How Much Air Should Be in Your BCD?

If you're underwater during a dive, the correct amount of air in your BCD is zero.

That statement surprises many divers, but proper buoyancy comes from correct weighting and breathing control — not from constantly inflating and dumping your buoyancy compensator.

Watch: Why You Have Too Much Air in Your BCD

In this video Freddy explains why divers are commonly overweighted, how that leads to constant buoyancy adjustment, and how to fix it.

Why Divers Think They Need Air in Their BCD

New divers are often intentionally overweighted during training. This helps instructors maintain control and keeps students near the bottom.

Unfortunately, many divers leave certification believing that adding air to the BCD is how buoyancy should always be managed.

The Problem with Air in Your BCD

Air compresses as you descend and expands as you ascend.

• As you go deeper, air volume shrinks.
• You add more air to compensate.
• As you ascend, air expands.
• You must dump air constantly.

This creates a moving target and constant buoyancy instability.

The Proper Goal: Neutral with Zero Air

Your objective underwater is to achieve neutral buoyancy using:

• Correct weighting
• Proper breathing control
• No air in the BCD

Your lungs provide fine control. Inhale slightly to rise. Exhale slightly to descend.

How to Check Proper Weighting

A practical test:

1. At 20 feet during your safety stop
2. With approximately 800 PSI remaining
3. With a half lung of air

You should be able to hover motionless.

• If you sink → too much weight
• If you float → too little weight

Where to Get Help

FAQ

Should I have air in my BCD underwater?

No. Proper buoyancy underwater should require zero air in the BCD once correctly weighted.

Why was I taught to add air?

New divers are often overweighted during training for control and safety.

How do I improve buoyancy control?

Practice proper weighting and breathing techniques. Remove excess lead and rely less on BCD inflation.