Charlie99
Contributor
- Messages
- 7,966
- Reaction score
- 169
- # of dives
- 500 - 999
Thanks. Between your explanation and turning my brain back on, it now makes sense
Max. depth on Air
- Thread starter DIZZY
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Kaos
Contributor
My Nitrox fills cost me $14 compared for $5 air. That's a 180% increase. I can understand that the shops must stock up on oxygen and actually "do" the mixing, but it's still a sharp increase. But as much as I complain, I pay it, there is no price on safety.
Oddly enough, fills at Anthony's Key in Roatan were less severe than here, only $5 more per fill... throws away the "tourist gouging" theory
Oddly enough, fills at Anthony's Key in Roatan were less severe than here, only $5 more per fill... throws away the "tourist gouging" theory
captain
Contributor
Kaos, you say there is no price on safety but the question is if you dive the limits of the mix are you any more safe than diving the limits on air. I say no.
Mix gas was never developed as a safety issue. It was developed by the Navy and commercial diving industry to allow longer bottom times and deeper depths. In their business time is money. That is not the case in recreational diving except for the dive shops selling their mixed gas certification and fills.
Captain
Mix gas was never developed as a safety issue. It was developed by the Navy and commercial diving industry to allow longer bottom times and deeper depths. In their business time is money. That is not the case in recreational diving except for the dive shops selling their mixed gas certification and fills.
Captain
In '65 when Tom Mount did his study on narcosis, the question was not so much whether people could function at 200' on air, as that was done routinely and NOAA approved the use of air to 200' for research dives. Instead the issue was how much impact did the type of information and training provided to a diver have on their susceptibility to nitrogen narcosis. The big surprise was how badly divers who were given the expectation that narcosis was dibilitaing at shallow depths were in fact debilitated at shallow depths.
I find it ironic that the dive industry has done such an effective job lately of turning out divers who for the most part would fit into Group 1 of that study and have an almost irrational fear of narcosis and who hold a consensus that there is an elevated risk of being incapacitated by narcosis below 100' and that the risk is extreme below 130 ft. This overly conservative approach makes sense if you consider the need to certify a large number of divers (ie. consumers) with a lower overall level of training and at the same time ensure a low accident rate to ensure people keep entering the sport to enable continued growth in the industry. However what is good for the growth of the dive industry overall, may not always be what's best for an individual diver.
Similarly, the tech community has pushed the use of trimix (with very good reason at depths below 150 to 180 ft) to the point that some divers seem to also consider it safer at shallower depths in the 100-120 ft range despite the potential need for additional decompression on some profiles and the additional complexities presented by the mixing process. Consequently a lot of divers are paying additional cost in terms of both deco time and cash for what amounts to little benefit on dives that could be done safely on air by an experienced diver.
As for the bottom line and it's impact on what is considerd ok by the diving industry, Nitrox is a good example. Both the scientific community and the dive industry put forth fierce opposition to Nitrox until they discovered the financial benefits involved. The dive industry discovered that a small percentage of technically oriented divers were responsible for a disproportionately large percentage of equipment purchases and that nitrox would open up a whole new dimension of equipment sales and training. The scientific community discovered that a diver on Nitrox for about $100 a day could get the same bottom time at 80 ft as a diver living in a habitat for about $2000 per day. So virtually overnight everybody forgot their long held saftey concerns and Nitrox was suddenly ok and those using it were no longer risk taking cowboys because Nitrox was where the money was at.
I find it ironic that the dive industry has done such an effective job lately of turning out divers who for the most part would fit into Group 1 of that study and have an almost irrational fear of narcosis and who hold a consensus that there is an elevated risk of being incapacitated by narcosis below 100' and that the risk is extreme below 130 ft. This overly conservative approach makes sense if you consider the need to certify a large number of divers (ie. consumers) with a lower overall level of training and at the same time ensure a low accident rate to ensure people keep entering the sport to enable continued growth in the industry. However what is good for the growth of the dive industry overall, may not always be what's best for an individual diver.
Similarly, the tech community has pushed the use of trimix (with very good reason at depths below 150 to 180 ft) to the point that some divers seem to also consider it safer at shallower depths in the 100-120 ft range despite the potential need for additional decompression on some profiles and the additional complexities presented by the mixing process. Consequently a lot of divers are paying additional cost in terms of both deco time and cash for what amounts to little benefit on dives that could be done safely on air by an experienced diver.
As for the bottom line and it's impact on what is considerd ok by the diving industry, Nitrox is a good example. Both the scientific community and the dive industry put forth fierce opposition to Nitrox until they discovered the financial benefits involved. The dive industry discovered that a small percentage of technically oriented divers were responsible for a disproportionately large percentage of equipment purchases and that nitrox would open up a whole new dimension of equipment sales and training. The scientific community discovered that a diver on Nitrox for about $100 a day could get the same bottom time at 80 ft as a diver living in a habitat for about $2000 per day. So virtually overnight everybody forgot their long held saftey concerns and Nitrox was suddenly ok and those using it were no longer risk taking cowboys because Nitrox was where the money was at.
MMMerritt
Guest
205 FSW is my personal limit diving on air. A maximum depth of around 130 feet is generally the accepted limit for recreational scuba diving on air. A depth of about 230->240 feet is when the oxygen componet in air at this pressure is toxic to average humans, and many times result in convulsions, drowning and death. I have experienced effects of nitrogen narcosis as shallow as 65 fsw that changed my original dive plans while most other deeper dives down to a maximum of 205 FSW narcosis was not a problem.
Correct me if I'm wrong, but I believe that a PPO2 of 1.4 on air is reached at 177 feet. A dive past 200 feet on air would be a PPO2 of greater than 1.7.
That seems foolish to me....
Based on what I have been taught, 1.4 is the max "safe" PPO2, and 1.6 is considered safe for "rest" vs. "work" conditions. A dive past 230 would put the PPO2 at nearly 2.0.
What's down there that people need to dive to these depths on air anyway?
If something is that worthwhile, wouldn't it be wiser to take advantage of other gasses?
That seems foolish to me....
Based on what I have been taught, 1.4 is the max "safe" PPO2, and 1.6 is considered safe for "rest" vs. "work" conditions. A dive past 230 would put the PPO2 at nearly 2.0.
What's down there that people need to dive to these depths on air anyway?
If something is that worthwhile, wouldn't it be wiser to take advantage of other gasses?
Kaos
Contributor
When I say that Nitrox is "safer", I mean in terms that you absorb less nitrogen: which means less (not to say none) chance of undeserved DCS, less chance of Nitrogen Narcosis, and less chance of feeling sudden pain on the plane ride home (compared to an air diver).
If I'm to take a diving trip where all dives are in the 0-100 foot range, I would feel safer diving Nitrox throughout the week than on air, as long as I follow every safety precaution (Non-deco limits and Maximum Operating Depth) for the mix I'm using.
I do agree though that the POP limits of Nitrox make it dangerous at Depths past the 120 foot range. Which is why I have yet to convert my tanks to Nitrox for my local dives, since they are less in numbers (avg of one per week) but deeper (70-145 foot range).
Similar threads
