A buoyancy compensator (or buoyancy control device, BC or BCD) is a piece of diving equipment worn by divers to provide:

» life saving emergency buoyancy both underwater and on the surface.
» the ability to adjust and control the overall buoyancy of the diver and the diver's heavy equipment allowing the diver to achieve neutral buoyancy, remaining at constant depth, or to descend or ascend in a controlled way.

Some types of buoyancy compensator also built around the diver's scuba set or are built into its harness.

Features

BCs can have the following features:

» A low pressure direct feed that transports gas from diving cylinders and diving regulator to the BC.
» An inflation valve that allows gas from the direct feed into the bladders of the BC.
» A vent valve that allows gas to escape from the bladders of the BC. Most BCs have at least two vents: one at the extreme top and the other at the bottom of the BC. As air migrates to whichever part of the BC 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 BC 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 reels, buoys and decompression tables.
» An integrated diving weighting system - pockets for lead weights with a quick release mechanism.
» D rings or other anchor points, for clipping on other equipment such as torches, strobes, reels, cameras and stage diving cylinders.
» Emergency inflation cylinders. This can either be a 0.5 litre air diving cylinders, 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, is a dangerous gas to have in a BC because the diver may inhale it from the bag.

Types

There are three main types of BC:

» Wings consist of inflatable bladders worn behind and to the side of the diver. They are a recent development and often used in technical diving. The diver is strapped to a back plate on to which the wings are attached. The spacious location of the bladders allows their volume and therefore their buoyancy to be high: 30 litre wings are not uncommon. Heavy equipment such as diving cylinders can be fixed to or slung from the back plate. A problem with wings is their tendency to float the diver facedown at the surface, which could be lethal in the event of the diver being incapacitated.
» Stab jacket, stabiliser jacket, stab, waistcoat, or vest BCs are inflatable vests worn by the diver around the upper torso, and also act as the cylinder harness. They typically provide up to 25 litres of buoyancy and are fairly comfortable to wear. They may float an unconscious casualty face-down.
» Adjustable Buoyancy Life Jackets, ABLJs or horsecollar BCs: are worn around the neck and chest with straps around the waist and usually between the legs. They are cheap, light and small, providing up to 15 litres of buoyancy. They float an unconscious casualty face-up. But they are old-fashioned, uncomfortable with a strap between the legs and provide less buoyancy than the other types. The diver must use a separate cylinder harness as a platform for the aqualung.

History

The ABLJ was developed by Maurice Fenzy in 1961. Early versions were inflated by mouth underwater. Later versions had their own air inflation cylinder. Some had carbon dioxide inflation cylinders, a development which was abandoned when valves that allowed divers to breathe from the BC's inflation bag were introduced. Since 1969 most modern BCs have used inflation gas from one of the diver's main gas cylinders. In 1971, Scubapro developed the Stabilizer Jacket, the first jacket-style BC, and in 1972 Watergill developed the Atpac wing.

More recent innovations for jacket BCs include, weight pouches to adjust attitude underwater, putting the weights on the BC rather than on a weightbelt, and integrated diving regulators. Innovations for wings include weight pouches to adjust attitude underwater, and the stainless steel backplate.

Buoyancy Compensator Tips

There are so many choices available when choosing a Buoyancy Compensator and this technology has improved significantly in the past few years. The questions below will help us to find the perfect BC for your needs and budget.