First Rebreather - Used Prism 2 - Good Instructor - Is it OK ?

[grantctobin]

Switch to OC mode is easier and faster with BOV. It also helps if you need to take a few sanity breaths in case of CO2 hit. Other than that using OC reg is more convenient way to bailout especially in case of switching gases for deco. Also all my BO regs are more comfortable to breath than my Hollis BOV but you milage may very

The theory being that those “sanity breaths” in the event of a proper CO2 hit aren’t going to do anything to relax you. You’d be lucky to be sufficiently mentally cognizant to not kill yourself by the time you finish off a 2L/3L/4L, especially at any significant depth. Don’t plumb BOV into tanks that small. If that’s your plan, you’re better off with a DSV.

 

[vitaly]

Don’t plumb BOV into tanks that small. If that’s your plan, you’re better off with a DSV.

I can be wrong about sanity breaths. Never had CO2 hit and hope won't have it in the future. My point is different. I'd like to stick with the approach which works for any dives I do (air, normoxic, hypoxic). My BOV is connected to offboard tank and even I think that it adds some safety I still treat it more like DSV and switching to OC reg ASAP in case of bailout. It's also a clear sign for everyone in my team that I bailout and follow OC ascent protocol like switching gas at specific depth.

 

[houdini0118]

Good luck. You got the right electronics for that unit. Mine is basically the same and i got it year. I haven't touched my OC gear since except to jack the regs for bailouts. You will love diving this unit. Just be super careful especially if you have a lot of experience with open circuit as the dangers are different and overconfidence can go bad fast. The biggest issue i have seen is people that only dive them a few times a year sometimes go and do something boneheadly stupid. If you dive it a few times a month you will do a lot better.

 

[jfe]

...................

Also - I went ahead and ordered the BOV for the unit. What's the best way to plumb it to DIL - should I go straight to offboard and maintain a backup second stage for redundancy? While i'm a long way off from taking the MOD 3 class, when that time comes do most get some sort of splitter or switch that lets you change the BOV feed from normoxic to hypoxic bailout?..........................

I dive the P2 and changed back from a BOV to DSV, personal choice due to weight and hose routing I didn't like. When you get the BOV there are clear hose routing instructions. you do not need a switch block or whatever. The 1st stage setup allows you to take the OPV out as the BOV regulator acts as the OPV, setup is straight forward.

 

[stuartv]

The theory being that those “sanity breaths” in the event of a proper CO2 hit aren’t going to do anything to relax you. You’d be lucky to be sufficiently mentally cognizant to not kill yourself by the time you finish off a 2L/3L/4L, especially at any significant depth. Don’t plumb BOV into tanks that small. If that’s your plan, you’re better off with a DSV.

I am not sure I understand what you're saying.

It sounds like you are saying that if you have a CO2 hit, switching your BOV over to a small inboard tank would not do anything to help you and you probably wouldn't be able to then switch to an OC reg on an offboard bailout before you completely killed the onboard small tank.

So, (you're saying) it would be better to not have the BOV at all.

If switching the BOV over to a small onboard tank doesn't help at all and you still couldn't switch to an offboard OC reg, how would you be able to switch to an offboard OC reg directly from the loop full of CO2? That sounds kind of like saying "a gas tank in your car that only has 1 quarter of a gallon (or 1 liter) for Reserve fuel capacity is not going to make any real difference in getting you to a gas station, so it would be better to not have the Reserve capacity at all."

 

[rjack321]

I am not sure I understand what you're saying.

It sounds like you are saying that if you have a CO2 hit, switching your BOV over to a small inboard tank would not do anything to help you and you probably wouldn't be able to then switch to an OC reg on an offboard bailout before you completely killed the onboard small tank.

So, (you're saying) it would be better to not have the BOV at all.

If switching the BOV over to a small onboard tank doesn't help at all and you still couldn't switch to an offboard OC reg, how would you be able to switch to an offboard OC reg directly from the loop full of CO2? That sounds kind of like saying "a gas tank in your car that only has 1 quarter of a gallon (or 1 liter) for Reserve fuel capacity is not going to make any real difference in getting you to a gas station, so it would be better to not have the Reserve capacity at all."

If you have a BOV then plug it into a proper sized offboard tank (unless you are doing the backmounted 50s thing)

If you have a DSV then you have already discounted the risk of a CO2 hit. Even if its a low-ish priority keep the BO 2nd stage handy - like on a necklace not stowed on the BO tank.

Worst case is to plumb in the BOV to a onboard 2 or 3L cause you'll drain that before you have any recovery and now you're OOA on top of having a CO2 hit. Plus its very common to use hypoxic dil on more modest dives. 10/50 is practically a standard dil in many places - and 3L of it is a terrible gas/volume to plumb into your BOV.

 

[vitaly]

Worst case is to plumb in the BOV to a onboard 2 or 3L

It's default factory P2 + BOV configuration and it works OK for air dill and air depths. Hypoxic dive is a different story.

 

[rjack321]

It's default factory P2 + BOV configuration and it works OK for air dill and air depths. Hypoxic dive is a different story.

Default factory means nothing.
Its a terrible choice and why would you use one configuration with air dil and another at deeper depth. Plug your BOV into sufficient volume so its not a mere "transition"

ps if you do drain the 3L with a BOV guess what you just did to your wing gas? Yup not only are you OOA but you're stuck orally inflating too.

 

[vitaly]

Default factory means nothing

For me it means it won't kill you if you start your initial training/practice this way.

Its a terrible choice and why would you use one configuration with air dil and another at deeper depth.

I don't but some people just don't dive deep. Also in TDI you need to get at least 50 hours before taking normoxic training. For me it took about a year.

ps if you do drain the 3L with a BOV guess what you just did to your wing gas? Yup not only are you OOA but you're stuck orally inflating too.

I don't need to inflate my wings on ascent. Only at surface and I dive drysuit

Anyway as I mentioned above my BOV is plugged to off-board but I don't think it's wrong to plug it to onboard 3L on air depth dives. It's not the best choice but definitely not terrible one

 

[rjack321]

I don't need to inflate my wings on ascent. Only at surface and I dive drysuit

You are comparing this bailed out OOA on your BOV ascent to your "normal" practices. This now bailed out dive has already gone massively sideways.

You have a CO2 hit and switch to BOV
Breathing like a freight train you drain the 3L in a minute at depth while you're narced out of your mind
****!!!!! now you are OOA
You fumble switching to your stowed 2nd stage (while gasping)
Don't get the loop fully closed in your fumbling
CCR is now flooded or partially flooded
Heavier than usual, you are stuck orally inflating and you are still on the offboard BO gas anyway

Vs
Switch to BOV plugged into a suitably sized offboard BO
Use the remainder of your 3L as wing gas for your ascent
No risk of OOA or panic switching to another gas source. (edit: if the CO2 was bad enough its almost impossible to carry enough OC gas to calm down before using up even a full 80)
Start your ascent sooner instead of spending all your bandwidth switching twice.

Using an onboard 2 or 3L tank as your BOV source is a mistake which opens up a whole lot of other potential problems you just don't need on an already bad day.