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Open Water Diving
| Question | Answer |
|---|---|
| What are the six components of the total diving system? | Snorkeling, exposure, delivery, information, buoyancy, accessory |
| What is the snorkelling system? | Allows you to move, breathe and see. Includes mask, snorkel, boots, fin and mesh bag. |
| What is the exposure system? | Comprised of pieces that keep you warm. |
| What is the delivery system? | Information plus life support system - which provides you with sufficient amount of breathing gas ie. air or nitrox. |
| Air vs nitrox | Air is made up of oxygen, nitrogen and other gases. Ratio between nitrogen and oxygen is 79/21. Nitrox has a higher oxygen concentration than 21%. |
| Benefits of using nitrox | Nitrogen absorption limits our ability to explore underwater. |
| What is the information system? | Dive computer which displays air, depth, time, temp, ascent and descent rates. |
| What is the buoyancy system? | Allows you to achieve precise buoyancy control including surface floatation, controlled descents, proper swimming attitude at depth, and controlled ascents back to the surface |
| What is the accessory system? | Anything that makes diving more enjoyable for you,. Special tools, repair parts, |
| What does SCUBA stand for? | Self-contained underwater breathing apparatus. |
| As you dive ten metres, how many bars of pressure are added? | 1 bar/atmosphere |
| How much heavier is seawater/freshwater than air in terms of pressure? | 800x |
| What is Boyle's law? | If the temperature remains constant, as pressure increases, volume decreases. As pressure decreases, volume increases. |
| What is pressure? | Force per unit area |
| What is absolute pressure? | Total pressure exerted on an object. Includes 1 bar exerted by the air that is above the surface plus whatever pressure is exerted by the water at depth. Expressed in bars |
| What is a dive gauge? | They measure air tank pressure |
| What is gauge pressure? | Pressure readings on gauges |
| How do you determine gauge pressure? What is the gauge pressure at zero? | Gauge reads zero at one bar. Gauge pressure may be found by subtracting one bar from absolute pressure. Absolute pressure at sea level is 1, therefore gauge pressure is zero. |
| What is the pressure increase per meter of descent? | The pressure increase per meter of descent in salt water is 0.1 bar (1 bar / 10 m). |
| When do pressure related diving injuries occur? | When a sufficient pressure differential exists between absolute pressure and the pressure in the air spaces in our body |
| What is the formula for Boyle's law? | P1V1 = P2V2 |
| What is the volume of a flexible air-filled container at 0m, 10m, 20m and 30m. | 1, 1/2, 1/3, 1/4 |
| What protects against the 'squeeze', the uneven application of pressure? | Pressure equalisation |
| What body spaces can be subjected to the squeeze? | Ears, sinuses, lungs, teeth and intestines. |
| How does pressure affect the ear? | External pressure on the tympanic membrane increases, pushing the eardrum inward. If the diver fails to introduce additional air into the middle ear through the Eustachian tube, ear squeeze can occur. |
| How do you prevent ear squeeze? | Swallowing, rotating the jaw and the Valsava Technique |
| What is sinus squeeze? | Occurs when congestion traps air in a diver's sinus. As the diver descends, increasing pressure can cause the sinus membrane to rupture. If this happens, the result is that air in the sinuses is replaced by blood tissue in a process of pressure equalisati |
| How can you easily prevent sinus squeeze? | Avoid diving with a cold or congestion. Never use decongestants. |
| What is lung squeeze? When does it occur? | Only occurs when free-diving or snorkelling. If you descend even 1 or 2 metres below the surface without filling you lungs with air, the water pressure can compress the residual volume of air in your lungs. |
| How do you prevent lung squeeze? | Completely fill your lungs with atmospheric air prior to descending, staying above 20m and not releasing this air until surfacing. |
| What are the two kinds of equipment related squeeze? | Mask and suit squeeze. Prevented by properly fitted garments. |
| What is the Valsava Maneuver? | Open the normally closed eustachian tubes, allowing higher pressure from your throat to enter your middle ear. Most divers are taught to equalise by pinching their nose and blowing gently. |
| When should you perform the Valsava technique? What should you not do? | Only after swallowing and rotating jaw do not work. Do not blow to hard or try to force air into the middle ear. |
| What are the rules for equaliation | Breathe continuously - never hold your breath Equalise immediately and continuously throughout your descent. Never dive with a cold or congestion |
| What should you do if pain develops? | Stop your descent using your fins or line and ascend until the pain stops. Try equalising again. If you feel pain on the ascent, immediately stop and slowly ascent again. |
| What are reverse squeezes? | Reverse squeezes only happen on ascent. As the absolute pressure decreases, volume of air-filled spaces increases. |
| How do you prevent reverse squeezes? | Ascend extremely slowly or even stop occasionally to allow trapped gas to escape. |
| What are some examples of reverse squeezes? | Trapping air in sinuses, tooth squeeze, intestinal squeeze. |
| How to prevent intestinal squeeze? | Avoid eating gas producing foods prior to diving. |
| How do you clear water from your mask? | Tilt your head back, apply pressure to the top rim or mask and start exhaling gently through the nose. |
| How do you clear water from your snorkel? | Exhale sharply |
| What happens to your vision underwater? | Refraction - light waves bend as they pass from water into the airspace in your mask. This makes objects look 33% larger ad 25% closer. |
| What is the hand signal for ok, not ok, up, down, low on air | asdfasdf |
| The condition in which certain colours are diminished at depth is called | absorption |
| The absolute pressure expressed in terms of bar at 30 meters in salt water is | 4 bar |
| Describe sound transmission underwater | Sound travels farther Travels 4 times faster than on land It is difficult to discern the direction sound is coming from |
| Absolute pressure expressed in terms of bar at 10 metres in salt water is | 2 bar |
| Why is it so easy to become hypothermic underwater? | Water is an excellent conductor. Water absorbs your body's heat much faster than air does. |
| What are the three ways you lose body heat while diving? | Internal conduction, external conduction and convection |
| What is external conduction | Most heat loss for divers occurs this way. Direct transfer of heat energy from molecule to molecule. Body simply giving of heat |
| What is internal conduction | When we are breathing compressed gas at depth, we use internal body heat to warm the gas we're breathing |
| What is convection | Its the constant movement of water across our bodies. As our bodies warm the cooler water molecules that surround us move away and are replaced with colder one in a never-ending cycle. |
| How does temperature affect nitrogen levels? | Maintaining warmth is essential for the proper absorption and elimination of nitrogen |
| How do you keep your body warm? | Wear exposure protection with the proper thickness, fit and seam integrity. |
| What does thickness solve heat loss for | External and internal conduction |
| What does fit and seam integrity solve heat loss for | Heat loss through convection |
| How do wetsuits keep you warm? | Made of evenly blown neoprene, made of air or nitrogen gas in closed cells. Gas bubbles insulate you and keep you warm |
| The more nitrogen the material has the ____ you will be underwater. Why? | Warmer! Nitrogen is denser and less susceptible to compression. This enables bubbles to retain its insulating properties. |
| What is drysuit diving used for? | Used for cool to cold water conditions. Air is pumped into suit via an inflation valve for thermal and suit squeeze protection |
| How do you look after your wetsuit after diving? | Soak your wetsuit with wetsuit shampoo and hang to dry. Never store your suit folded or compressed. |
| The most efficient breathing pattern for scuba is... | deep inhalation followed by an even exhalation — deep, balanced and rhythmic. |
| Do we breathe more or less air underwater | More! 6-12 L on land, 12-15L underwater |
| Air consumption increases in direct proportion to | the depth you are diving |
| For example, a diver at two bar absolute (10 m) uses ___ as much air as a diver on the surface at one bar absolute. | twice |
| A diver at five bar (40 m) uses ___ as much air as a person on the surface. | five times |
| When diving the proper swimming position, attitude, is.. | 15-20 degrees above horizontal |
| How do you descend using your BC? | Let air out of BC slowly |
| How do you maintain neutral buoyancy? | As you descend, your suit will compress and you simply add small amounts of air to your BC to remain neutral. |
| Once you reach the surface how do you achieve positive buoyancy | fill your bc! |
| What is buoyancy? | Is when a fluid pushes up on an object immersed in it. |
| What is archimedes' principle? | An object immersed in an object will be buoyed up by a force equal to the weight of the volume of the liquid displaced. |
| What is positive buoyancy? | An object that weighs less than the weight of the liquid it displaces will float. |
| What is negative buoyancy? | An object that weighs more than the weight of the liquid it displaces will sink. |
| What is neutral buoyancy? | An object that weighs equal to the weight of the liquid it displaces will remain neutral, not sinking or floating. |
| What is the first step for scuba assembly? | Pre-soak your BC strap to prevent the cylinder from becoming loose underwater. |
| What is the second step for scuba assembly? | Face the cylinder valve away from you. |
| What is the third step for scuba assembly? | Place your BC at the proper height on the cylinder by using the height adjustment strap (if available). |
| What is the fourth step for scuba assembly? | Secure your BC to the cylinder. |
| What is the fifth step for scuba assembly? | Check and inspect the cylinder O-ring or DIN fitting O-ring for cuts |
| What is the sixth step for scuba assembly? | Standing behind the cylinder, position your Delivery System with the primary regulator over the right side and the Information System on the left side and gently tighten. |
| What is the seventh step for scuba assembly? | Before turning on the breathing gas, check the primary regulator and alternate by inhaling gently — you should not be able to breathe. |
| What is the eighth step for scuba assembly? | Attach the power inflator hose to your BC. |
| What is the ninth step for scuba assembly? | Face your Information System down and away from you and close to the cylinder. |
| What is the tenth step for scuba assembly? | Turn the breathing gas on slowly all the way and then turn back a half-turn. |
| What is the 11th step for scuba assembly? | Inflate your BC fully, check function of pressure relief and dump valves, leave your BC fully inflated and monitor for possible leakage and release air after successful leak test. |
| What is the 12th step for scuba assembly? | Check the performance of your regulators and the quality of breathing gas by pressing the purge valve. Clean breathing gas is colorless, odorless, and tasteless. |
| What is the 13th step for scuba assembly? | Once complete, place your Delivery and Information Systems inside your BC and secure it by laying the unit down. |
| How do you perform scuba disassembly? | Simply reverse assembly order. Only difference is to turn breathing gas off. Must purge all breathing gas from delivery system before removing the cylinder. |
| Never dive with a cylinder with gas that has... | an odour or taste |
| What is the first rule of scuba? | Breathe continuously! |
| What is the second rule of scuba? | Ascend slowly and maintain control! |
| What is the third rule of scuba? | Never dive alone or beyond level of training! |
| A high pressure scuba cylinder should be stored? | Secured and with a minimum of 30 to 50 bar |
| Under the SSI Equipment Service Program, your Delivery System should be serviced and performance checked | Every year! |
| Assuming a consistent air consumption rate, diving at a pressure of 4 bar will use __ as much air as diving at 2 bar. | 2 times |
| During normal diving activities, divers should never exceed an ascent rate of __ meters per minute. | 9 metres per minute |
| Describe the process of respiration part 1 | Inhaled o2 move from inside the alveoli through the tissue layers into pulmonary capillaries. C02 is then transferred from the blood into the alveoli to be expelled when you exhale. |
| Describe the process of respiration part 2 | Blood from pulmonary capillary bed, flows into left side of heart through pulmonary vein. Blood is pumped out via aorta towards tissues. |
| Describe the process of respiration part 3 | Diffusion takes place again. 02 diffuses out of blood into tissues and c02 building up in tissues diffuses into blood. |
| Describe the process of respiration part 4 | Blood is transported through the veins to the right side of the heart, pumped into pulmonary arteries and then into pulmonary capillary bed |
| What is diffusion? | Movement of gas from a higher concentration to a lower concentration |
| What are the 4 overexpansion injuries? | Arterial gas embolism (gas bubbles enter vessles, expand and block circulation) pneumothorax, subcutaneous emphysema, mediastinal emphysema |
| What are all 4 overexpansion injuries caused by? | Breathing gas escaping into the various tissue layers of the chest or lungs. Caused by holding breath upon ascent. Air in lungs expands as pressure decreases and alveoli rupture. |
| Never ever let freedivers or snorkelers breathe from your | Delivery System, not even at a shallow depth of 1 m. |
| How do you prevent overexpansion injuries? | Breathe continuously - never hold breath Do not dive with respiratory congestion Don't smoke Ascend slowly Use right equipment |
| When do overexpansion injuries occur? (in general) | On the ascent |
| When does decompression sicknesses occur? (in general) | Caused by various gases under pressure on descent |
| What causes Caisson's disease/the bends/decompression sickness? | Breathing gas under pressure causes large amounts of N into body. N stays in solution as long as pressure is maintained. If diver ascends too quickly, suddenly reducing pressure, n will come out of solution and form bubbles in tissues and blood. |
| What is Dalton's law? | Total pressure of a mixture of gases equals the sum of the partial pressures. |
| What is henry's law? | The amount of gas that will dissolve in a liquid is directly proportional to the partial pressure of the gas. |
| Describe the physiology of nitrogen and its role in decompression sickness in detail. part 1 | N enters body during respiration and is absorbed into blood and tissues. Tissues absorb N proportional to depth of dive and increased partial pressure. |
| Describe the physiology of nitrogen and its role in decompression sickness in detail. part 2 | A diver returning from depth to the surface may be supersaturated with N. If diver surfaces with N conc. in the tissues that exceeds M-value, nitrogen bubbles can form in blood |
| Describe the physiology of nitrogen and its role in decompression sickness in detail. part 3 | Nitrogen bubbles can block circulation and cause decompression sickness |
| What is the major symptom of decompression sickness? | Pain in joints (poorly perfused, therefore unable to eliminate N) |
| How do you prevent decompression sickness? | Constantly observe computer for depth, remaining time, remaining gas, slow ascents and safety stops Stay warm, do not exercise heavily 6 hours prior to flight |
| How do you make a proper ascent? | Follow dive plan. If you start on surface with 210 bar of air, use rule of three thirds. 70 bar to explore, 70 bar to return to your ascent point and 70 bar for your ascent and safety stops |
| How often should you make a safety stop and for how long? | 5 meteres for 3 to 5 min |
| Why should you wait to fly after diving? And for how long? | Should always wait 24 hours. Diver may be supersaturated with nitrogen. As you ascend in a plane, pressure decreases possibly leading to decompression sickness |
| What is nitrogen narcosis? When does it occur? | Nitrogen under high pressure produces narcotic effect. Typically only takes place at 30 metres (4bar). N has affinity for lipids. Thought to pack myelin sheath and slowing nerve impulse across synapses. |
| What is oxygen toxicity? When does it occur? | High concentrations of 02 can be poisonous. Occurs when partial pressure of o2 is 1.6 bar |
| How do you prevent oxygen toxicity? | Never dive with pure oxygen as your main gas. Never exceed a partial pressure 1.4 bar |
| How do you prevent C02 buildup (hypercapnia)? | Breathe continuously, always maintain neutral buoyancy to limit exertion, if overexerting stop and or surface carefully, stay within diving limit of 30 m, wear a high quality, personally fitted total diving suit |
| What is the process behind carbon monoxide poisoning? | CM binds with heam 200x more readily than 02. Therefore blood cannot carry enough 02 to meet tissues' needs. |
| How to prevent carbon monoxide poisoning? | Obtain gas from reputable source Keep it away from gas exhaust |
| The most serious lung overexpansion injury is: | Arterial gas embolism |
| Haldanes theory that the human body can withstand a 2:1 pressure ratio was revised by D Workman to a nitrogen ratio of: | 1.58:1 |
| In air at 1 bar, the partial pressure of nitrogen is___, oxygen is_____. | 0.79/0.21 bar |
| The major, and most common, symptom of decompression sickness is: | joint pain |
| If a flexible air-filled container at 30 meters of sea water has a volume of 6 liters, what would be the volume if it were transported to the surface? | 24 L |
| How do you prevent accidents following one simple rule? | we must track the amount of dissolved nitrogen in our bloodstream and tissues throughout the diving day and week via dive computer |
| Define depth | The deepest point reached during the dive |
| Define bottom time | Amount of elapsed time since the start of your descent and the start of your ascent |
| Define surface interval | Amount of time diver stays on surface between dives |
| Define repetitive dive | Any dive started more than ten minutes and less than 12 hours after a previous dive |
| Define No Decompression limits | Max time allowed at depth without having to perform a mandatory decompression stop during ascent |
| Define no decompression dive | Any dive made to a depth and time that allow a direct ascent to the surface without mandatory decompression stops. |
| Define residual N | Residual nitrogen is the amount of excessive nitrogen dissolved in our bloodstream and tissues after a dive and all previous dives in a series. |
| Define decompression dive | Any dive which exceeds the No-Decompression Limits at a certain depth, so that a direct ascent to the surface is not possible and mandatory decompression stops must be made. |
| How to identify a rip current? | Looks for break in surf line caused by out-rushing water. Rips currents always move away from the beach on a line that is almost perpendicular |
| How do you escape a rip current? | Never try to outswim a rip current. Swim parallel to beach for a few meters |
| What is the most common entry? | In a giant stride, with the BC slightly inflated, the diver simply steps off into the water in a long stride, looking forward, not down. |
| How to perform a controlled descent? Part 1 | On surface in a vertical position, release air from BC until water covers top of head. Stop releasing air and exhale, while simultaneously forward to the diving (prone, parallel) position |
| How to perform a controlled descent? Part 2 | You'll take first breath at a depth of one meter and neutrally buoyant. 1 meter depth is also the starting point to equalize |
| As you descend you need to constantly | You will need to stop swimming, adjust your buoyancy, equalize, descend, stop, adjust your buoyancy |
| emember, if you experience ear squeeze, swim back.... | to the depth where the squeeze is relieved, maintain the depth, and try equalizing again. |
| How to perform a controlled ascent? | Hold BC exhaust host in left hand and dive computer in right hand. Look up during ascent. On the surface, inflate your BC for surface flotation. |
| The slower the ascent rate from __ meters to your safety stop, the better. Why? | Ten metres. The greatest relative pressure change takes place from 0 to 10 meters. The |
| The greatest relative pressure change takes place from 0 to 10 meters. The | Depth, Gas consumption based on experience, breathing pattern, amount of work performed. |
| I’m out of air and… Out of air. Situation 1: My buddy is close enough to help. | Your first choice should be a dependent action: Sharing Air. |
| Situation 2: The surface is closer than my buddy. | Your choice is the independent action: Emergency Swimming Ascent. |
| ituation 3: My buddy is lost and the water is too deep for the Emergency Swimming Ascent. | Your choice is the independent action: Emergency Buoyant Ascent. |
Created by:
Lui24