Glossary of SCUBA Diving - B

B

backmount

The practice of carrying a scuba set on the back of the diver, supported by a harness, backplate or BCD.

backplate

A plate, normally made from metal, which rests against the diver’s back, and to which the primary cylinders are attached. Held to the body by harness straps.

backward roll entry

also back roll entry

Water entry method in which the seated diver rolls backwards off the side of the boat, allowing the scuba cylinders to strike the water first.

bailout cylinder

A scuba cylinder carried by an underwater diver for use as an emergency supply of breathing gas in the event of a primary gas supply failure.

bailout valve

1. An open circuit demand valve built into a rebreather mouthpiece, or other part of the breathing loop, which can be isolated while the diver is using the rebreather to recycle breathing gas, and opened at the same time as isolating the breathing loop when the diver bails out to open circuit.

2. A valve which opens the gas supply from the bailout cylinder of a surface supplied diver, used in case of surface gas failure, usually mounted on the side of a diving helmet or full-face mask, or on a manifold block on the diver's harness.

band mask

Further information: Surface-supplied diving#Band mask

A heavy duty full-face mask with many of the characteristics of a lighweight demand helmet. In structure it is the front section of a lightweight helmet from above the faceplate to below the demand valve and exhaust ports, including the bailout block and communications connections on the sides. This rigid frame is attached to a neoprene hood by a metal clamping band, hence the name.

barotrauma

Injury caused by pressure difference.

basket

see diving stage

BC

BCD

see buoyancy compensator

beach master

see also dive marshal

A person on the beach who records when divers enter and exit the water. Typically used during recreational scuba training to keep track of the students, watch the gear, and provide assistance when required.

bell

1. diving bell (q.v.)

2. Short tug on a lifeline, used in pairs, for signalling purposes.

bell cursor

Mechanism or structure for guiding and constraining the motion of a bell when in the close vicinity of the deployment platform to improve handling in bad weather.

bell harness

A safety harness made of strong webbing, which is fastened around a diver over the exposure suit, and allows the diver to be lifted without risk of falling out of the harness.

bell man

Standby diver in the diving bell

bell run

The part of a bell dive operation from bell lock-off to bell lock-on (to and from the life support system)

bell umbilical

Further information: Umbilical cable#Diver

The combined supply and return hoses and cables for life-support, power and communications between a diving bell and the support platform

bends

Decompression sickness: Injury caused by bubble formation in the body tissues after hyperbaric exposure.

BIBS

Built in breathing system. A demand breathing gas supply system with external exhaust used to provide chamber occupants with breathing gases other than the gas used to pressurise the chamber. Used for treatment gases and emergency breathing gas if the chamber is contaminated.

block adaptor

Screw-in adaptor fitting which is fitted to a 200/240 bar DIN pillar valve to allow connection of a yoke regulator or filling whip.

blowdown

Procedure of pressurising a diving chamber or saturation habitat.

blowout

Uncontrolled release of crude oil and/or natural gas from a well after pressure control systems have failed.

blowout preventer

also BOP

A large, specialized valve used to seal, control and monitor oil and gas wells. Generally operated remotely by hydraulic ram.

bolt snap

A metal connecter comprising a hook with a spring loaded axial sliding rod which must be manually retracted to allow the hook to be clipped onto something or removed.

booster

also booster pump see also compressor

Machine used to increase pressure of a gas. Usually refers to the case where inlet pressure is above ambient pressure already.

BOP stack

Blowout preventer stack: An assembly of several blowout preventer rams which may be used to shut off a well.

bottom time

Time used in calculating decompression obligation from decompression tables. For most tables this is defined as the elapsed time from starting the descent to starting the final ascent to the surface, excluding ascent and decompression time.

bounce dive

1. also surface oriented dive: In commercial diving, bounce diving is the alternative to saturation diving. Any dive where the diver is decompressed directly after the dive.

2. In recreational diving, a bounce dive is a descent to maximum depth and then a direct ascent back to the surface with the minimal bottom time, in a dive profile resembling a spike.

BOV

see bailout valve

breathing gas

Gas supplied to the diver to breathe, either directly to the diver or to the hyperbaric environment of the diving bell, dive chamber or saturation habitat.

Broco cutter

A type of thermal lance initiated by an electric arc, in common use for underwater cutting work.

bubble models

Further information: Decompression (diving)#Bubble models

Decompression models based on the assumption that bubbles will form during non-symptomatic decompression.

BTV

Further information: Ear clearing#Methods

Béance tubaire volontaire: Voluntary opening of the Eustachian tubes to equalise the middle ear.

buddy breathing

Sharing breathing gas from one demand valve by two or more divers, generally after an out-of-gas emergency.

buddy check

A procedure carried out by scuba divers using the buddy system where each diver checks that the other's diving equipment is configured, fitted, and functioning correctly just before entering the water to dive.

buddy diving

A safety procedure where two or three divers monitor each other constantly during a dive and provide assistance or rescue when needed.

buddy system

A procedure where two divers look out for the safety of each other, and give assistance if the other gets into difficulty.

buoyancy compensator

also BC, BCD, buoyancy compensator device, ABLJ, horse collar, stabilisor jacket, stab jacket or wing

An airtight bladder worn by a diver which can be filled with air and vented to adjust and control the buoyancy of the diver.

buoyancy control

The skill of maintaining the appropriate buoyancy at any time during a dive.

burst disk

A non-reclosing pressure relief device used to protect a diving cylinder from overpressurization.

butt-plate

A rigid or fairly stiff flexible lower extension to a backplate or other scuba harness supporting butt-plate rails, used for clipping off the lower end of sidemount cylinders to the harness.