In an O2 fill desert

[Wibble]

Let’s say 45 minutes of 100% for deco at 20 and 10 foot stops. If you got onto 50% at 70feet you could get a lot of diving out of an al40 of O2 . What I’m wondering is how much O2 at 100% does an average diver need.

Need to take oxygen breaks too. Drives the CNS through the roof unless you move up to 5m/16ft to bring down the PPO2. That and the hassle of getting high pressure 100% makes other alternatives far more attractive.

 

[jlcnuke]

Let’s say 45 minutes of 100% for deco at 20 and 10 foot stops. If you got onto 50% at 70feet you could get a lot of diving out of an al40 of O2 . What I’m wondering is how much O2 at 100% does an average diver need.

As mentioned, none of this is for the "average" diver. Doing deco in caves, I've only used 100% O2. For diving like that, a 90+ minute runtime dive in many Florida caves can easily rack up ~20-25 minutes of 100% deco time at 20 ft (14-20 cu ft of O2 with .35-.6 cu ft consumption). If you want to do 2 dives per day and not swap deco cylinders, or plan to be able to share deco with your team if their gas is gone for some reason, then having at least double that would be a prudent plan imo. That means a full AL40 usually.

There's a reason so many divers that do this type of diving regularly have their own booster(s) or are diving where getting 100% O2 fills to full pressure in an AL40 is easy (i.e. US cave country in FL).

 

[tbone1004]

As mentioned, none of this is for the "average" diver. Doing deco in caves, I've only used 100% O2. For diving like that, a 90+ minute runtime dive in many Florida caves can easily rack up ~20-25 minutes of 100% deco time at 20 ft (14-20 cu ft of O2 with .35-6 cu ft consumption). If you want to do 2 dives per day and not swap deco cylinders, or plan to be able to share deco with your team if their gas is gone for some reason, then having at least double that would be a prudent plan imo. That means a full AL40 usually.

And full al40s are bricks so I usually prefer to go for 2200-2400 in al80s

 

[Celt]

As mentioned, none of this is for the "average" diver. Doing deco in caves, I've only used 100% O2. For diving like that, a 90+ minute runtime dive in many Florida caves can easily rack up ~20-25 minutes of 100% deco time at 20 ft (14-20 cu ft of O2 with .35-.6 cu ft consumption). If you want to do 2 dives per day and not swap deco cylinders, or plan to be able to share deco with your team if their gas is gone for some reason, then having at least double that would be a prudent plan imo. That means a full AL40 usually.

There's a reason so many divers that do this type of diving regularly have their own booster(s) or are diving where getting 100% O2 fills to full pressure in an AL40 is easy (i.e. US cave country in FL).

Getting over 20min deco on 100% at 20 feet with a run time of 90min would be a serious penalty on the second dive of the day. But yeah I’d need 700ltrs of O2 for 30 minutes at 65m if I had to do all my O2 deco at 20 feet not to mention the 30 minutes of air stops. It would be a terrible plan for me. Much better to get on to 50% at 70 feet.

 

[Manatee Diver]

@mac64 it is as @jlcnuke says, I meant as back gas. I don't need two sets, but having two sets eases logistical concerns, even with fairly easy access to the fills I want. If my deco bottle didn't last me 2-3 dives at a time, I would probably have two AL40s for oxygen too.

 

[Tracy]

And full al40s are bricks so I usually prefer to go for 2200-2400 in al80s

So I'm not the only one. My normal breather bailouts are an 80 of 18/45 and an 80 of 50/20 @ 2600.
I'm not using the 50/20 to combat HPNS, It just carries so much better coupled with a shorter fill.

 

[Celt]

Need to take oxygen breaks too. Drives the CNS through the roof unless you move up to 5m/16ft to bring down the PPO2. That and the hassle of getting high pressure 100% makes other alternatives far more attractive.

I really like 50% O2 for deco as I can get on it deep, it cuts the shallow stops and it’s great for decanting . The shallow stops can be a real pain in a heavy sea. You mentioned 80% must check that out and see how it looks.

 

[Wookie]

I really like 50% O2 for deco as I can get on it deep, it cuts the shallow stops and it’s great for decanting . The shallow stops can be a real pain in a heavy sea. You mentioned 80% must check that out and see how it looks.

I like 32% for the same reason.

 

[Wibble]

I really like 50% O2 for deco as I can get on it deep, it cuts the shallow stops and it’s great for decanting . The shallow stops can be a real pain in a heavy sea. You mentioned 80% must check that out and see how it looks.

I like 32% for the same reason.

What, you mean that one size doesn't fit all diving circumstances??

 

[Wookie]

What, you mean that one size doesn't fit all diving circumstances??

I KNOW, right?