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Glossary - C

C Card Certification Card. Usually the same type and size as a credit card.
CAGE Coronary Arterial Gas Embolism. A lung over-expansion injury that involves air bubbles escaping from the lungs into the pulmonary capillaries. The bubbles can then travel to the heart and eventually follow the circulatory route to the brain. In severe cases, CAGE can be fatal. Treatment is immediate O2 breathing and transport to a recompression chamber. Also known as air embolism. Symptoms may be similar to DCS.
Caisson A watertight structure within which construction work is carried on under water
Carbon Dioxide (CO2) A gas generated by the metabolic process of generating energy to sustain life. Carbon Dioxide "CO2" is normally regulated through the breathing process where CO2 (with its high dissolved PPCO2) is moved out of the bloodstream, and Oxygen (with its high ambient PPO2) is moved into the bloodstream. In normoxic air the percentage of CO2 is negligible, about 0.03%. CO2 appears to be a factor in DCS, narcosis, hyperoxia and Hypoxia.
Carbon Monoxide Carbon monoxide (CO) is produced from the incomplete combustion of organic fuels, most commonly gasoline engines. Carbon monoxide is a colourless, odourless, tasteless gas, and it is largely because CO cannot be readily detected that it is so dangerous. Inhaled CO will bond with haemoglobin with an affinity 200 times greater than oxygen.
Cardinal Fundamental, of first importance. E.g. marks - North, South, East, West
Cardiopulmonary Resuscitation A process utilising the combination of external heart massage and mouth-to-mouth respiration (artificial ventilation) to artificially maintain the heartbeat and respiration of a victim.
Carotid-Sinus Reflex A tight hood or wet suit causing pressure on the carotid arteries can give a false high pressure signal and slow the heart unnecessarily: carotid-sinus receptors send impulses to the cardio inhibitory center of the brain
CBL Controlled Buoyant Lift, a method of lifting an unconscious casualty to the surface.
CCBA Closed Circuit Breathing Apparatus, a rebreather, a device that reuses air by scrubbing or removing the carbon dioxide from it. There are usually no or very few bubbles emitted.
CCR  Closed Circuit Rebreather
Celsius A unit of measure for temperature.
Celsius = (Fahrenheit - 32) / 1.8 or 5/9 (Fahrenheit -32)
Channel 16 The international distress channel on a VHF marine radio.
Charles Law Temperature has a direct relationship on pressure and or volume; heat will make the pressure increase, heat will also make a flexible object increase in size.
Chemical light stick A light source caused by two chemicals mixing and producing light. Divers attach these sticks to their equipment to improve their visibility, especially on night dives.
Chine A line formed by the intersection of the sides and bottom of a flat or v-bottomed vessel.
CI Club Instructor. A BSAC instructor qualification
Cleat A fitting, secured to the deck, mast or spar (strong pole used for ship's yard, boom, gaff, etc.) - having two projecting arms to which lines are made fast.
Clove Hitch A knot for temporarily fastening a line to a spar or piling. See Knots.
CMAS  Confederation Mondiale des Activities Subaquatiques (World Underwater Federation)
CNS  Central Nervous System
CNS Oxygen Toxicity The effects of breathing high-pressure O2. An extremely dangerous manifestation which can include convulsion and collapse. Although 1.6 Bar has been held as the standard limit by NOAA, many divers prefer to restrict their activities to no more than 1.4 Bar PPO2 for added safety. Recent tests by the US Navy suggest that CNS O2 Toxicity can be seen as low as 1.3 Bar PPO2. CNS O2 toxicity can be prevented by a reduction in the PPO2 in the breathing gas via a different gas mixture or via ascending.
Cocked Hat Where three bearings taken do not exactly intersect. Providing the triangle of calculation (cocked hat) is small enough (say less than 1 km across) the centre of the cocked hat may be taken as a fix (fixed position)
Compass Error Combined effect of variation and deviation.
Computer An electronic device either worn on the wrist or console mounted which  constantly displays information such as current depth, maximum depth, dive time and remaining no stop time. It can also calculate the decompression requirements for the dive and provide other information such as temperature ascent rates etc...
Conduction The transmission of heat via direct contact. Divers are most affected by conduction.  Water conducts heat 25 times faster away
from a person's body than air.
Contour Line joining points of uniform depth marked on a chart.
Convection The transmission of heat via fluids or gas. As these are warned they they rise and are replaced by cooler substances.
CPF  Chartwork & Position Fixing
CPR Cardio Pulmonary Resuscitation
CQR  Type of Anchor
CTC See Current Tissue Code
Current Flow of a large body of water in one direction.
Current Tissue Code The code which identifies a divers current nitrogen saturation level. Calculated from the last dive's surfacing code and the surface interval.
Cyanosis A bluish discoloration of the skin that results from an oxygen deficiency in the blood.
Cyclone Low pressure area In the Northern hemisphere, a cyclone circulates anti-clockwise and is usually associated with unsettled weather.
Cyclonic Winds that are variable in direction due to being close to the centre of cyclone.










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