Near miss: Sudden loss of air from diver bail-out bottle
- Safety Flash
- Published on 15 September 2020
- Generated on 25 February 2026
- IMCA SF 27/20
- 2 minute read
What happened?
A diver was returning to the dive basket to be recovered when he heard a “popping” sound and realised his first-stage regulator appeared to have failed and the contents of his bail-out bottle were escaping.
His bail-out bottle contents went to zero. The diver was recovered to the surface without further incident.
The regulator maintenance history was as follows:
- A six-monthly full strip-down and full service of the regulator had been undertaken two months prior following the service manual. Our member noted that a full suite of all spares was carried for the regulator including all greases, and special service tools.
- A monthly service had recently occurred, where the regulator was opened, cleaned with fresh water, and had a diaphragm check and full function test.
What were the causes? What went wrong?
Investigation revealed that there had been a failure of a roll diaphragm from an Xstream first stage regulator attached to the diver’s bail-out bottle (Photo 1 below).
The regulator was stripped down to reveal worn structural fibres inside the diaphragm had weakened allowing a hole to form.
Photo 2 shows a comparison between the failed and new diaphragm. The damage can be seen on the right unit showing the exposed fibres.
Lessons learned
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The roll diaphragm was inspected during the six-monthly maintenance and was deemed good enough quality to remain in service. Human judgement is subjective in deeming this part serviceable.
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Our member noted that there was no clearly defined replacement criteria for the diaphragm; consideration was being given to replacing the part every six months.
Actions
- Follow manufacturer’s guidance;
- Enhanced company planned maintenance system to include that the roll diaphragm is to changed out in addition to the service kit items.
Related Safety Flashes
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IMCA SF 08/19
25 April 2019
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IMCA SF 14/09
2 October 2009
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IMCA SF 09/02
1 September 2002
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