Please explain DIR to me...

[RichLockyer]

Seems to me te OOa diver might have to retrieve the reg on his own if he wants to be sure he's gong to make it home.

"Seeing" would make little difference in a restriction that tight.

If he's dropped the reg and not immediately stopped, then the reg is going to be beneath me, or in zero-viz, maybe even behind me. If he did immediately stop (I sure would) then it's going to be under him, probably in the chest or upper leg area, depending on how high above the bottom he is.

Let's ignore zero-viz, because color would not matter... so assuming limited to open viz... the reg will be in front of me and somewhere under him.
I'm not going to WAIT for him to search for it. I'm going to reach forward, grab it, and shove it into his hand, or against his abdomen or chest (however far forward I can reach), while tapping the purge button to clear ot of any dirt AND to provide an audible signal.

Basic procedures do not change. You follow the same basic procedures during clear-water diving as you do in a lights-out or silted out zero-viz situation. If you develop methods that require certain senses, or certain equipment, to be functional, then you're neck deep in dung when one of those items fails.

You can use a brightly colored regulator if you want to, or you can use a black one.
Nobody is going to tell you that you can't.

 

[filtered]

Always go to a working source. If your deco bottle goes south, you don't futz around with your back gas, you go to a working source - your buddy. You always have the same response to the problem.

Once you have gas, you can futz around with things like swaping regs and crap.

How would swapping regs help if the diver has lost the deco gas?

I was thinking along the lines of rather than sharing gas, which is an additional task-loading, would'nt it be simpler to switch to backgas, and modify the deco schedule accordingly ? Seems simpler than swapping regs.

 

[RichLockyer]

How would swapping regs help if the diver has lost the deco gas?

I was thinking along the lines of rather than sharing gas, which is an additional task-loading, would'nt it be simpler to switch to backgas, and modify the deco schedule accordingly ? Seems simpler than swapping regs.

If the failure is merely a blown reg, then there's no need to modify the deco schedule, which would not be a good option on a long dive where you may already have an hour to hang... and certainly not in any event if your backgas is something like 10/70.
From a boat, surface conditions can change quickly and dramatically... it would be unwise to extend your deco by even an hour in OW.

You follow your basic training. You get gas from your buddy, because you know it works. It also puts him on notice that the stuff has just hit the fan. That gives you time to sort out what the most correct resolution is, be it BB the deco gas, modding the deco schedule and going to backgas, or swapping out regs and holding to the schedule.

 

[filtered]

If the failure is merely a blown reg, then there's no need to modify the deco schedule, which would not be a good option on a long dive where you may already have an hour to hang... and certainly not in any event if your backgas is something like 10/70.
From a boat, surface conditions can change quickly and dramatically... it would be unwise to extend your deco by even an hour in OW.

You follow your basic training. You get gas from your buddy, because you know it works. It also puts him on notice that the stuff has just hit the fan. That gives you time to sort out what the most correct resolution is, be it BB the deco gas, modding the deco schedule and going to backgas, or swapping out regs and holding to the schedule.

Ok. To get a clearer picture, let us assume a dive to 45 m on 21/35, with a single deco gas of EAN50. Bottom time 20 mins.

Assuming the diver lost all the deco gas because he forgot to shut the valve properly on his deco bottle and it freeflowed out. When it comes to the 21 m gas switch, he would realise that he is out of gas. He goes over to teammate who donates the stage reg initially to sort things out, and donor goes to backup. Once things are calm, OOA diver will revert to backgas. All team members will do modified deco schedule. Although we carry 1.5 times the deco gas required, I don't think it would be enough for 2 divers to deco with.

I suppose for a dive that requires 10/70 bottom mix, would also use 35/25, EAN50 and Oxygen for deco. Perhaps also a 21/35. I guess chances of losing all these deco gasses is pretty slim.

 

[RichLockyer]

backup. Once things are calm, OOA diver will revert to backgas. All team members will do modified deco schedule. Although we carry 1.5 times the deco gas required, I don't think it would be enough for 2 divers to deco with.

Or... you proceed to share, all team members participate in the sharing, and go as long as possible, upon which everyone goes back to backgas and does a modified deco schedule... for the example offered, probably a very common profile, decompressing on 21/35 would add about 40 minutes to the deco time if it were done completely on 21/35. I certainly would not want to risk the added exposure, but I also would not leave a team member hanging.
I'm thinking that the most common cause of a loss of deco gas is a failed reg and not an actual gas loss... those with more experience, feel free to confirm or deny.

I suppose for a dive that requires 10/70 bottom mix, would also use 35/25, EAN50 and Oxygen for deco. Perhaps also a 21/35. I guess chances of losing all these deco gasses is pretty slim.

True, as would the likelyhood of a loss of deco gas as described above. I can't imagine that the diver or a team member would not notice the deco gas streaming out of a reg... at least not in OW. Perhaps in a cave where you're dropping the deco gasses and someone's propwash or an errant fin throws a reg into freeflow. Of course in the cave, you have the luxury of being able to extend deco without having to worry about surface conditions.

 

[Reinoud]

Or... you proceed to share, all team members participate in the sharing, and go as long as possible, upon which everyone goes back to backgas and does a modified deco schedule... for the example offered, probably a very common profile, decompressing on 21/35 would add about 40 minutes to the deco time if it were done completely on 21/35. I certainly would not want to risk the added exposure, but I also would not leave a team member hanging.
I'm thinking that the most common cause of a loss of deco gas is a failed reg and not an actual gas loss... those with more experience, feel free to confirm or deny.

True, as would the likelyhood of a loss of deco gas as described above. I can't imagine that the diver or a team member would not notice the deco gas streaming out of a reg... at least not in OW. Perhaps in a cave where you're dropping the deco gasses and someone's propwash or an errant fin throws a reg into freeflow. Of course in the cave, you have the luxury of being able to extend deco without having to worry about surface conditions.

I understood that deco bottles and stages are turned off when not in use (but with the regulator under pressure). When you start using them, you put the regulator in your mouth, double check that it is the correct bottle, look at the gauge and take a breath. When you see the gauge go back you are sure that that is the bottle you are breathing from and open the valve.

So loosing gas should not be an issue IMHO

(but I've never used a stage or deco bottle yet, so this information is only from the Internet and not from an instructor)

 

[filtered]

I understood that deco bottles and stages are turned off when not in use (but with the regulator under pressure). When you start using them, you put the regulator in your mouth, double check that it is the correct bottle, look at the gauge and take a breath. When you see the gauge go back you are sure that that is the bottle you are breathing from and open the valve.

So loosing gas should not be an issue IMHO

(but I've never used a stage or deco bottle yet, so this information is only from the Internet and not from an instructor)

yes the hoses are supposed to be pressurised and valves turned off. However, for ocean diving, two of the most possible ways to lose deco gas is

1) valve was not shut off properly and gas was freeflowing out. This could be a very real possibility, especially if scootering, and in the situations where it is not possible for the divers to be wing on wing, so might fail to notice.

2) regulator failure.

For a 45 m dive, with 21/35 backgas and EAN50 deco gas, the deco is pretty straightforward. Losing the EAN50 would'nt add 40 mins to the deco time, it would just double the deco time if done on backgas.

 

[RichLockyer]

For a 45 m dive, with 21/35 backgas and EAN50 deco gas, the deco is pretty straightforward. Losing the EAN50 would'nt add 40 mins to the deco time, it would just double the deco time if done on backgas.

What profiles are you running? My 40 minute figure (actually 37) was from Vplanner. Total runtime of 84 vs 47 minutes for a 20 minute bottom time with conservatism +4. Backing down to +2 it's a 22 minute difference.

 

[filtered]

What profiles are you running? My 40 minute figure (actually 37) was from Vplanner. Total runtime of 84 vs 47 minutes for a 20 minute bottom time with conservatism +4. Backing down to +2 it's a 22 minute difference.

I'm basing on a profile of 45 m with 20 mins bottom time, with 21/35 backgas and EAN50 deco gas.

With no failures, I will have a total runtime of 48 mins

With loss of EAN50, total runtime will increase to 68 mins.

 

[RichLockyer]

I'm basing on a profile of 45 m with 20 mins bottom time, with 21/35 backgas and EAN50 deco gas.

With no failures, I will have a total runtime of 48 mins

With loss of EAN50, total runtime will increase to 68 mins.

Okay... that's a little more conservative than Vplanner on +2 (44/66), and a little more liberal on the lost-gas than Vplanner on +3 (45/72).

It's on +4 that Vplanner goes to 47/84.

Helium in the bottom mix seems to help, with air being:
+2 = 47/70
+3 = 51/76
+4 = 53/85

Still... the point was that even an extra 20 minute hang could pose a problem in open water. Of course, truly doing it right, you would have a team of safety divers and spare deco gas on the boat (or hanging on the upline)... always wise for an open water planned deco dive.