Info Deeply Safe Labs: A website for dive computer testing

[Deeply Safe Labs]

Greetings divers,

Over the past half year or so, we have been conducting tests on dive computers using a miniature hyperbaric chamber. Some of the results we have found, regarding repetitive diving, we believe could be of concern. This was identified with our first test protocol, two square dives of 30 minutes at 30 meters (100 ft), spaced by a 90 minutes surface interval. The results show that some dive computers, specifically these that implement ZH-L16 C, compute significantly lower decompression times than other computers for the second dive while being similar on the first dive, some leeway considered. This aroused suspiscions that these implementations did not account for repetitive dives in any other way that simple offgasing during the surface interval. We first confirmed this with theoretical calculations, and contacted relevent manufacturers to bring this to their attention. Some of them simply confirmed that absence of additionnal procedures, without bringing any argument to why they are not taking into account aggravating factors, like the right-left pulmonary shunt.

Following this discovery, we have continued on testing computers, and have decided to upload a website showcasing extended results as well as some additional computers models. More recently, we added another test protocol, designed by Professor A. A. Bühlmann in the 1994 UHMS workshop named "The Effectiveness of Dive Computers in Repetitive Diving", consisting of 6 dives for 16 minutes at 30 meters, spaced by 75 minutes of surface interval. We found the results to show even more cause for concern.

We have detailed why we find these results concerning on the website, under the sections "Forewords", "Test conditions" and "Guide to interpreting results". Therefore, I will not be detailing the reasons in this initial post, as it would be way too long, so we encourage you to read said sections instead.

The website is available at the following link: Deeply Safe Labs (works best on a computer screen).

Even though I am a former technical manager, computer specialized, from a long installed diving equipment manufacturer, I am no Professor, Doctor, or any kind of such experts. I have been doing this in collaboration just with experienced divers having a strong interest in decompression theory. We are eager to read what any of you may think about our analysis, and will gladly answer any question you may have on our work.

Best regards,
Eric,
Deeply Safe Labs.

 

[lowwall]

You are starting with an assumption that the ZH-L16 C is lacking when it comes to repetitive dives. What is the basis for this assumption?

Frankly, I would prefer that computers that profess to follow a given algorithm actually do so rather that adding undocumented modifications.

 

[Pearlman]

Sacrilege has been committed! Now waiting to witness the blowback (incl. but not limited to poking holes into the testing methodology, etc., etc.,).

Not an expert on algorithms - but the page “guide to interpreting results” has some interesting and agreeable viewpoints that meet my own personal confirmation bias - as I had watched all the video interviews of Dr. Bruce about the RGBM model before I got the Suunto and decided to risk the stupid lockout mode of their DCs.

 

[Deeply Safe Labs]

Hi @lowwall ,

Thank you for your input.

I believe care must be taken when referring to ZH-L16 C. ZH-L16 C is a set of parameters, which in itself does not constitute an algorithm, but simply limits to be used alongside an Haldane model. On that regard, I don't believe we have ever said that ZH-L16 C was lacking, regarding repetitive dives or any other subject for that matter.

What we are saying is that ZH-L16 C implementations that we have tested do not account for repetitive dives in any other way that simple offgasing during the surface interval. We first confirmed this with theoretical calculations, and contacted relevant manufacturers to bring this to their attention. Some of them simply confirmed that absence of additionnal procedures, without bringing any argument to why they are not taking into account aggravating factors, like the right-left pulmonary shunt.

I have no doubts on the ability of properly trained technical divers to adapt their conservatism to account for these factors. But here are two things to consider:
First, calling divers stupid for not understanding gradient factors or showing no interest in decompression theory sounds quite harsh and seems to be an emotional response,
Second, the Mares Puck 4 is the perfect example of a should be technical computer aimed at a recreational audience that most probably don't have the skills and knowledge that you technical divers have.

We haven't tested the Puck 4 but, on paper, it should be very similar to the Sirius, which we have.

Best regards,
Eric Frasquet,
Deeply Safe Labs.

 

[cerich]

Sacrilege has been committed! Now waiting to witness the blowback (incl. but not limited to poking holes into the testing methodology, etc., etc.,).

Not an expert on algorithms - but the page “guide to interpreting results” has some interesting and agreeable viewpoints that meet my own personal confirmation bias - as I had watched all the video interviews of Dr. Bruce about the RGBM model before I got the Suunto and decided to risk the stupid lockout mode of their DCs.

you don't mind the fake data?

 

[cerich]

Hi @lowwall ,


First, calling divers stupid for not understanding gradient factors or showing no interest in decompression theory sounds quite harsh and seems to be an emotional response,
Second, the Mares Puck 4 is the perfect example of a should be technical computer aimed at a recreational audience that most probably don't have the skills and knowledge that you technical divers have.


Best regards,
Eric Frasquet,
Deeply Safe Labs.

Can you explain your conclusion in the second paragraph of the above quoted versus the assertion in the first? Because seems to me the second is saying that recreational divers shouldn't be using a computer with adjustable GF's.

 

[cerich]

Hi @lowwall ,

Thank you for your input.

I believe care must be taken when referring to ZH-L16 C. ZH-L16 C is a set of parameters, which in itself does not constitute an algorithm, but simply limits to be used alongside an Haldane model. On that regard, I don't believe we have ever said that ZH-L16 C was lacking, regarding repetitive dives or any other subject for that matter.

What we are saying is that ZH-L16 C implementations that we have tested do not account for repetitive dives in any other way that simple offgasing during the surface interval. We first confirmed this with theoretical calculations, and contacted relevant manufacturers to bring this to their attention. Some of them simply confirmed that absence of additionnal procedures, without bringing any argument to why they are not taking into account aggravating factors, like the right-left pulmonary shunt.

I have no doubts on the ability of properly trained technical divers to adapt their conservatism to account for these factors. But here are two things to consider:
First, calling divers stupid for not understanding gradient factors or showing no interest in decompression theory sounds quite harsh and seems to be an emotional response,
Second, the Mares Puck 4 is the perfect example of a should be technical computer aimed at a recreational audience that most probably don't have the skills and knowledge that you technical divers have.

We haven't tested the Puck 4 but, on paper, it should be very similar to the Sirius, which we have.

Best regards,
Eric Frasquet,
Deeply Safe Labs.

Your new page makes a lot of assertions regarding scientific studies but doesn't have any references. In scientific study or academia that is called.. USELESS.

You are guilty of the very thing you are being dismissive about regards those who question your methods or conclusions.

 

[tursiops]

What we are saying is that ZH-L16 C implementations that we have tested do not account for repetitive dives in any other way that simple offgasing during the surface interval.

Why should they?

 

[Pearlman]

you don't mind the fake data?

I am now aware of any but if you have some pointers I would like to read about it.

 

[Duke Dive Medicine]

Your new page makes a lot of assertions regarding scientific studies but doesn't have any references. In scientific study or academia that is called.. USELESS.

You are guilty of the very thing you are being dismissive about regards those who question your methods or conclusions.

I think it it is reasonable to assume good intent on the part of the OP and make allowances for English likely being a second language. There are some fine scientific minds on SB, and with that comes the opportunity to share feedback in a constructive manner.

Best regards,
DDM