Incident during entry to diving bell
- Safety Flash
- Published on 28 May 2010
- Generated on 19 February 2026
- IMCA SF 03/10
- 2 minute read
A Member has reported an incident during a ‘routine’ operation on a diving support vessel (DSV) where a diving bell had been surfaced from 140 msw for maintenance.
What happened?
The bell had been returned to atmospheric pressure and the surface stand-by diver had been tasked with opening the door of the surfaced bell and inserting an air hose to be used to flush out the residual diving gas (4% O2 in He) to ensure a breathable atmosphere in the bell prior to personnel entering it.
Having opened the bell door the stand-by diver stood up and started to climb into the bell. He immediately started to suffer the effects of oxygen starvation, became confused and fell out of the bell. Due to the hypoxic effect of the bell atmosphere the stand-by diver lost consciousness for a short period of time on deck in the bell hanger area.
He recovered quickly with no apparent ill effects and had regained consciousness without the need for resuscitation before the medic arrived on the scene.
The member noted that entry into recently surfaced diving bells and chambers was a potentially hazardous activity despite the fact it is considered to be a ‘routine’ task.
The member issued instructions that personnel on all diving worksites should be made aware of this potentially serious incident and should take steps to ensure that low oxygen hazards are identified and suitably addressed (by access control, flushing and atmospheric monitoring) before any person was permitted to enter either a bell or a chamber that has recently been surfaced.
Members are reminded of the importance of robust confined space entry procedures.
IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of the entire offshore industry.
The effectiveness of the IMCA Safety Flash system depends on the industry sharing information and so avoiding repeat incidents. Incidents are classified according to IOGP's Life Saving Rules.
All information is anonymised or sanitised, as appropriate, and warnings for graphic content included where possible.
IMCA makes every effort to ensure both the accuracy and reliability of the information shared, but is not be liable for any guidance and/or recommendation and/or statement herein contained.
The information contained in this document does not fulfil or replace any individual's or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.
Share your safety incidents with IMCA online. Sign-up to receive Safety Flashes straight to your email.