Error 130 dives on Fake Nitrox

[Dan G]

There was some computer that would reset to a fictive 50% O₂ / 79% N₂ mix, thus giving the nitrogen loading of air with the MOD of the hottest nitrox mix. I guess it makes some sort of sense as a worst-case default to protect against a forgotten gas setting.

Oceanics do this, unless the user goes to the settings menu and turns this setting off. Reminds me a bit of how there are gas hot water heaters that when the gas supply to the HWH was shut off, it caused a specific part that regulated gas flow to break and require replacement. This made re-lighting the HWH impossible unless you knew to replace the part and knew how to replace the part. Fortunately the part only cost a few dollars, but the "forced safety" element seems the same as the Oceanic FO2 setting. In both cases, as simple reading of the directions explained all of this.

 

[dmaziuk]

It's called "fail safe": make the system impossible to use in order to prevent worse damage. The alternative is "graceful degradation" where the system continues to operate in a "reduced" capacity.

The textbook SCUBA example is computers that lock you out after violating mandatory deco vs. the ones that don't.

 

[OctopusLover]

If a diver uses a dive computer, he and only he is responsible to understand how it works for the type of dive he is doing. He and only he will suffer the consequences of possibly making a mistake.

This is frankly not good enough. If I changed your computer to altitude mode without telling you, would you really notice before your next dive? How many dives might it take for you to figure out your NDLs are suspiciously low and there's that little triangle on your screen you're not sure was there before?

Having gotten to know this diver through the week the liveaboard lasted, they were certainly not stupid nor irresponsible. Once they took the Nitrox course, they understood everything quickly. Your answer implies that every diver is responsible for fully reading (and regularly refreshing) the manual for their dive computer and I assure you literally nobody does this. Anyone looking to place blame on this diver for the situation just isn't living in reality.

The solution in my opinion is two-fold:

• In your AOW course, explain that NDL is different if you use Nitrox, it's a setting on your computer, if you are not Nitrox certified just know where the setting is and check it's off.
• If you're an instructor/divemaster, regularly ask people for their NDL just like you ask for their air. If someone's NDL doesn't match what would be reasonable given the dive and mix they're on, pull them aside and check their computer

Neither is complicated or hard to implement.

Yeas ago I bought a second hand Zeagle N2ition which allowed for three nitrox mixes only to discover that it reset itself to air after every dive. At the time I thought "effing lawyers," this is an annoying/imbecilic "safety" feature produced by dive nannies who must think divers are idiots-no one could be stupid enough to dive air on a 32% setting.

Guess not.

There was some computer that would reset to a fictive 50% O₂ / 79% N₂ mix, thus giving the nitrogen loading of air with the MOD of the hottest nitrox mix. I guess it makes some sort of sense as a worst-case default to protect against a forgotten gas setting.

Oceanic computers to this. My partner Veo 2.0 is an example. The choice is between

• Leaving the last setting (dangerous)
• Resetting to air (dangerous if you're on Nitrox and fail to get an MOD alarm)
• Resetting to a Nitrox setting so high that it will be impossible to ignore while keeping you safe. That's where the 50% default comes from. You can't go deep enough to ever get bent nor get oxygen toxicity because the MOD alarm will fire at 18 meters, which happens to coincide with the noob-depth-limit.

I set hers to the 50% default and after the first few times being annoyed, she's never forgotten to set her computer before a dive again

 

[stretchthepenn]

My first dive computer - an Aeris Atmos 2 - defaults ( I think - but it’s definitely an option) to resetting to a 50% mix after each Nitrox dive. I still haven’t decided if that’s a good idea or not.

I had that computer. Ugh.

It was relatively new to me, I was a relatively new nitrox diver, and I was diving the Oriskany. So for dive #2, I forgot to reset the percentage, and as soon as I hit the crow's nest, the computer started shrieking at me, claiming I was about to die horribly.

Realistically, I couldn't do a thing at that point -- I didn't know how to reset the F02 underwater (or even if resetting it mid-dive was possible) -- and surfacing, resetting, and re-descending would've meant aborting the entire dive. So I stopped and just floated for 20 minutes until everyone else ascended. Bah.

Sold the damn thing ASAP.

 

[boulderjohn]

our answer implies that every diver is responsible for fully reading (and regularly refreshing) the manual for their dive computer and I assure you literally nobody does this.

My first computer, back in the last millennium, had a manual with the same problem as every other one I ever saw. It has absolutely everything there is to know in it. That gives them an out for any issue--hey! It's in the manual. The problem is that in information, theory, too much information is the same as too little information. What you need to know is a handful of drops lost in the flood of what you don't need to know.

Not only that, what you do need to know is not placed logically in a section titled Here's what you need to know. I am sure that is intentional, too for it prevents an attorney from claiming that doing so invited the reader to skip vital information. So as a new computer user, I had to ) figure out first what I needed to know, and 2) then I had to find that information scattered throughout the manual.

Years ago I bought an early Dive Right trimix computer online, and it did not have a manual with it. I got a PDF version online. Well, it turns out that the version I got was a PDF rough draft of the manual that was circulating with reviewer comments in the margins. Several comments expressed concerns about how the information might possibly open them up to liability.

 

[dmaziuk]

My first computer, back int he last millennium, had a manual with the same problem as every other one I ever saw. It has absolutely everything there is to know in it.

There is a reason for "when all else fails, read the f..(ine) manual".

We got over it a long time ago and invented COBOL so that the users can just Use The Source, Luke, and see for themselves how it works. "Even managers can read COBOL"

 

[boulderjohn]

I read an article on the topic of technical writing. It said that back in the earliest days of personal computing, the best one on the market was made by Coleco. It was called the Adam. The problem was that its manual was unreadable. The sales people could not figure out how it worked, so they didn't show it to customers. Coleco would have gone under as a company if they had not come up with Cabbage Patch Dolls, which apparently did not need a manual.

 

[dmaziuk]

It's called "intuitive interface": an interface that works exactly as user expects. That's relatively easy to achieve when your product is Cabbage Patch Doll. With a multi-functional multi-modal device: not so much.

 

[tmassey]

If you're an instructor/divemaster, regularly ask people for their NDL just like you ask for their air. If someone's NDL doesn't match what would be reasonable given the dive and mix they're on, pull them aside and check their computer

As a technical diver, this is absolutely one of the steps we do in GUE-style (cave-style?) head-to-toe equipment matching before we splash: “Computer, on and set to the right gas.” That check has absolutely caught both me and dive buddies on multiple occasions.

To me, that check is absolutely as important as that check of the pressure gauge you do right before you get off the bench and waddle your way to the water’s edge, and should be 100% linked together in each diver’s mind.

 

[Kendall Raine]

• Leaving the last setting (dangerous)

If what you mean is "being stupid is dangerous" then I agree.

Stupid, as in:

• Forgetting to analyze your gas
• Forgetting to turn on your gas
• Forgetting to check tank pressure
• Forgetting to hook up your LPI
• Forgetting to close your cam straps
• Forgetting to wear your fins
• Forgetting to close your dry suit
• Forgetting to breathe
• Forgetting how to use your computer
• Forgetting to check your computer settings

Come to think of it, diving is really pretty dangerous.