Larry Wedgewood Scuba Diving Instruction

Lesson 12

BCD (Buoyancy Control Device)

Course Complete

Watch the video above and then answer the quiz questions below

The modern BCD has evolved from separate components that function best as a single unit. Its components include:

Inflatable bladder – This is a very durable bag that you inflate or deflate to change your buoyancy.

Cylinder band and harness/jacket – The bladder integrates with an adjustable harness that holds the cylinder on your back. The bladder may be entirely behind you, or wrap partially around your waist and/or over your shoulders. With some systems, you can interchange harnesses and bladders to accommodate sizing and preferences.

LPI (low pressure inflator) mechanism – Usually at the end of a large-diameter hose, the LPI inflates the bladder with air from your cylinder, via the regulator, when you press a button. Another button allows you to deflate the bladder, or inflate it orally.

Overpressure/quick exhaust valves – To prevent rupturing the bladder due to overfilling, BCDs have one or more overpressure valves that automatically vent if the BCD is too full. Some may have “quick dump” valves that let you manually release air, which is sometimes easier (due to your position in the water) than using the LPI exhaust.

Weight system – Many BCDs have special weight pockets that you can release and drop in an emergency. The more weight you need (like when wearing a buoyant dry suit), the more useful these are. (More about weight systems shortly).

BCD inflator, deflator and weight systems vary. Your instructor will show you the specifics for the BCD you use.

Quick Quiz

Module One

Water Pressure and Air Volume Effects

The Effects of Increasing Pressure on Body Air Spaces Topic 2 of 6

The Effects of Decreasing Pressure on Body Air Spaces Topic 3 of 6

Breathing Underwater

Buoyancy and Controlling Buoyancy Topic 5 of 6

The Buddy System

Choosing and Caring for Scuba Equipment

Dive Masks

Snorkles

Fins

Scuba Kit