High PO2 near miss

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doctormike

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Not sure if this should be posted here or in the rebreather forum, but since it's a near miss and a lesson learned, I put it here. This was just posted on YouTube, and mentioned on another dive forum:


I don't dive a Meg, but I was wondering about how that happened without notice. It's not clear from the video whether the diver eventually noticed the high PO2 or if the person filming him saw it and alerted him. I couldn't see the front of his HUD, but I was wondering why his HUD didn't alert him? The guy who posted the video mentioned in the comments that it might have been the video lights. I was wondering if the fact that he missed the alarm could have been the result of the HUD design or just diver inattentiveness?

I like the JJ HUD - a light for each sensor, and the code flashes red for alert values above 1.6 or below 0.4. There is also a buddy warning light on the end of the HUD, so if it's flashing an alert value to the , the end (visible to other divers) is also flashing.

Looking at the Meg HUD simulator, it looks like it flashes red for low and green for high alerts. Maybe this website simulates older software or hardware? It does seems potentially confusing - it flashes red for 0.7 and green for 1.8? I guess it's a design choice that you can get used to, but in this case it looks like it didn't work, for whatever reason. People seem to love Megs, and it looks like a well designed unit, just wondering about this...

I switched to a NERD myself, but the JJ HUD is still a good backup.
 
geez, scary. makes me glad for an mccr.
 
as a non rebreather diver would this have been constantly added volume to the counter lung and been noticeable by the change in buoyancy?
 
Two observations that I made (also as a non-CCR diver)..

1. His computers appeared to be mounted in a sub-optimal way. This is very obvious at the point where the camera picks it up. The diver has both arms in a natural relaxed position, and his computers are pointing away from him. I orient my computer so it is on the inside of my forearm, so when my arms are relaxed the screen is facing towards me, not away from me. Yes, his HUD should have warned him too...

2. He didn't see to be particularly aware and comfortable in the water. Especially at the stop, hanging vertically, grabbing onto the anchor line with his legs? Yes, he was probably out of sorts and task loaded, but still.... Also, hanging onto his BO 2nd stage? Is that standard protocol? I would've thought the preference would be to clip it off?

Neither of these observations may have anything to do with why this all occurred, but IMO they speak volumes to his general comfort, experience and situational awareness..
 
1. His computers appeared to be mounted in a sub-optimal way. This is very obvious at the point where the camera picks it up. The diver has both arms in a natural relaxed position, and his computers are pointing away from him. I orient my computer so it is on the inside of my forearm, so when my arms are relaxed the screen is facing towards me, not away from me. Yes, his HUD should have warned him too...

I don't know about that, it seems pretty standard to me. When swimming in the standard "superman" pose that is taught by some agencies (horizontal trim, arms out in front, head up), the computer in this orientation would be more visible than if it was on the inside of his forearms.
 
Are there not audible alarms on the Shearwater for high or low po2?

No the Shearwater does not nor should it as I do not want my unit talking to me. Some units do have audible and vibration and I do not know this unit. It is the responsibility of the CCR diver to KNOW their PPO at all times. Not only did he not check his computer, his HUD - he also did not listen to the solenoid or the MAV. He did not get to a PPO2 of nearly 2.5 instantly. Many units have a flow restrictor on the O2 reg so it can take a little effort. He should definitely had some warning beyond the computer. An aware CCR diver will have already taken corrective actions before the PPO2 got anywhere near this high.

There is a possibility that he had bailed out at a lower PPO2 (why not dil flush instead if it was that bad?) and it continued to rise because the loop content was not equalized. That high of a PPO2 is not 'dangerous' immediately. The diver would have had time to lower it if they had been observant.
 
I switched to a NERD myself, but the JJ HUD is still a good backup.

I use the NERD myself. I like having the second computer connected to my CCR DiveCAN. During a dive, it is my primary computer with my wrist being secondary. Seeing this guy at PPO2 of 2.5, I bet I cross check my wrist more then he checked his primary. The one complaint I had on the NERD was SW's mounting bracket for the Prism 2. It was the cloth strap. I know the JJ has a rigid bracket. I ended up printing one for my unit which works very well.
 
https://www.shearwater.com/products/teric/

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