Quite comfortable on air until ~165ish... then I start wishing I had a little He in the mix. Usually have a healthy supply of 10/50 around so I don't have to. Compromises I used to be willing to make on OC seem unnecessary with a rebreather.
Deep Air Poll. Well, Someone Has To Put Their Head Over The Parapet...
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oldschoolto
Contributor
Diving air to 150-170 on a wreak when I was really young.... And that was with penetration.... I don't go deep anymore.... Nothing to do there... 
Jim...
Jim...
True… and you also get to remember how cold you can get without your heart stopping!
There is a happy medium and the number varies significantly with the individual and near-term exposure. However, I believe a more practical recommended limit is closer to 50 M/165' than the 40 M/130' limit that dominates thinking in the North America.
True… and you also get to remember how cold you can get without your heart stopping!
There is a happy medium and the number varies significantly with the individual and near-term exposure. However, I believe a more practical recommended limit is closer to 50 M/165' than the 40 M/130' limit that dominates thinking in the North America.
What's this "cold" you speak of? I'm diving a rebreather in Florida. LOL, nothing cold about that.
Tell that to the diver in this video, he was on Christmas Island 5° above the equator.
For divers reading this who are unfamiliar with Helium, its thermal conductivity is much higher than Nitrogen. Also keep in mind that about 50% of our thermal loss is through reparation. Bottom line, shirt-sleeve comfortable in a saturation chamber at 850' is about 92° F. You literally go into uncontrolled shivering at 85° F. Of course the much lower percentage of Helium in Trimix above 100M/328' is much less taxing, but still very significant. Truth be told, we just like the sound of our voices on Helium.
Dr. Lecter
Contributor
There's a significant thermal retention effect with a CCR, though, yes?
Also keep in mind that about 50% of our thermal loss is through reparation.
Not on a rebreather. There's an exothermic reaction of the sorb removing CO2 which provides heat and I'm blowing 98.6F hot air into the rebreather with every breath. Granted, some of that is lost by the thermal conductivity of water against the breathing loop, but I'm still breathing warm, moist dry air.
FYI. I used to do 4 hour working dives in 30F. I did this every day for 6 months. Some of these dives were on HeliOx. There comes a point where you are just fuggin cold. I'm no fuggin colder on air than I am fuggin cold on Helium in 30F at 4 hours. I'm equally fuggin cold on both dives.
---------- Post added June 5th, 2013 at 09:29 PM ----------
Yes, on some dives, the air I'm breathing is actually too warm.
Somehow I doubt this fact is enough to convince those poor guys in the video.
FYI for divers who arent up on breathers: There is an exothermic chemical reaction between the CO2 and the absorbent that does increase the thermal energy in the breathing loop. As Superlyte27 discussed, it can be significant when the water temperatures are high and the helium content is relatively low even though heat generation is just in the calories/minute range. Unfortunately the net heat loss through respiration rate can turn negative very fast with a lot more downside potential than up.
The guys in the video were cold because they were in cold water at 300+ feet deep in wetsuits. What's the thermal protection of a wetsuit that has been crushed by 10+ atmospheres of pressure? Easy: None.
It has very little/nothing to do with the fact that they were on Helium.
I've spent hundreds of hours on Heliox in cold water. I've spent hundreds of hours on Air in cold water. The difference on OC is very slight. The difference on CCR is close to non-existant.
It has very little/nothing to do with the fact that they were on Helium.
I've spent hundreds of hours on Heliox in cold water. I've spent hundreds of hours on Air in cold water. The difference on OC is very slight. The difference on CCR is close to non-existant.
The diver in the video was probably not even wearing a wet suit.
Richard Pyle?
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