• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

12 1/2 Minutes!!

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.


Dairyland diver
Apr 7, 2001
I just read the news release about Genluca's breath hold after breathing 02.
I thought that I read an article a few years ago about Umberto doing 19 1/2 minutes. Was that ever officated by anyone? Is this going to be a new catagory?

Most of us know about the dangers of 02 below 20'. Even so, 12 1/2 minutes is a heck of a long time.

I remember Eric Fattah talking to me last summer about the possibilites of doing 20 minute shallow reef dives after surface breathing 02. That would really freak out the bubble blowers.


I heard that Pelizzari (or someone) did 21 minutes on oxygen. The Guiness Book of World Records will not acknowledge Martin Stepanek's 8'06 record because they already have an ancient record of 13.X minutes done on pure O2 at the bottom of a pool. They don't differentiate between pure O2 and atmospheric air.

Eric Fattah
BC, Canada
I had read that Pellizarri did 20 minutes in a lab with a doctor....he said that he stopped, not because he needed to breath, but because he thought that it was just a little strange, and that possibly something had gone wrong.
Frankly, 12.5 on O2 doesn't really impress me that much, considering Martin's 8+ on air.
The US Navy also did experiments to 20 minutes on O2 with good apneists. I'm sorry I don't have links for this info: my computer crashed in January and I lost tons of "Favourites" :(
I am really interested in doing some experiments with shallower Nitrox mixtures, say 36%. I would love to do a 10 or 12 minute freedive.
Erik Y.
Nearly tried it

I was once diving on the G.B. Church in Victoria. Some of my scuba diver friends were there and they were using 40% nitrox. We were going to do an experiment where I would take a breath of the nitrox and then dive the wreck at 80 feet. Unfortunately by the end of the day we had forgotten about it, but it would be cool to try; it would be a bit dangerous and a trial on a line with better safety would be in order, because to make use of the extra O2 you would have to hyperventilate off all your CO2, else you could have a deep blackout from hypercapnia. Please don't try this without proper knowledge and safety!

Eric Fattah
BC, Canada
  • Like
Reactions: Longfins
Eric Fattah please correct my physics if I am wrong- like I need to ask.;)

If you hyperventilate on 40% your po2 of 02 in your blood can't be over 40% in your blood?

WOuld this also be the case if I was breathing 32%, meaning that as long as I hyperventilated 32% I could never get above a 32% po2 in my blood?

Just wondering about a future of planning out my freedives like I do my nitrox dives.

Don't worry Cliff, I won't go out and try this tommorrow.:duh


I might wait a week or two first.;)
Jon, if I were to do this, I would do my breath-up on air, then take the final breath off the nitrox...this is what the navy and Umberto did. Any links to the Gianluca article?
Erik Y.
My opinion

Hyperventilating on pure O2 doesn't increase your O2 levels, it just drops your CO2. Even breathing atmospheric air, the hemoglobin in your blood is around 97-98% saturated. On pure O2, it goes up to about 100%, but the increase in oxygen stored in the hemoglobin is not much. But, you start with far more oxygen in your lungs, and possibly in your tissues (see below).

You must drop your CO2 to near-hypocapnia-blackout levels if you want to avoid a CO2 blackout. You will start the pure O2 breath-hold with a huge amount of O2; but each O2 molecule consumed produces 0.7 to 1.0 CO2 molecules (depending on RQ), so where will all that CO2 go? Your blood will get more and more acidic, until finally you go into CO2 narcosis and 'fall asleep' from CO2 'narcolepsy', despite huge O2 levels still in your blood. So, the main limit will be how low can you get your CO2 level before the breath-hold. I heard that residual volume is also a problem; with your entire lungs filled with oxygen, every molecule in your lungs can be 'consumed' and converted into CO2; the body has a large non-lung CO2 store, so the lung volume decreases almost without limit.

There are some other factors. At 100% O2, a significant amount of oxygen actually dissolves directly into the blood plasma; from there, the oxygen diffuses directly into the wet tissues, resulting in a whole-body non-blood oxygen store which is suddenly significant. If you take just your last breath on 100% O2, there will not be enough time for the whole-body O2 absorption. I heard that 10-30min of regular breathing on pure O2 are needed for the whole-body absorption. Then, hyperventilating for several minutes would be needed to blow off as much CO2 as possible without blacking out.

Again, be careful and don't do anything you crazy...

Eric Fattah
BC, Canada
Re: My opinion

Originally posted by efattah
Again, be careful and don't do anything you crazy...

Eric Fattah
BC, Canada

....says the guy who has dived to 89 metres! ;)
Erik Y.
>.If you take just your last breath on 100% O2, there will not be enough time for the whole-body O2 absorption. I heard that 10-30min of regular breathing on pure O2 are needed for the whole-body absorption. <<

Hi all,

First time poster here as I begin to explore this fascinating sport and what I'm interested in doing in it. I look forward to learning a lot from you all.

I don't want to sound like the Nervous Nellie here and I certainly respect Eric's incredible expertise; but having read lots of obits of divers suffering immediate O2 hits after gas switching, I felt compelled to repeat a note of caution.

We sometimes assume that 'everybody' probably knows the risks of pure O2 below 20' but I believe the extended audience (newbies like me) needs to understand that all elevated O2 partial pressures in gas (even Nitrox 40, etc) carry a risk of O2 toxicity.

Ventilating on pure O2 and then freediving to depth carries a significant risk of the more serious Central Nervous System (CNS) O2 hit as the O2 retained in lung tissues move more directly into the bloodstream. A 'sudden spike' CNS hit is possible if one takes a breath of an elevated mixture (ie. 'last breath on O2' or a breath off of Nitrox 40) while at or moving to a deeper depth.

'Whole body saturation' isn't necessary for an O2 hit on the CNS. There's theory that immersion triggering the 'Diver's Reflex' in itself makes one more susceptible as the body centralizes blood flow to key organs (including the CNS).

The complications of a CNS hit underwater are convulsions similar to a grand mal epileptic seizure leading to aspiration of water and drowning. It is sudden and dramatic. It remains a far too common cause of death for divers in the "extended range"; and is obviously more dangerous to those divers without full-face masks or any breathing aparatus at all.

Particularly to those divers who might feeled compelled to try diving to/from mixes of elevated O2; I implore to to learn the risks by reading the significant research available online.

Thoughts? Comments?

- Keith
I don't think that anyone on here was going to try this without proper support.
You bring up some of the issues with in water 02 use, but there are others.
It is possible to convulse at shallower depths if the water is cold, like in the Great lakes or Canada, and if you have a high exertion rate.
Another problem can occur becasue 02 is metabolized at a different rate than air. This can actually cause inner ear decompression sickness. The reason for this is becasue the 02 that was used to clear the ears is actually being metabolized by the body at the same time.
For anyone interested if further complications with using 02 in water there are numerous technical classes available through a wide vartiety of certification agencies. There are also many books on the subject. On e of the better ones that i have read is called OXYGEN AND THE DIVER. It goes through the history of of 02 and nitrox diving experiments that were done by the UK navy around world war II. To some up the book in one sentence would be this:
"You never know when your going to get hit because it often happens without any warning at all".
That being said, I have a bottle of 50% and another bottle of pure 02 in my basement that are calling me. I am waiting to see what happens to Eric first and then I'll get some friends to watch me. ;)

Hi Jon,

Nice to meet you.
I'll have to look up "Oxygen and the diver", sounds like an interesting one. In my years of scuba instruction I've honestly never heard of Inner Ear DCS...I wonder what the statistics are on that.

My mini-soapbox aside, I understand the attraction of higher PP O2 mixes more frequently available than ever. I also know there's a reading public out there that might consider O2 ventilations and/or diving too/from a buddy at depth a "short cut" to proper training and conditioning.

As for watching...I guess I'm at the point where I'm interested in watching people doing freediving "the old fashioned way" for the time being.

Anyone in the CA Bay Area? :)

- Keith
Dr. Goldman who runs the St. Lukes hyperbaric chamber was the one who infromed me about inner ear dcs about 10-15 years ago.
We were using an 02 hooka system to deco off of on our deeper dives. He was concerened at the time about in water 02 deco at depths deeper than 10' because of the number of seals that had toxed on rebreathers at 20' in cold water. I am not sure what studies he was refering to, just what he related to me.
I had originally gone in to find out about the huge swelling that I had in my neck after a series of deep deco dives. I called up DAN and wondered if I had Subcutaneous emphysema. After I was seen by about 10 doctors and one hyperbaric doctor, he came in and diagnosed me with the mumps! Then things really got interesting because they hadn't had an adult with the mumps at that hospital in over 5 years. Every intern in the place came in to check me out. One of the hazards of working with kids who weren't immunized I guess.
The following deco conversations I found to be pretty interesting.
In the following years I think that we have proven that tech divers can pull of 02 deco, at 20', in freezing water without a ton of seizures.
Don't worry about the soap box here. Most everyone on the list is very concerned about safety.
Oxygen breath-hold diving was studied at Duke University Medical Center for the Special Operations Command. The technique extends breath-hold time and eliminates the hazard of ascent hypoxia ("shallow water blackout") but increases the risk of altered consciousness due to hypercapnia -- particularly during exercise. The full project report is available on the web site of the Center for Hyperbaric Medicine and Environmental Physiology


Dick Vann
Oxygen Toxicity as per Navy Divers Manual

I may be spitting in the wind here, but here is what the Navy Divers Handbook says in reference to CNS O2 Toxicity:

CNS oxygen toxicity can occur when divers are exposed to more than 1.3 atmospheres of oxygen for a period of minutes to hours. Susceptibility to CNS O2 Toxicity varies from person to person. Individual susceptibility will vayt from time to time and for this reason divers may experience CNS O2 Toxicity at exposure times and pressures previously tolerated. Because it is the partial pressure of o2 itself that causes toxicity, the problem can occur when mixtures of oxygen with nitrogen or helium are breathed at depth. O2 toxicity is infulenced by the density of the breathing gas and the characteristics of the diving system used. Thus, allowable limits for oxygen partial pressures differ to some degree when specific diving systems are discussed in later chapters. In general, oxygen partial pressures at or below 1.3ATA are unlikely to produce CNS toxicity. Closed system O2 rebreathing systems require the lowest partial pressure limits, whereas surface-supplied helium-oxygen systems permit slightly higher limits.
Three major external factors contributing to the development of O2 Toxicity are the presence of a high level of Carbon Dioxide in the breathing mixture resultimg from CO2 absorbent failure, CO2 in the helmet supply gas, or inadequate ventilation during heavy exertion.
They go on to say more....but I have to get back to work...
The worst thing I can remember about being a commercial diver is the O2 tolerance test. Yearly, they blow you down to 60fsw in the chamber and make you breathe pure O2. You have to sit on your hands. Any little fidgeting movements and you would fail. It was a stupid test anyway, any one, any time, you could fail the test. I mean, if you started doing a dance(convulsions) they would bring you back to the surface and then test you again 3 days later.
I think that now they only test you in dive school.


DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing


ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.