|
|
|
|
Here are the reports I've received As I get more I'll try and categorise them. But for now I'll leave them as is. I've added the only dodgy moment I've had so far as a starter
| Incident 1 | Sept 2002 | Pushing too Fast |
| Incident 2 | 22/06/2000 | Hypercapnia |
| Hanging on a boat | 1993 | Hypoxia |
| What Gas is This? | 01/09/02 | Gas Management |
| `user error' & reckless | Hypoxia | |
| Too simple | 2000 | Pre Dive checks |
| Basket Case | June 2001 | Scrubber Bypass? |
|
|
Date of Incident: September 2002
Incident Type: Pushing too Fast
Incident Description:
At 44 M on air diluent in heavy current and dark dive, Cell failure alarm sounds. Was frightened by how slowly my brain worked to analyse the situation and how long it took me to work out what was going on and that it was just a cell error and I wasn't going to die. Alarm is VERY loud at that depth and annoying
Contributing Factors:
Pushing deep dives too soon after getting unit (was my 4th to over 40m) with less than 20 dives on the unit. Narcosis
Lessons Learnt: Rebreathers bring on narcosis faster than Open circuit. Take your time on the unit
Changes: Went and did Normoxic Trimix class. Use appropriate gas for the depth now
Date of Incident: 22/06/2000
Incident Type: Hypercapnia
Incident Description:
Hypercapnia caused by breakthrough due to over packing of canister.
In June 2000 my brother (my regular inspiration buddy) and I were diving from the MV Sea Hunter filming Hammerheads at Cocos island in the Pacific. Dives were carried out using 6 place 'pangors' away from the main vessel sometimes in fairly choppy sea conditions.
The first dive of the day involved a rough 15min boat ride to the site after equipment assembly and fresh sofnalime refills on the Seahunter. We descended without incident to 35m (apart from being bussed by a huge Manta and 4m Galapagos shark and suffering a camera malfunction!) We stayed at this depth for approximately 20 minutes at which point I was aware that I was suffering from hypercapnia symptoms including disorientation, poor co-ordination and nausea. The readouts on my handsets were normal. I decided to slowly ascend whilst still on the loop and at 20m I removed the mouthpiece, closed it and experienced what can only be disguised as projectile vomiting, between breaths on my open circuit. Probably more by luck than judgment I managed to maintain a safe ascent rate and completed a couple of stops before surfacing. Because I was unable to mentally calculate my bailout deco times and knowing that the hypercapnia may very well effect these figures I carried out my 6m stops on the loop with O2 as a semi closed system. I did not have a direct O2 DV installed. I continued to vomit profusely at the surface.
from my experience on OC I know that I am particularly susceptible to Co2 build up. I felt rough for about 12hrs and did not dive again for 24hrs.
It is worth noting that during my ascent I was not co-operative with my buddy and I was very externally unaware. I put this down to the effects of hypercapnia..
Contributing Factors:
I think that the breakthrough was caused by a combination of over packing the canister and the rough boat ride prior to the dive. Because we had to take our own sofnalime I packed the last bits left in the barrel into the canister for the days diving as afterwards we would have to start using dragerzorb. The unit worked fine in breath tests an I can only assume that either the canister springs could not take the weight and got jammed during the boat journey or that channelling occurred.
We also did not know at this point that we should lubricate the canister o-rings
Lessons Learnt:
Don’t over pack the canister!
Have a backup bailout deco procedure clearly written down and carried by both parties.
Changes:
We have amended our pre-dive procedures and now check each others canister packing as a matter of course and have agreed that we can each order the other to repack if necessary.
Resolved to add an O2 direct DV.
Date of Incident: 1993 approx
Incident Type: Hypoxia
Incident Description:
I was flying my first manual unit and had been diving on the scallop grounds out of Lulworth, the dive was incident free but when I got back to the surface It was really rough and getting out of my breather to hand it into the RIB and hold on at the same time was fairly difficult in the rough seas. I spent more time trying to undo my straps than I did looking at the po2 display. When a little voice in my head said "check po2" I found it was only 12%. with the unit half on and half off it was difficult to find/press the o2 button. I couldn't take the mouthpeice out as there was no shut off and doing so would have made the breather very heavy as it filled with water.
Well fortunately I managed to get to the o2 button and raised the po2, but the big lesson I learned that day is how a bit of task loading can make you "forget" your survival skills.
Contributing Factors: rough sea conditions
Lessons Learnt: always know your po2
Changes: I have a good dose of rebreather paranoia
Date of Incident: 01/09/02
Incident Type: Gas Management
Incident Description:
During A Normoxic training session, divers where using there oxygen bottles for Trimix because they did not have special Trimix diluent cylinders. The bottles were marked and provided with good warning signs and stickers. The training went well and no problems occurred. After the training the bottles were stored and refilled for a new dive. This time the bottle was filled with 100% oxygen and put into the Inspiration rebreather. Strange was that calibration would not succeed because the handset kept calling 'Low Oxygen'. It was not understood and a second and third calibration did not solve the case. After analyzing the oxygen bottle it was found to have only 60 % of oxygen. Cause: The bottle was not emptied after being used for normoxic / trimix filling. Lesson: Do not use oxygen cylinders for any other gas!
Contributing Factors:
To little money to buy extra oxygen clean cylinders.
Not used the brains
Lessons Learnt: Do not use officially marked cylinders for other gas
Changes: Yes, will not dive with non trimix diluent cylinders anymore
My hypoxic event was `user error' & reckless'.
Incident Type: Hypoxia
Incident Description:
During pre-dive everything OK but went `battery low' prior to dive. The dive in early March 2000 was intended to get the season started & was in an inland pit with a plan to do no more than 12M. I didn't transfer Master as I should have, or more sensibly abort. Surfaced feeling dizzy after 23 min. Staying on .7 set kept a close eye on ppO2 for first half of dive, particularly with low battery alarm sounding but missed the later low O2 warning.
Changes: Since have missed several dives taking a much more responsible line when warnings given.
Too Simple a dive?
Incident Type: Failure to re-check unit after altering dive plan
Incident Description:
Shortly prior to diving with a group of mixed CC and OC people, and having done all pre-dive checks, the dive plan was changed to a shallower dive. the new plan did not require the OC bailout stages I was carrying side slung. I removed the stages and entered the water pretty well neutral. To descend it was necessary to breath out to gain sufficient negative buoyancy to get going. At 6m I stopped to do the bubble checks and had to inject diluent as there was by then zero lung volume. On attempting to inject diluent, nothing happened. By this time I needed to breathe, so I switched to my safest option of bailout to the regulator attached to the diluent cylinder. After a couple of breaths of welcome gas, I noticed that in removing the stages I had dislodged the diluent inject hose, enough that it stayed attached, but it was insufficient to pass gas. Clicked back into place, a few pushes of the dil button and I was ready to switch back to closed circuit and finish the dive. Looking back at my buddies, it amused me to see 4 octopus regulators deployed and held out to me should I have needed them.
Contributing Factors:
Late change in the dive plan.
Haste in wanting to alter the kit set up and get into the water.
Badly adjusted shraeder valve in the diluent hose fitting.
Lessons Learnt:
If you change the dive plan after the dive equipment checks, repeat the checks before getting in the water.
Adjust your buoyancy so that you don't have to run the lungs flat to get moving, you never know when you will need a breath of fresh gas!
Look around to your dive buddy, he may be better fixed at helping you than you are at helping yourself.
Changes:
Yes. The stages for bailout are checked to ensure they are not snaring on anything.
If the equipment set up is changed for any dive, equipment checks are more thorough and repeated if necessary.
Plan the dive - dive the plan.
Hi all
A couple of weeks ago I am fairly certain I had a CO2 hit. The sequence of dives were as follows;
04.06.01 - changed absorbent
05.06.01 - dive - 38m for 51mins set points 0.7/1.35 diluent 23/18 mix
11.06.01 - dive - 31m for 55mins set points 0.7/1.35 diluent 23/18 mix
12.06.01 - dive - 39m for 45mins set points 0.7/1.35 diluent air
Water temp for all dives was 13 - 14 degrees C. vis was 10m+ on last dive.
Total absorbent duration was 151 mins at the end of the last dive.
Scrubber duration prior to last dive was 106mins.
On the 3m deco stops I began to feel thick headed (No comments thank you Dave L) and felt a mild headache coming on. I also noticed some mildly erratic breathing. I had not noticed anything odd during the dive. When I attempted to climb the ladder I felt unusually weak and the Inspiration felt particularly heavy. During the rest of the afternoon and evening I felt exhausted and physically and mentally lethargic despite breathing O2 for about 10 mins.
The absorbent is from a newly purchased 20kg tub. I have not experienced any other symptoms with absorbent from this tub. The only thing I can thing of that might have shortened the absorbents life was the fact that it had been in the canister for a week. It is possible the low frequency vibrations from our boat diesel (max 900 rpm) may have settled the absorbent and caused channeling. However, this has not happened before. Alternatively damp may have affected the absorbent. The unit was dried out after each dive, re-asembled and lefty sealed.
All is well now and the problem has not re-occurred, however it was a very unpleasant experience. Has anyone else experienced a similar problem? Can anyone throw some light on this?
Notes;
After some thought I think this hit could be attributed to more than one cause.
The absorbent had been in the unit for 8 days prior to the dive. The unit had been stored on the open deck on board a live-aboard charter boat and we had experienced some heavy seas in this time. It is possible some settlement of the absorbent took place due to low frequency vibration and/or rough seas. I think it is doubtful that damp played a part since I tend to keep the loop exhausted when stored.
The basket "O" ring was probably not well enough lubricated and possibly let some CO2 bypass the scrubber.
Remedies
I take very good care to make sure the "O" ring is well lubricated and the basket is free to move up and down in the scrubber canister.
When ever the absorbent is left in the scrubber and on the boat for longer than a couple of days without use I change it regardless of duration.
I tend to be very conservative on changing the absorbent these days, often changing the sorb inside the 3 hours max. and every dive if deep.
I have not had a second hit since
|
|