Dan - Human error in diving

[Ayisha]

PADI 2012 Instructor Manual
Confined Water Dive 1 Performance Requirements
9. Locate and read the submersible pressure gauge and signal whether the air supply is adequate or low based on the gauge’s caution zone.

Bill

Locating and reading a SPG and signalling adequate or low air supply is surely only a tiny part of gas management. "Based on the gauge's caution zone" completely disregards gas-integrated computers. Most analog gauges caution zones include only the last 500 psi, which is too little reserve to begin an ascent for many deeper dives or a turn-pressure for dives that require that you get back to the same point you started. The statement above is a start but is woefully inadequate in teaching any kind of gas management.

 

[Hawkwood]

Locating and reading a SPG and signalling adequate or low air supply is surely only a tiny part of gas management. "Based on the gauge's caution zone" completely disregards gas-integrated computers. Most analog gauges caution zones include only the last 500 psi, which is too little reserve to begin an ascent for many deeper dives or a turn-pressure for dives that require that you get back to the same point you started. The statement above is a start but is woefully inadequate in teaching any kind of gas management.

That is obvious, but that was not the objective of my post.

 

[DBailey]

I have read some great articles about gas planning, but a majority of those articles never mention anything about monitoring the gas underwater. I have had a couple students bring the gas planning articles to class. When I asked them, "Ok, you are now on your dive, how often do you check your air pressure?". I have received the response, "I don't need to check it. I did all the planning based on SAC rate, depth, and times, so I only need to follow my watch and depth gauge." In theory, it should be that easy. In reality, that student will end up as a statistic.

I submit that you can do ZERO gas planning (for a non-overhead, recreational dive), and as long as you monitor the gas properly and use common sense along with simple math, you should be able to survive the dive.

Personally, I think the root cause for the accidents is primarily the lack of common sense or people not using common sense. That applies to the instructor, LDS, dive operators, and the diver.

 

[TSandM]

DBailey, if your students are taking that message away from gas management articles, they have simply made an error. No amount of planning replaces vigilance in the water. What gas planning does is make the likelihood of a low on gas problem smaller -- if the diver has given the dive at least enough thought to compare his supply to the predicted demand, he'll either be more vigilant or take more gas (or make the dive shallower).

Edited to add: I just went and read Bob Bailey's gas management article again, as it is the one I most frequently reference when suggesting people learn about gas management. I found this at the end of the article:

During the dive …

• Monitor your own gas on a regular basis … every five minutes, at a minimum. It’s a good idea to monitor your gas more frequently as you go deeper, since you will be breathing it down faster at greater depths.
• If you are diving with an unfamiliar buddy, make sure to communicate your pressure to your buddy on a regular basis, and that they communicate theirs to you. This will give you an idea of their actual gas consumption compared to yours, and vice-versa. Familiar dive buddies have generally established this relationship already, through previous experience.
• Keep both your own and your dive buddy’s turn pressure and rock bottom pressure in mind. If you have difficulty remembering, write it on a slate or wet notes for reference during the dive.

I would say that, if anyone comes away from reading this article with the idea that they don't have to watch their gas while underwater, they either didn't understand or didn't finish the article.

 

[boulderjohn]

DBailey, if your students are taking that message away from gas management articles, they have simply made an error. No amount of planning replaces vigilance in the water. What gas planning does is make the likelihood of a low on gas problem smaller -- if the diver has given the dive at least enough thought to compare his supply to the predicted demand, he'll either be more vigilant or take more gas (or make the dive shallower).

Exactly.

For example, the TDI manuals that teach SAC and RMV tell you that when you look at your SPG, it should show you what you would expect it to at that point in the dive--but you should still look at that SPG to be sure.

 

[ScubaSteve1962]

I don't disagree, but I will provide a minor correction:

PADI 2012 Instructor Manual
Confined Water Dive 1 Performance Requirements
9. Locate and read the submersible pressure gauge and signal whether the air supply is adequate or low based on the gauge’s caution zone.

Bill

In my confined PADI dives our instructor stressed that when asked your pressure you should know it within 200 psi if above 1000, and 100 if below 1000 which meant constantly monitoring your guage or computer. And as far as the 88% percent rate on the first dive, could this be because the were vacation/trip divers and that's the only time they dive?

It's not too surprising, since the first dive is usually deeper and generally more demanding than the second.

Notwithstanding the "reverse profile" issue, if a two tank dive was a 40' reef followed by a wall, instead of the other way around, the DM would get a chance to determine if everybody is actually qualified for the wall dive.

The way things are done now, divers are dropped on the wall, then if they survive, the next dive is an easy reef.

flots.

Should the diver not pick such a demanding dive if they aren't prepared for it? Wouldn't this be part of your dive planning?

 

[flots am]

Should the diver not pick such a demanding dive if they aren't prepared for it? Wouldn't this be part of your dive planning?

Yes, that would be awesome. However new divers (and in fact, non-hardcore divers in general) are extremely unlikely to tell the DM that they don't like his choice of dive site, or even have a frame of reference for evaluating it.

I don't think I've ever heard anybody on a dive boat tell the DM to change the dive site, even though there have been many divers that were obviously completely unqualified and quite anxious, and had all sorts of problems underwater including panic, buddy separation and OOA.

flots.

 

[ScubaSteve1962]

Yes, that would be awesome. However new divers (and in fact, non-hardcore divers in general) are extremely unlikely to tell the DM that they don't like his choice of dive site, or even have a frame of reference for evaluating it.

I don't think I've ever heard anybody on a dive boat tell the DM to change the dive site, even though there have been many divers that were obviously completely unqualified and quite anxious, and had all sorts of problems underwater including panic, buddy separation and OOA.

flots.

So wouldn't any accidents that stem from this go under human error? The diver didn't research the OP, or the sites they visit. And didn't speak up, or over estimated their ability. Thus the 88% on the first dive?

 

[flots am]

So wouldn't any accidents that stem from this go under human error? The diver didn't research the OP, or the sites they visit. And didn't speak up, or over estimated their ability. Thus the 88% on the first dive?

It's certainly human error, however I'm not sure you can call it "diver error".

FWIW, I'm not sure that 88% is a useful number. It's like saying "My car keys are always in the last place I look"

flots.

 

[DBailey]

DBailey, if your students are taking that message away from gas management articles, they have simply made an error. No amount of planning replaces vigilance in the water. What gas planning does is make the likelihood of a low on gas problem smaller -- if the diver has given the dive at least enough thought to compare his supply to the predicted demand, he'll either be more vigilant or take more gas (or make the dive shallower).

Edited to add: I just went and read Bob Bailey's gas management article again, as it is the one I most frequently reference when suggesting people learn about gas management. I found this at the end of the article:

[/LIST]

I would say that, if anyone comes away from reading this article with the idea that they don't have to watch their gas while underwater, they either didn't understand or didn't finish the article.

Oh, I agree. They were set straight. To clarify, they brought this to class after their research online. We hadn't reached the gas planning/monitoring section of the class yet, so they jumped the gun. To the point of the article, every 5 minutes? Thinking back to my hoover days, that would have meant checking the gauges 6 times on the dive. Way too few for a new diver. Seeing how it takes three seconds to check it, you won't miss anything on the dive.

My parting commnet in class about gas monitoring is similar to what boulderjohn posted. The reading on your gauge should never surprise you.