Catastrophic Regulator Failure

During a dive in the Solomon Islands, this diver’s regulator failed, shutting off
her gas supply. Although gear failures are usually associated with improper
maintenance or use, manufacturing defects are possible.
The diver was a 36-year-old woman of unknown experience or certification. She was on an eight-day dive trip in the Solomon Islands and was diving with a regulator she had purchased eight months earlier.

The Incident

The diver entered the water for her first dive of the day at about 7:45 a.m. with 2,900 psi of air in her tank. She descended along a wall to 91 feet in search of sharks. Soon afterward she ascended to a shallower depth, around 60 feet, taking photographs along the way.

She was diving alone, but about 16 other divers were spread out along the wall. She came upon another photographer but kept her distance to stay out of his shot. She encountered a fan coral; before photographing it, she did what she usually did: looked at her computer to check her depth and gas supply. At that time she was 53 feet deep and had around 1,100 psi remaining in her tank.

The diver recalled taking several photographs of the fan and then making a big exhalation. When she tried to take another breath, there was no air. She immediately grabbed her octopus regulator, expecting to get some air from it and again got nothing. Searching for someone close enough to help, she spotted the diver she had just passed and motioned to get his attention, but he was not looking toward her. The diver assessed that he was too far away for her to risk swimming toward him.

Already experiencing an involuntary "pulsing" urge to breathe, the diver decided to make an emergency assent. She recalled at one point seeing her computer display "000" as the time/air remaining.

On the way to the surface the diver again tried to breathe from her regulator but was unsuccessful. When she finally surfaced, the dinghy was close by, and she quickly got into it. She explained her situation and asked to be put on oxygen. At that point she looked at her dive computer, which read 900 psi. Confused, she tried breathing from both second-stage regulators again and could not get air from either one. The diver showed her computer to the boat operator and said, "There is air in the tank!"

Upon arriving at the resort, the manager put the diver on oxygen for about 20 minutes and checked the regulator's function by attaching it to another tank. He was able to get one breath from the full tank but got no air from any of the partially full tanks to which he attached the regulator next. The manager then took the diver's original tank, examined it thoroughly and found nothing wrong with it or unusual about it. The manager tested the diver's regulator again on a partially full tank after the next dive by asking a diver to end his dive with 900 psi. The regulator continued to fail and would not provide gas.

After sitting out of diving for 30 hours, the diver used her original tank with a new first stage. She had no additional problems. Weighing the evidence, the diver contacted DAN® and said, "I believe this was a catastrophic failure of my regulator first stage, and it failed closed."


Scuba regulators work in a "downstream" configuration: air flows down from a place of high pressure (the tank) to one of intermediate pressure (the low-pressure hose) and then to a place of low pressure (the diver). Because of this, they are often thought of as fail-safe — i.e., most failures will cause a free-flow of air rather than cutting off the air supply. Indeed, it is very rare for a first stage to fail in the way this diver described. This particular first stage had an automatic closer device designed to prevent incursion of water into the first stage when it is removed from the tank.

After reporting this incident, the diver contacted DAN a few months later to let us know that the manufacturer had posted a consumer safety notice on its website that recommended a "voluntary product check" because a component of that system may not have been tightened to the correct torque. According to the manufacturer, this might cause a "possible gas-flow failure during a dive." Any divers who own a regulator that has an automatic closer device should check the manufacturer's website for product safety notices.

It is important to note that solo diving, or diving without a companion close by, has gained popularity in recent years with the increased availability of "self-reliant diver" certification courses. A core element of many of these courses is the use of a redundant air source in case a failure such as this one occurs. Unfortunately, this diver was not carrying a redundant air source and needed to make an emergency ascent. Luckily it was her first dive of the day, and she had moved to shallower water during the dive, so she probably had not taken on as much inert gas as she otherwise might have. Both requesting oxygen and remaining out of the water were prudent measures. Fortunately, the diver suffered no ill effects and was soon able to return to diving.

© Alert Diver — Q1 Winter 2018