First Rebreather Questions

[rjack321]

Have you tried it? A haptic alert is noticed no mater what position, task, or visibility conditions exist.

Whenever someone says "always", "no matter what", etc I know they don't have a good grasp of the spectrum of mistakes and omissions which can and sometimes do happen with tragic consequences.

 

[rddvet]

I think a HUD should be a requirement for a new diver. Just a better way to make sure if you get task loaded you dont have a p02 issue. I personally will never dive a unit without one. I have the fathom programmed narced at 90 hud that came on my version one fathom. My wifes died and she got the new fathom. New fathom is definitely better, but I still prefer the narced at 90 because I have alot of hours behind it.
I also think a BOV should be standard. I've never actually had to use it in an emergency but have taken a few sanity breaths and I love the easy quick access. One underlooked pro of the bov is help with things like reverses. This may be very specific to me because I have horrific allergies. I find on cc I get much more stuffiness and congestion movement than oc (which makes sense from a physics standpoint). When I'm really having issues, I just quickly switch to oc and it gives me some relief. Most recently I was exiting a cave (Taj Maha in mexico) that comes from about 30-40 up to 8 feet then back down (room of reflections). I got a horrible reverse due to a cold I'd had a few weeks prior. I kept going back deeper and clearing and attempting to continue my exit. After a few minutes of trying, I switched to oc as I could feel pressure building and the pressure immediately released, I got over the hump and back down to 30 ft of water and went back to closed circuit.
I have the divesoft bov. I've dove the golem as well. I personally prefer the divesoft, but around here golem is seen way more commonly than divesoft.

 

[rjack321]

I think a HUD should be a requirement for a new diver. Just a better way to make sure if you get task loaded you dont have a p02 issue. I personally will never dive a unit without one. I have the fathom programmed narced at 90 hud that came on my version one fathom. My wifes died and she got the new fathom. New fathom is definitely better, but I still prefer the narced at 90 because I have alot of hours behind it.
I also think a BOV should be standard. I've never actually had to use it in an emergency but have taken a few sanity breaths and I love the easy quick access. One underlooked pro of the bov is help with things like reverses. This may be very specific to me because I have horrific allergies. I find on cc I get much more stuffiness and congestion movement than oc (which makes sense from a physics standpoint). When I'm really having issues, I just quickly switch to oc and it gives me some relief. Most recently I was exiting a cave (Taj Maha in mexico) that comes from about 30-40 up to 8 feet then back down (room of reflections). I got a horrible reverse due to a cold I'd had a few weeks prior. I kept going back deeper and clearing and attempting to continue my exit. After a few minutes of trying, I switched to oc as I could feel pressure building and the pressure immediately released, I got over the hump and back down to 30 ft of water and went back to closed circuit.
I have the divesoft bov. I've dove the golem as well. I personally prefer the divesoft, but around here golem is seen way more commonly than divesoft.

The other potentially huge benefit of a BOV is if you are delirious, in and out of consciousness, bad gas, CO2, hyperoxic, hypoxic or any other reason... your buddy can switch you to your BO. You'll probably drown if they attempt that with a DSV. If they are an OC buddy switching a BOV is simple enough. An OC buddy successfully executing a dil flush is far less plausible. Let's face it, your 3 min how to do a CCR dil flush briefing on the boat is not going to be retained when they see you losing consciousness at depth.

Ideally, you'd have a gag strap to facilitate retaining the BOV as well - they save lives.

 

[davehicks]

Whenever someone says "always", "no matter what", etc I know they don't have a good grasp of the spectrum of mistakes and omissions which can and sometimes do happen with tragic consequences.

Don't be pedantic. The point is that there is more than one way to alert the diver. Haptic or Hud, they are both fallbacks for proper attention and discipline in monitoring your PPO2 display.

 

[broncobowsher]

The HUD is a warning to look at your hand controller -The nerd is more than just a HUD with smithers code though - you have more info regard to PO2 depth and time and deco obligation - a back up computer - I use my nerd info more than my controller - especially when Im fluffing around with tank, gear etc and my hand is busy

I also look at the NERD more than the controller.
For Shearwater products, if you see RED something is wrong. There is no red in the regular display. Once something goes wrong, there is a lot of red. It gets your attention with it in your eye.

That whole "the surface is the most dangerous place for a rebreather" nearly got me once. Going through my checklist and got stopped after the ADV check but before O2 turn on (now corrected by putting them back to back). Fussing with a disconnected drysuit hose while on the loop standing in waist deep water (hot outside and trying to prevent overheating at the surface). Why is the NERD all red, I'm not even diving? PPO2 0.10 and it was not happy. Nice to have a display in your face. Carefully remove the DSV and take a few breaths of air and figure what just happened. Go make a new checklist. Would not have seen that on a handset, the hands were busy with an unhappy drysuit hose that was fighting me way too much that day. Maybe a blinky light would have worked, not sure I would have seen it in full sun.

I also like the reality check that both computers are nearly the same at the end of the dive. And the backup computer has cell data from the dive, so it has a better idea what is going on instead of a fixed setpoint backup computer.

 

[Wibble]

Would you please elaborate when the DSV+necklace was more convenient for you than the BOV? Outside of scootering, nothing comes to mind, but I've also never used a DSV.

Several reasons…

• A BOV needs a “hard” LP hose connected to your bailout — NOT your diluent— and this hose needs to be connected using a sealed wet connector like a QC6. You still end a normal regulator and also a standard Schroeder/BCD connector, i.e. three LP hoses that point downwards, something like a Tec3 first stage.

• The BOV hose has to be routed correctly such that the stage cylinder can be unclipped and swung forwards to re-stow hoses, etc.

• The BOV hose will generally be attached to your loop hose on the LHS (bottom bailout) using either a hose wrap or bungees. This is heavy, drags and unbalances your loop, makes it harder to turn your head and it often pulls on your mouthpiece, basically it messes with your loop especially if moving your head when looking around.

• A BOV is never as good as a decent second stage regulator especially when deep.

• A BOV is a single point of failure especially at a point where you’re in the sh!t. I’d prefer a clean reliable reg for a caustic (which I’ve had) and a different reg has a different mouthpiece.

• When diving with a hypoxic bailout, you still need to bailout to a rich mix, i.e. another decompression bailout with a standard reg. if your muscle memory is to flick the BOV switch, you’re breathing a hypoxic mix.

• BOVs are a lazy option and I found I became apprehensive about switching my loop for a bailout underwater. Sure, this is just me being lazy, but it was my main reason for reverting from the BOV back to the DSV.

• The major selling point of a BOV is for the ubiquitous CO2 hit. I’d sooner have the quality regulator to breathe like a steam train from than a BOV.

• You need to keep practicing switching bailouts. A BOV isn’t the panacea.

• By having a necklaced quality second stage regulator under your chin, there’s no issues with swapping over for a “sanity breath” (i.e. no reg hoses to tidy up). The necklaced reg is on a long hose and can be easily donated: pull out your reg from the necklace and shove into the mouth of the gasless diver, then come off your loop and flip the hose over your neck and back on the loop for them to have some space. Then unclip your bailout and give it to them as you both get the heck out of Dodge.

All of those are minor things but they total up to an embuggerance.

 

[Wibble]

Have you tried it? A haptic alert is noticed no mater what position, task, or visibility conditions exist. Even with a hud the first thing you do after an alert is look at the actual computer. So i feel that is a non issue.

I dive with two computers but only one has PPO2 readouts. If that fails I end my dive. Now if I did dives that did not enable an immediate exist to the surface I would get a Nerd or similar.

I’ve a Petrel 2 and a Nerd 2. I’d definitely be wary of diving without something in my face as it isn’t just for alerts, it is for constant monitoring.

Let’s face it, a haptic alert is like being slapped around the face with a fish for not monitoring your system. (Cue Monty Python fish slapping dance)

 

[lermontov]

Several reasons…

I remember about three years ago you argued strenuously for the BOV- you primary reason was a co2 hit

the rest of your above reasons are not game changers esp if your switching back to OC on a regular basis ( eg cave diving) honestly the arguments you present against id classify as secondary and are a non issue compared to the immediate threats/benefits @rjack321 outlined in his post.

im sure youve got enough mileage behind you to switch between configurations without too much angst

 

[Wibble]

I remember about three years ago you argued strenuously for the BOV- you primary reason was a co2 hit

the rest of your above reasons are not game changers esp if your switching back to OC on a regular basis ( eg cave diving) honestly the arguments you present against id classify as secondary and are a non issue compared to the immediate threats/benefits @rjack321 outlined in his post.

im sure youve got enough mileage behind you to switch between configurations without too much angst

Absolutely.

My preference, based upon my experience, is for a necklaced regulator. Am not denigrating the BOV, just have a lot of personal reasons for preferring the necklaced bailout reg.

Funny how more experience affects one’s preferences

 

[inquis]

Several reasons…

Thanks so much for those thoughts. I hadn't conceived of many of them, likely because I run a dilout system (Fathom) and wouldn't be handing off BO bottles. They make a lot of sense for your particular setup, so I definitely agree that our experience colors our preferences.