Don't breathe tanks to zero?

[Abdullah]

Someone can (and will no doubt) argue that you are getting the benefit of 36% on a 30' training dive but I would claim nonsense.

I'll take one for the team... The benefit on shallower dives isn't in extra bottom time, you'll probably run out of air before you hit a deco limit anyway. The benefit is in reduced nitrogen loading (which is always a good thing).

Some divers are focused on bottom time, while others are focused on why you get more bottom time. It's your money, and which ever strategy you decide to go with is your business. But saying it's nonsense to dive EANx on shallower dives is not an informed opinion, it's only your opinion.

 

[GrumpyOldGuy]

I purposely breath a tank to empty on occasion right before VIP. I want to know exactly how it feels to run out of air. Both from a technical view and from a mindset, it is a sobering experience. Of course I only do it in 15' with a a redundant air source handy and checked, in my local fresh water hole. I can tell you, ITS NOT THE SAME AS SIMULATION BY TURNING OFF THE VALVE! It is more subtle at first. Other than that they never see less than 300.

 

[chrpai]

I'll take one for the team... The benefit on shallower dives isn't in extra bottom time, you'll probably run out of air before you hit a deco limit anyway. The benefit is in reduced nitrogen loading (which is always a good thing).

I'm not going to disagree that reduced nitrogen loading occurs..... but I would argue that this isn't in itself a benefit. NDLs at 35' are what, 200+ minutes? That's over 3 hours. New O/W divers have SAC rates of 1+ SCFM and tend to get 30 minute dives in. They also tend to do 2 dives a day. This means you've only used 1/3 of your allowable NDL. There is already enough conservatism built into the "system" that you don't need to add more.

I'd argue that until you start doing 60 - 130 and have a decent SAC rate that there isn't any point of adding in the conservatism and/or extended run times.

It is good to see his EANx rentals cost $7 ( $15 here ) so it's not the worst thing in the world but I wouldn't go around thinking I'm all that safer or "feeling better" doing it.

 

[Abdullah]

I'm not going to disagree that reduced nitrogen loading occurs..... but I would argue that this isn't in itself a benefit. NDLs at 35' are what, 200+ minutes? That's over 3 hours. New O/W divers have SAC rates of 1+ SCFM and tend to get 30 minute dives in. They also tend to do 2 dives a day. This means you've only used 1/3 of your allowable NDL. There is already enough conservatism built into the "system" that you don't need to add more.

I'd argue that until you start doing 60 - 130 and have a decent SAC rate that there isn't any point of adding in the conservatism and/or extended run times.

It is good to see his EANx rentals cost $7 ( $15 here ) so it's not the worst thing in the world but I wouldn't go around thinking I'm all that safer or "feeling better" doing it.

In the long run, your body will be better off without the excess nitrogen. Most people feel better after a long dive on EANx as well (all else equal).

$15 seems high for a EANx fill. It costs about $7 for a one time fill or about $6 for a 12 tank fill card here. Oman was very similarly priced. What makes Texas so special?

 

[beanojones]

Not sure if this is what you have, but over balance (Apkes, Oceanic/Hollis) actually refers to IP increase with respect to depth, not tank pressure.

And in other regs, overbalancing refers to the fact that breathing gets easier when the tank is empty.

But regardless of why and what, there are plenty of regs that give no warning whatsoever until they stop delivering air. Since this thread is about breathing to zero, its worth noting what happens to breathing a tank completely dry. And until someone breathes their own regs down to zero (adn as noted it ain't the same as turning a valve off), they have no idea what their regs will do when they breathe them to zero.

---------- Post added July 6th, 2013 at 09:46 AM ----------

I purposely breath a tank to empty on occasion right before VIP. I want to know exactly how it feels to run out of air. Both from a technical view and from a mindset, it is a sobering experience. Of course I only do it in 15' with a a redundant air source handy and checked, in my local fresh water hole. I can tell you, ITS NOT THE SAME AS SIMULATION BY TURNING OFF THE VALVE! It is more subtle at first. Other than that they never see less than 300.

As the kids say, word.

Somewhat experienced divers should intentionally run out of air a few times so they actually know, rather then 'internet know' what they are talking about. Its inexcusable to be an instructor and talk about OOA (and CESAs etc) without having done enough of them to actually know what the fsck happens in real life.

And then they should open up their tanks to see if they actual get water in the tank. Rather than just guessing and calling it fact.

There has already been one person in the thread doubt that fast draining a tank can make for water inside the tank. Since it is easy enough to check, then check it.

 

[boulderjohn]

But regardless of why and what, there are plenty of regs that give no warning whatsoever until they stop delivering air. Since this thread is about breathing to zero, its worth noting what happens to breathing a tank completely dry. And until someone breathes their own regs down to zero (adn as noted it ain't the same as turning a valve off), they have no idea what their regs will do when they breathe them to zero.

To me, it depends upon depth. I don't think any regulator made today gives any warning whatsoever in a pool, which makes the air repletion exercise in confined water a waste of time. It is supposed to let the diver know what it feels like to start running out of air, but it doesn't. On the other hand, the high quality regulator I use for a stage bottle will give ample warning at, say, 150 feet. Since this thread is in Basic Scuba, I would say the average diver reading this should not be expecting a warning.

 

[GrumpyOldGuy]

In the long run, your body will be better off without the excess nitrogen. Most people feel better after a long dive on EANx as well (all else equal).

$15 seems high for a EANx fill. It costs about $7 for a one time fill or about $6 for a 12 tank fill card here. Oman was very similarly priced. What makes Texas so special?

The data is sketchy at best about people "feeling better". What is good for someone diving close to NDL does not extrapolate in a linear matter to those diving well below NDL. I do enjoy my 32%, my local dives are at altitude and are thus always NDL limited and I think I feel better. Not sure I could pass a double blind "taste test". It does however also cost me 2X ($7 vs $14 for 32%). The premium probably has to do with fill method, buying oxygen to mix and taking the time to bend is more expensive to process than banking off a membrane system. In a crowded market, an LDS might lower prices to bring in the customers. In a dive area say like West Palm Beach, the advantages of diving Nitrox are huge due to the nature of the dive sites and cheap Nitrox is a good marketing technique to differentiate your shop. In Texas, it's not crowed, the LDS can mostly choose what they want to charge.

 

[captain]

And in other regs, overbalancing refers to the fact that breathing gets easier when the tank is empty.

But regardless of why and what, there are plenty of regs that give no warning whatsoever until they stop delivering air. Since this thread is about breathing to zero, its worth noting what happens to breathing a tank completely dry. And until someone breathes their own regs down to zero (adn as noted it ain't the same as turning a valve off), they have no idea what their regs will do when they breathe them to zero.

---------- Post added July 6th, 2013 at 09:46 AM ----------



As the kids say, word.

Somewhat experienced divers should intentionally run out of air a few times so they actually know, rather then 'internet know' what they are talking about. Its inexcusable to be an instructor and talk about OOA (and CESAs etc) without having done enough of them to actually know what the fsck happens in real life.

And then they should open up their tanks to see if they actual get water in the tank. Rather than just guessing and calling it fact.

There has already been one person in the thread doubt that fast draining a tank can make for water inside the tank. Since it is easy enough to check, then check it.

Depending on the due point of the air in the tank and to what temperature the tank dropped to it is possible for liquid water droplets to form on the interior tank walls but most would likely evaporate once the tank came back to ambient temperature for a period of time.

 

[chrpai]

In the long run, your body will be better off without the excess nitrogen. Most people feel better after a long dive on EANx as well (all else equal).

$15 seems high for a EANx fill. It costs about $7 for a one time fill or about $6 for a 12 tank fill card here. Oman was very similarly priced. What makes Texas so special?

In the long run? You could say the same thing about not diving at all. The exposure is acceptable.

What is so special about (central) Texas? It's probably a number of factors that are all in a big feedback loop. I can't say where it "starts" but I know where it starts for me. No one banks the stuff here. So the first decision is to bother O2 cleaning your tanks. The shops want $50 per tank for that. Once you make this choice you can no longer get fills at Windy Point scuba park. I did 120 dives last year @ $4 per air fill that's $480. For nitrox ( in my tanks ) that would be 120 dives at $12 per fill + $50 for O2 cleaning or $1500. Tell me, are the nitrox benefits really worth $1000?

Most divers say no. So the shops don't sell much nitrox. Therefore they don't feel the need to invest in making their business model more efficient. They can claim they offer it even though they make just enough to feed their classes and the occasional diver that wants it.

 

[Slamfire]

In the long run, your body will be better off without the excess nitrogen. Most people feel better after a long dive on EANx as well

The human body does have a tolerance to certain levels of nitrogen loading with apparently no adverse effects. This is what dive tables and computers try to reflect when they tell you that your NDL is in the order of hundreds of minutes for certain shallow depths.

When you reduce N2 loading by replacing it with O2 loading you are not necessarily getting a freebie in the long run. O2 loading increases free radicals in your body and it is an oxidizing agent. Have you heard in the media of products that claim to be powerful antioxidants that help slow down aging? Well, O2 is the opposite. It is a powerful oxidant.