second stage
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The component of an open circuit scuba regulator that reduces the intermediate air pressure to ambient pressure for breathing is:
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second stage
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Fail safer refers to a regulator’s tendency to ______ because of the use of a(n) _______ valve in the second stage.
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Free flow/downstream
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A/An ________ operates by not allowing water to directly contact the first stage piston or diaphragm.
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Environmental Seal
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A valve that tends to open in the direction of flow is referred to as __________ while a valve that tends to close in the direction of flow is referred to as_______.
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Downstream/upstream
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The primary advantage of a _______ over an unbalanced one is that they breathe easier at greater depths, even at low tank pressures, provide greater air flow, and are better able to supply a second diver breathing from an octopus.
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Balanced first stage
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A ________ is used to tell you how much breathing gas you have left in your cylinder at any time.
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SPG
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Why do you need to know the maximum depth of a dive and how long you’ve been underwater?
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To avoid decompression sickness and remain within your planned depth and time limits
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An/A _______ depth gauge works by using Boyle’s law.
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capillary depth gauge
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While on a dive in a mountain lake at an altitude of 3,000meters/10,000feet, a diver checks his depth. He is using a capillary depth gauge which indicates a depth of 14meters/45feet. If he actually measured the linear distance to the surface from where he is, he would find that:
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he is actually less than 14meters/45feet below the surface
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What situations dictate a need for a compass?
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When diving in low visibility water, diving in mid-water, diving at night or when you can’t use natural references to navigate
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Identify the indicated component of a dive compass:
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lubber line
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Identify the indicated component of a dive compass:
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Index Mark
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The illustrated compass is a ____ type.
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Direct Reading
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You can use a _____ to keep nitrogen levels in your body within accepted limits.
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Dive computer
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The ______ of a dive computer informs the computer what depth it is at.
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Pressure sensor/transducer
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Two divers may use a single dive computer provided they are careful to remain together and dive the exact same profile.
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False
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A buddy team exits the water. Both divers using dive computers. After a short surface interval, they plan another dive to 18meters/60feet. One device allows 38 minutes of bottom time at 18meters/60 feet, the other allows only 32 minutes. Based on this information how should they plan their dive?
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Plan a bottom time of somewhat less than 32 minutes and make a safety stop before surfacing
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True or False: Before using your computer for the first time, you should read the manufacturer’s instructions.
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TRUE
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To plan a dive with your computer:
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scroll the NDLs to find the limit for your planned depth, agree on a time limit with your buddy, write down the NDL for your planned and next greater depth, and plan dives so the maximum depths are progressively shallower.
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You should not turn off your dive computer, or replace the batteries between dives, because that would cause it to lose any memory of previous dives, which could cause it to calculate repetitive dives incorrectly and create an unacceptable risk of _________.
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Decompression sickness
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If your computer fails:
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during a dive, use your backup computer if you have one, between dives, use your backup computer if you’ve been diving with one or you may be able to resume diving using tables
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When flying after a dive with your computer, it’s recommended that you ______ or when the computer says you can fly – whichever is longer.
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Follow the dive medical community recommendations
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When using enriched air with up to _____oxygen generally, you may use standard scuba equipment (except cylinder), use of oxygen compatible lubricants is generally recommended, and follow all manufacturer recommendations regarding using their equipment with enriched air.
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40%
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_____ and _____ are the two most common blends of enriched air.
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EANx32 and EANx36
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