Hyperoxia Events Summary

 
 
1) What symptoms did you experience?
Strange feelings of "spaced out" type for a short while, just a feeling of not being right, followed by very bright lights at the sides of my field of vision, as if two divers swam up on either side and flashed HIDs at me
 
 
 
2) How did you recognise the event?
 I am aware through reading that visual disturbance is a precursor to an oxygen problem
 
 
 
3) What depth were you at, been to and were you diving/ surfacing etc?
 I was at 15m, had been to 81m and was on deco.
 
 
 
 4) How long had you been submerged?
90 mins approx
 
 
 
5) How much time did the scrubber have on it before the event?
 2.5 hours
 
 
 
6) What do you think caused the incident?
Current limited cells as I realised at 6m I couldn't bring the cells up to 1.6.
 
 
 
7) How was the problem resolved during the dive?
By much bodging.
 
 

 8) Have you taken any steps to ensure this doesn't happen again?
Yes. Changed the cells. Read up on cell anomalies.  Made it regular practice to perform O2 flushes and check cell performance.  Improved calibration routine.  Considering changing O2 sensor manufacturers, have written and asked for trial cells to compare performance.   Considering design/manufacture of pressurised container to test cells at high PO2, greater than ambient. Completed training course.
 
 
 
9) Any other information you feel is relevant
After highlighting this incident on the list, I have many emails from users stating that they have never been taught about current limiting and the older manuals do not make reference to it.  I feel that it is relevant that TDI and IANTD introduce Quality Control procedures to their courses to ensure that a student has to verify, at the end of their course, that they have been taught certain fundamental concepts.  Cell linearity is critical. I have an email from a user who NEVER managed to get his cells past 1.4 at 6m in a couple of years of diving the unit!!  Given the responses I have, I am surprised that more people have not died.  I think it would also be useful to go more in depth on oxygen related symptoms as this probably saved my life.