Jan’s SPG was acting strangely on descent and there was some breathing resistance from her reg. However, it seemed to work and the resistance was only a nuisance. That is, until she struggled to draw a breath on the bottom.

The Diver

Jan was 40 years old and healthy, with over 10 years of diving experience and hundreds of logged dives.

The Dive

Before the dive, Jan and her buddy headed to the swim step to make their entries. They both liked to be the first buddy team in the water, so they rushed a bit.

Almost immediately, Jan noticed the needle in her analog SPG jumped every time she inhaled. As she exhaled, the needle would return to full pressure. She made a mental note to have the gauge checked on Monday. When she got to her planned max depth of 55 feet, it was almost impossible for her to breathe.

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The Incident

Jan was confused for a moment when she tried to breathe and nothing happened, but her training and dive experience quickly took over. She signaled to her dive buddy that she was out of air and her buddy quickly donated her alternate air source. They ensured Jan was under control before making a controlled ascent to the surface. They both exited the water with no problem.

Analysis

On the surface, Jan’s regulator breathed normally, and her pressure gauge worked with only a slight wiggle when she took a breath. It was only then that Jan realized the valve on her tank was nearly closed.

For many years, divers were taught to turn their air all the way on and then a half (or a quarter) turn back. While this advice served a purpose in the early days of diving, improvements in tank valve designs have made that unnecessary. However, this tradition is often still passed down from dive instructors to divers.

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Your regulator adjusts the pressure from the tank to the ambient pressure of the water. On the surface, there was enough air pressure in the system that Jan didn’t notice the valve was only partially open. But when she descended and the pressure around her increased, the regulator couldn’t deliver enough air to give Jan a full breath.

In their rush to get in the water ahead of the crowd, Jan and her buddy didn’t do a complete buddy check. In this case, whether Jan forgot she turned her air on and then did it again, only turning it off and then back on slightly, or whether someone else checked her tank and did the same thing is unknown.

When Jan realized she was in trouble, her training kicked in and she and her buddy got the situation under control quickly. Making an alternate air source ascent doesn’t have to be difficult, but many divers haven’t practiced it since their PADI Open Water Diver training. Jan handled the situation underwater well, but often divers who find themselves out of air underwater begin to panic. They either bolt for the surface or immediately grab for any air source—which may be the one in their dive buddy’s mouth. Rehearsing air-sharing techniques underwater and discussing these situations on the surface make it more likely you will handle a situation like this calmly. That can be the difference between a small incident and a major problem.

Lessons for Life

• Do a buddy check: Many problems can be completely avoided by doing a check before each dive.

• Turn your tank all the way on: Turning your tank valve back a quarter turn is not necessary with modern scuba cylinders.

• Practice emergency skills: Run through emergency skills like air sharing and mask removal to ensure you can perform them at a moment’s notice.