did anyone see that ridiculous on the edge show that was on last night?

[nolatom]

im a new diver
i also seen the show last night
when i heard 250 foot dive on reg air i thought wow there luck all 3 didnt die
i was taught that the max deepth for air was 140 ft
im new so if im wrong /im wrong
im going to re read my manule tonite

If you look at your manual, you'll probably find the conservative maximum depth for compressed air is 1.4 atmospheres of oxygen. With 21% oxygen in air, that works out to 6.6 atmospheres (1.4 divided by .21 equals 6.66). At 10 meters salt water per atmosphere, that's 66 meters, or 218 feet. Below that depth (i.e. above 1.4 ata) the risk of oxygen toxicity rises to where trimix is a much better choice.

Most divers don't make a practice of going that deep on air anyway, as nitrogen narcosis makes such dives more difficult compared to trimix. So wherever you got the idea that 140 is plenty of depth for air, it's probably a good idea just from a narcosis standpoint.

I'm a rec diver so don't make a practice of going that deep anyway, I'm repeating what I've read and heard. You'll study these calculations when and if you take a basic nitrox course, since increased oxygen in the nitrox mix means oxygen toxicity occurs at shallower depths than with regular air, and you have to guard against it.

 

[BadLatitude]

they only did one that deep and only 2 of the 6 divers did it and with2 tanks each. only once ......... yes they could have brought 4 tanks and dove the rest of their previous dives on air. Did you even watch the show ? to say they would have needed tanks flown in daily is a weird comment if you did. especially since they only went down the main vertical shaft once and spent the rest of the dives mapping smaller un charted shafts off of the horizontal shaft.

 

[Santa]

the show is called Adventures on the Edge i dont remember what channel it was

It ran very recently on a Danish channel as part of a whole-night special on caves (like that would help anyone). Looked like your average national geographic/discovery-type stuff to me.

I'd go easy on those fella's on account of the tragedy involved, but I'm still dumbfounded that anyone associated with technical stuff like cave diving would go below 58-60 metres on air.

Maybe I'm being naive.

 

[gcbryan]

If you look at your manual, you'll probably find the conservative maximum depth for compressed air is 1.4 atmospheres of oxygen. With 21% oxygen in air, that works out to 6.6 atmospheres (1.4 divided by .21 equals 6.66). At 10 meters salt water per atmosphere, that's 66 meters, or 218 feet. Below that depth (i.e. above 1.4 ata) the risk of oxygen toxicity rises to where trimix is a much better choice.

Most divers don't make a practice of going that deep on air anyway, as nitrogen narcosis makes such dives more difficult compared to trimix. So wherever you got the idea that 140 is plenty of depth for air, it's probably a good idea just from a narcosis standpoint.

I'm a rec diver so don't make a practice of going that deep anyway, I'm repeating what I've read and heard. You'll study these calculations when and if you take a basic nitrox course, since increased oxygen in the nitrox mix means oxygen toxicity occurs at shallower depths than with regular air, and you have to guard against it.

Just for the record you calculations are incorrect 1.6 ata equates to 218 not 1.4 ata. Since we're dealing with absolute atmospheres you need to add one for the surface atmosphere which changes your 6.66 to 7.66.

 

[Mark Vlahos]

They made their choice. (realize this was in 1995 not 2005)

I think this is the key point in this entire discussion, the dive was several years ago. The diving community has learned a lot in the last ten years. Many of those lessons have been learned at great cost. Many divers have been severely injured or killed, from those experiences we learn. I dare say that ten years from now we may look back on 2005 and say how were we not all killed.

For me diving deep an equivalent nitrogen depth of 140 feet is about all I want. I am not yet trained in TriMix so if I can't make a dive work on NITROX with that 140 foot nitrogen depth I won't make the dive. The divers on the trip that the TV show is about made choices based on the experiences of the time, I dare say that this team would probably make different choices in 2005.

Caisson workers building the Brooklyn Bridge did not know about the hazards they faced, now modern construction sites are much safer.

We live, we learn.

Mark Vlahos

 

[Azza]

Helium in this country costs around $1200 for a g cylinder. You would get 2 fills out of a cylinder, 3 if you had a haskel.
I used to frequently dive deep air because of this reason. I no longer do as I feel I was pushing my luck back then. To fill a set of 12l doubles with 18/45 costs me $370. Thats blending it myself so you better include the initial set up costs to blend from your garage.
When I see people with bleeding hearts crying about paying $600 for a regulator in the Internet vs LDS threads I just laugh. What else can you do when the cheapest regulator in this country sells for around $800. And thats a crap reg. My Apeks cost me $1450 each. Hearing divers saying they never dive deeper than 30 metres on mix used to make me think that only rich people dived outside of NZ, that was until I found out you could get an 18/45 mix for about $40 in Florida.

Back in 1995, New Zealand had hardly heard of Technical Diving and He was even more expensive than it is today. Even now we still only have around 6 Technical Instructors in this country, maybe more now but not many.
10 years ago Technical Diving in this country was at about the same level as in the early 80's in the USA. Even the almighty Legend of cave diving, Sheck Exley, used to dive to over 400 feet on air on a regular occasion i the 80's.
Dont judge until you know the full story. Yes it was stupid but it wasnt uncommon for those times.

 

[nolatom]

Just for the record you calculations are incorrect 1.6 ata equates to 218 not 1.4 ata. Since we're dealing with absolute atmospheres you need to add one for the surface atmosphere which changes your 6.66 to 7.66.

Oops--you're quite right. Got to scrape the rust from my brain.

 

[Jasonmh]

Well, there are alot of good points in here about the gas issue (air vs. trimix) but there were also several other things in the show that were very concerning. It was months ago that I saw the show, but I am pretty sure my memory is correct in saying:
1- They talked about how remote the location was and that it was hard to get supplies there. How in the heck can you plan such an extensive operation and not have backup pieces of equipment? The safety diver got a hole in his drysuit and could not go down to drop off the deco bottles. There was no equipment for making repairs and no backup suits. Not very smart.
2- One of the ladies on the "team" said that she had no experience in cave diving and was counting on the other people there to "save her" if something went wrong. The group was experienced and should have realized that they would need every member of the team to be at a certain level to perform the dives.
3- They new the guy was sick and pushed it anyway. They said they knew the guy hadn't made as many "acclimation" dives as they thought he should but proceded anyway.
4- They acknowledged that they knew it would be much safer to use Trimix, but went ahead with the air anyway.

Alot of these things violate basic principles of diving, esp. in terms of not being prepared and diving beyond your limits.
I feel bad for the family of the deceased, and it is very true that they were experienced and made the call, and paid the price. But when I was watching it, it was like watching a train-wreck in slow motion. I just wanted to reach in to the TV and grabs the guys, and say "What in the hell are you thinking?"

 

[*Floater*]

Here is a little more reading for anyone interested in learning how reckless Dave was http://nzcaver.org/htg/articles/pearse.htm

Good read. Just one newb question, what kind of a dive is Pete Hobson referring to here: "We wanted to do a anal dive in the Midas Chambers and pull the lines out of there as well but the compressor finally gave out so we only had the air left in our partly used tanks to do what we could."

For those who didn't read the article, those guys were basically broke. They took what they were given by the sponsors and did the dives with it because that was their dream. They knew the risks.

 

[Azza]

For those who didn't read the article, those guys were basically broke. They took what they were given by the sponsors and did the dives with it because that was their dream. They knew the risks.

Thats pretty much about it.