Buoyancy Control Device
The buoyancy control device (BCD) Air is released from it via a valve or hose. These actions assist your lungs in determining your level of suspension in the water. It can also be used on the surface for floating, resting, swimming or rescue. A standard BCD must accommodate you and all your equipment at the surface. Its large diameter inflation/deflation hose needs to maintain the function of releasing air quickly and easily when you need it.
BCD must have a pressure relief valve to prevent overexpansion upon rising as well as a low pressure inflation mechanism that connects it to the air in your tank. Ensure a snug fit so it does not cause any discomfort when you inflate it. All these added features can become rather bulky, so ensure that your purchase is a streamlined product. Think of BCD as a lifejacket with submersion ability. One of its primary design functions is to allow the diver to maintain neutral buoyancy with all the heavy equipment that is required for the dive. Buoyancy Control Device can have the following features: • A low pressure direct feed that transports gas from diving cylinder and diving regulator to the BCD. • An inflation valve that allows gas from the direct feed into the bladders of the BCD. • A vent valve that allows gas to escape from the bladders of the BCD. • Most BCD has at least two vents: one at the extreme top and the other at the bottom of it. As air migrates to whichever part of the BCD is uppermost, the vent situated at the shoulder is used when upright and the vent situated at the diver's waist is used when inverted. • An over pressurization valve that automatically vents the bladders if the diver over inflates the BCD by ascending or by injecting too much gas. • A harness that the diver wears with straps around the torso and over the shoulders. • A plastic or metal backplate to support diving cylinders. • Pockets for carrying diving reel, buoys and decompression tables. • An integrated diving weighting system - pockets for lead weights with a quick release mechanism. Integrated weights can eliminate the need for a separate weight belt. • D rings or other anchor points, for clipping on other equipment such as torches, strobes, reels, cameras and stage cylinders. • Emergency inflation cylinders. This can either be a 0.5 litre air cylinder, filled from the diver main cylinder, or a small carbon dioxide cylinder. There is a risk that an emergency cylinder is accidentally opened during a dive causing a rapid ascent and barotrauma to the diver. Carbon dioxide, being poisonous at high partial pressures, is a dangerous gas to have in a BCD because the diver may inhale it from the bag underwater. Some types of BCD also built around the diver's scuba set or are built into its harness.
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