Video about oxygen shutoffs on Sidewinder

[rddvet]

It's an interesting video, but it doesn't mimic the facts related to the death in Ginnie which has led to many questioning the safety of having an oxygen shutoff. I'm pretty sure the diver who died was on hypoxic trimix. I see what they're going for, but it doesn't convince me an oxygen shutoff is safe. Edd also has a ridiculous sac rate and is more comfortable in the water than 99.99999999% of divers.
I've heard some rumors that there's a handful of sw instructors who are pissed hearing that some question the safety of having an inline shutoff on the oxygen. This seems to fit with those rumors.
Seems like a good video to open up a discussion on though if nothing else. Personally I'm not a fan of an inline oxygen shutoff.

 

[Jack Hammer]

41min video, I'll have to watch it later. Inline shutoff on the O2 line is an accident waiting to happen, especially in a cave or confined area, IMO. The only "upside" I see is in the rare instance where you are unable to reach the valve and need to stop flow. The downsides including accidentally closing it outweigh that by a very long shot.

 

[kelemvor]

I think it's one of those things you can get away with...until that one time when you can't.

 

[tbone1004]

I use one, it doesn't bother me. I haven't watched the video but the premise is sound, IF and only IF you are running min-loop volume at the time the O2 turns off. With my sidemount unit I have to be very careful to pay attention to this because my O2 sphere is prone to rolling off in certain restrictions. You can also hang out at a flat depth and maintain a ppO2 this way without looking at a monitor. The big variable though is that you must be at min-loop volume to do it. If you are running larger loop volumes then you do have a risk of going hypoxic. The deeper you are the more pronounced the effect is as well because there is that much more mass of O2, so if you are pretty shallow the difference in loop volume is fairly small.

I think the shutoff on the Sidewinder is OK because of where the O2 bottle is located and how difficult it can be to reach back to the valve itself if you have top mounted stages and if you are hot dropping with a rich dil then you may want to cut the leaky valve off for descent and it's a convenience. Like anything though it has risks and you have to weigh the risk vs convenience factor. I wouldn't put them on most units and if you have a needle valve it can provide the same function, but I think this is one of those gray areas that needs to be acknowledged where there isn't a universal decision that can be made as these rigs are still very new and continuously evolving.

 

[davehicks]

The gist of the video is that if your O2 is OFF, moving at a steady depth, you can't breathe the loop to hypoxic levels unaware. After 8-10 minutes the reduction in loop volume from CO2 removal is so much that the ADV kicks in. If your ADV is off then you will very noticeably feel the lack of volume and need to take action. It's not realistically possible to go hypoxic on a KISS unit (at steady depth) without warning.

 

[Wibble]

Inline shutoff on the O2 line is an accident waiting to happen, especially in a cave or confined area, IMO.
...
The downsides including accidentally closing it outweigh that by a very long shot.

I don't wish to be trite, but isn't Rebreather 101's slogan "always know your PPO2"?

Meaning you monitor this with your HUD / Nerd and notice if the PPO2 drops as alarms go off. As it's a manual CCR you'll be well aware of monitoring everything.

(Happy if I'm wrong with this assumption)

 

[Jack Hammer]

I don't wish to be trite, but isn't Rebreather 101's slogan "always know your PPO2"?

Meaning you monitor this with your HUD / Nerd and notice if the PPO2 drops as alarms go off. As it's a manual CCR you'll be well aware of monitoring everything.

(Happy if I'm wrong with this assumption)

Not trite at all. I'm in full agreement that one 'should' always know their PO2 and 'should' catch a declining PO2 long before it becomes an issue. The reality is some folks become complacent over time and don't monitor stuff as often as they should. This becomes magnified when task loaded.

To me an inline O2 shutoff is simply another potential failure point and 'potential' way to inadvertently stop your O2 flow while only offering limited benefit in very specific scenarios. That said, people are free to use them if they feel differently and someone having one wouldn't preclude me from diving with them.

 

[rddvet]

41min video, I'll have to watch it later. Inline shutoff on the O2 line is an accident waiting to happen, especially in a cave or confined area, IMO. The only "upside" I see is in the rare instance where you are unable to reach the valve and need to stop flow. The downsides including accidentally closing it outweigh that by a very long shot.

I tend to agree with you. And more importantly, if you're not running hypoxic dil and you lose your oxygen who cares? Your dil is likely going to be at p02 that is safe to add and still have enough oxygen content.
My issue is that I'm pretty sure this is directly a response to the talk of the negatives of shutoffs due to the Ginnie death. If you're trying to prove that point, do it with hypoxic dil. The video is comparing apples and oranges imo if the intent was to quell the post-death talk that's been happening.

 

[kensuf]

Don't forget, even if you're running min-loop, if you ascend a little bit and make no other changes, you're no longer running min-loop. And you'll also get a PO2 drop.

I can show you a video of some guy named Leon cutting up a Meg while diving too.

 

[rjack321]

The gist of the video is that if your O2 is OFF, moving at a steady depth, you can't breathe the loop to hypoxic levels unaware. After 8-10 minutes the reduction in loop volume from CO2 removal is so much that the ADV kicks in. If your ADV is off then you will very noticeably feel the lack of volume and need to take action. It's not realistically possible to go hypoxic on a KISS unit (at steady depth) without warning.

Yes you can.
Swim at 30ft with air dil and O2 off. After about the 2nd or 3rd ADV injection you'll be going hypoxic quick.