How to Know When To Start Heading Up

[Web Monkey]

How do you know when to start heading up on a dive? I understand people use up air at different rates and the deeper you are the faster you use up your air supply. I never know at what psi I should start heading up to end my dives. I am always with an instructor or my Dad and they seem to know when to head up to the surface. I guess i just haven't dove enough to estimate how much air I will need to reach the surface ending my dive with still around 500psi left in my tank. I have an uwatec aladin prime dive console that I love but can't understand how to know when to head up. Is there a general rule of thumb on when to head up?
Any help would be greatly appreciated.

That's a great question!

First, I'd like to say that just because someone you dove with ended the dive doesn't mean they picked the right time or pressure. I've watched instructors run divers right out of air. You need to know how much you need, and take personal responsibility for it. You'll be much safer.

You need to end the dive:

• Before you or your buddy runs out of no-deco time
• Before you or your buddy's tank pressure drops below the amount of air it takes to get both of you safely to the surface if one of you runs out of air.
• When you or your buddy gets cold, tired, anxious, scared, creeped out or otherwise unhappy.

Note that doing the second item requires knowing how fast you and your buddy consume air at your maximum depth, then calculating how long an ascent would take, including any safety stop, and figuring what volume of air is required to accomplish this.

It's a little work, but well worth it, since it will prevent an "Oh sh**!" moment when your buddy is OOA and you look at your SPG and find out that you don't have enough left to do a safe ascent with him.

Terry

 

[Web Monkey]

On a recent cruise we made port at Cozumel and Caymans. I arranged dives with Ops in both locations, both well known and highly respected, their names come up quite often on this board.

You can't trust anybody but yourself, and maybe your buddy. When I signaled to the DM that my buddy was LOA (the DM was supposed to shoot a bag to signal the boat about 500 PSI ago), and he just flipped back "OK" and continued the dive.

The next signal was "You're number one!" and we left him.

Terry

 

[fnfalman]

I'm surprised nobody advised the OP to get an air integrated computer.

Get an air integrated computer then program in what you want your tank pressure to be at the end of the dive (i.e. at the surface after safety stop). Then go and have fun. The computer will give you a countdown of how many minutes you have left underwater due to neither running into No Decompression Limit (NDL) or due to running low on air. When it hits 1-minute or 0-minute, start your ascension, do your safety stop, get to the surface. Voila!!! You should have around 500-psi in your tank.

 

[ianr33]

I'm surprised nobody advised the OP to get an air integrated computer.

Get an air integrated computer then program in what you want your tank pressure to be at the end of the dive (i.e. at the surface after safety stop). Then go and have fun. The computer will give you a countdown of how many minutes you have left underwater due to neither running into No Decompression Limit (NDL) or due to running low on air. When it hits 1-minute or 0-minute, start your ascension, do your safety stop, get to the surface. Voila!!! You should have around 500-psi in your tank.

Thats all well and good but does the computer consider your buddy? What happens when one of you has a burst hose just before turn? Can the computer cope with that or does someone die?

 

[ScubaInChicago]

Thats all well and good but does the computer consider your buddy? What happens when one of you has a burst hose just before turn? Can the computer cope with that or does someone die?

That's what the "Spare Air" is for

 

[BDSC]

Thats all well and good but does the computer consider your buddy? What happens when one of you has a burst hose just before turn? Can the computer cope with that or does someone die?

If you had a burst hose just before you turn the dive wouldn't you just surface at that point with your buddy? Now no one dies!

 

[fnfalman]

Thats all well and good but does the computer consider your buddy? What happens when one of you has a burst hose just before turn? Can the computer cope with that or does someone die?

That's where the "Dive Plan" comes in.

The AI computer is a tool that can be used to manage air. No more, no less. Just like we all learn how to do the tables but then go use dive computers anyway.

 

[fresh_fish]

My standard dive plan goes as follows... Depth independent. 1/3 rule for gas and time. If I'm off navigating somewhere, I begin finding my way back at 1/2 gas, that way, I have my 1/3 for ascent still.

 

[Web Monkey]

Let us all applaud ScubaInChicago for "going there" and threatening
DEATH to a fellow diver.

Good on you ScubaInChicago! You deserve the greatest recognition this board can offer.

Sarcasm and gas planning aside, new divers don't belong inside wrecks, "even a little".

All it takes is a misplaced fin kick (maybe not even the diver's), a bump or a knocked off mask to turn "minor penetration" into the diver's last dive.

Terry

 

[fnfalman]

Sarcasm and gas planning aside, new divers don't belong inside wrecks, "even a little".

All it takes is a misplaced fin kick (maybe not even the diver's), a bump or a knocked off mask to turn "minor penetration" into the diver's last dive.

Terry

Don't you know that every dive is suppose to be penetration/deco dives? Don't you know that everybody suppose to know their Trimix deco tables by heart? Don't you know that if you were to wear clear skirted mask that you'd go blind by the glare? Don't you know that if you don't use a pony bottle, you'd die? Don't you know that if you were to use computer; specifically air integrated computer, you'd die? Don't you know that if you're not diving a backplate with HOG harness, you'd die?

It always makes me laugh to see the high & mighty posting in newbie forums and expecting the newbies to know how to execute an exploration cave dive in the anarctic or something.