What is your IWR Kit Comprised of?

[tbone1004]

@mmadiver if you are not a cave diver, you will likely not see dedicated O2 rebreathers for decompression. They are not uncommon in cave country because the dive lengths can easily exceed the scrubber duration of even the biggest scrubbers. The KUR is regularly doing 12+ hour dives and those require either a second CCR or a mountain of OC gas since most of that time is obviously decompression.

25 minutes on a pure O2 rebreather, with a proper purge, while swimming, and without doing any flush could cause a hypoxic condition. The difference here is that in IWR, you are not moving, i.e. not consuming much O2, and you have to go back to some sort of diluent gas for "air breaks" every 15-20 minutes depending on which method you subscribe to. You can't consume enough O2 to go hypoxic in those conditions since each time you switch back from the "air break" you would do a flush.

 

[MichaelMc]

Thank you for this discussion! I had wondered about inert gas build up in the emergency/prophylactic deco procedure of 'surface, grab the O2 rebreather, and go back down'. It had not seemed discussed as something that procedures were preventing. I had not thought about air breaks. Though, diving the rig blind, a timer for those breaks would seem very important, maybe, for going hypoxic, depending on the rig you are using.

 

[Michael Guerrero]

A tender is important.

 

[Akimbo]

25 minutes on a pure O2 rebreather, with a proper purge, while swimming, and without doing any flush could cause a hypoxic condition.

Recreational divers should have no hesitation to blow off some gas (purge the bag or the mask) to minimize diluent in the bag. A rig designed for IWR or decompression should have much larger O2 cylinders and/or be surface supplied compared to rigs designed for combat swimmers.

 

[tbone1004]

Recreational divers should have no hesitation to blow off some gas (purge the bag or the mask) to minimize diluent in the bag. A rig designed for IWR or decompression should have much larger O2 cylinders and/or be surface supplied compared to rigs designed for combat swimmers.

Unsure how or why we got to comparing O2 rebreathers without monitors for our purposes vs. the combat swimmers other than the fact that the units can be the same, but whatever.

in cave country, the O2 breathers typically don't have any "onboard" tanks, it's all done offboard. So you have the scrubber/lung/loop and you plug in typically with a bc inflator for offboard gas. You will typically have to do an O2 flush when you come back from your air breaks if you do air breaks on OC, so it's never an issue.

 

[Akimbo]

Unsure how or why we got to comparing O2 rebreathers without monitors for our purposes vs. the combat swimmers other than the fact that the units can be the same, but whatever.

Are there any pure O2 rebreathers that aren't primarily made for combat swimmers? Maybe it's just semantics but I never considered mixed gas eCCR an O2 rebreather. All the pure Oxygen units I'm familiar with are dumb -- no electronics, sensors, batteries, etc.

I think the issue came up because I mentioned that I have made them for use in chambers and underwater in remote locations where Oxygen availability was very limited and/or expensive.

 

[kelemvor]

Are there any pure O2 rebreathers that aren't primarily made for combat swimmers? Maybe it's just semantics but I never considered mixed gas eCCR an O2 rebreather. All the pure Oxygen units I'm familiar with are dumb -- no electronics, sensors, batteries, etc.

I think the issue came up because I mentioned that I have made them for use in chambers and underwater in remote locations where Oxygen availability was very limited and/or expensive.

Have you ever considered using medical oxygen generators? They can be purchased for under $1,000USD and the ones I've seen operate on regular 110/220vac. If you have considered but abandoned the idea, what was your reasoning?

 

[Akimbo]

Have you ever considered using medical oxygen generators?

We looked at them. These projects were on vessels of opportunity and most of the gear was leased. The inexpensive generators didn't offer the reliability the client was looking for. This was 12-15 years ago. These projects probably wouldn't use divers at all today since ROVs have become so plentiful and relatively inexpensive. I only brought it up since recreational expedition divers are faced with similar logistics problems and even more limited budgets.

 

[tbone1004]

@Akimbo while I don't know of any specifically marketing them as O2 rebreathers, you can order several as "blank" rebreathers and use them for O2 only. I.e. kiss sidekick would actually be a decent O2 rebreather

@kelemvor the o2 generators really shouldn't be used inside of a chamber because of the electric motors. If you want one to fully allow a person to breathe true high levels of oxygen, you actually need to run a pair of them in tandem. The biggest size you are really going to see is about 10lpm which is about .35cfm. They do that so you don't oxtox during continuous use which is what these are intended for. Most of the ones you find are 5lpm, so if you wanted to use these for surface O2, you'd really need a pair of them running together to get someone breathing close to 100% O2.

 

[Akimbo]

Akimbo while I don't know of any specifically marketing them as O2 rebreathers, you can order several as "blank" rebreathers and use them for O2 only. I.e. kiss sidekick would actually be a decent O2 rebreather

Thanks, for the info. You can also buy pure O2 Dräger Lar Vs and several units that are sold for mine safety that are easily modified to work underwater. We got a bunch of old Perelli rebreathers and modified the gas manifold for an LP surface-supply for Oxygen.