How is scrubber exhaustion measured?

[MadUKDiver]

@super scrubber check out this article - Rebreathers and CO2 – Fact, Fiction and Voodoo, it will help you understand more about CO2 and how the end point of a scrubber is measured. The CE test standard for rebreathers is EN14143.

 

[super scrubber]

This is really dangerous, and you would be a fool to try it. I'd strongly recommend picking a different project, or to at the very least modify this project such that nobody needs to actually dive the rebreather. F*** around here and there's a good chance you will find out.

[edit to add: on re-reading this thread, this guy has got to be a troll. If you are a troll, congratulations, ha ha, you got me. If you are not a troll, take the advice in this thread and abandon this idea]

I wish I was a troll but no it's a project I got assigned to as a senior engineering student. It shouldn't be the hardest thing to make since they used them in WW2 but yeah it has to be made and tested for the project so I'm kinda SOL if I don't make it. Getting as much info as I can on rebreathers is key right now for me.

 

[grantctobin]

I wish I was a troll but no it's a project I got assigned to as a senior engineering student. It shouldn't be the hardest thing to make since they used them in WW2 but yeah it has to be made and tested for the project so I'm kinda SOL if I don't make it. Getting as much info as I can on rebreathers is key right now for me.

I would adore knowing the university behind this

 

[super scrubber]

Please rethink your goal. On the advice of many of your advisors (us), you've come to the conclusion that you should do a simulated dive instead. Use an ESP 32 set up to measure O₂ and CO₂ before and after the scrubber. Create a breathing mechanism and add CO₂ to the mix while bleeding some off.

This project is not worth your life. I know at least a dozen people that have died on tested rebreathers. No, not "know of", but I considered them actual friends and dove with at least half of them. One was set to teach me about rebreathers and died on his a few days before the class. Some OW divers refer to them as "little boxes of death". Death on a rebreather is completely painless with absolutely no advance warning you're going to die. It's my opinion that one of those deaths was a suicide because of this. He had advanced cancer and was in constant pain.

I appreciate the advice and will definetly use the ESP 32 to set up the scrubber material, thank you for that! Also I'm working in a team so it's a bit better but if I don't make the rebreather I fail the class. I have a few months to make it so I'm just trying to get as much research now as I can and make it as safe as possible. I'm sorry about your friends too though. I know they are risky with the chance of oxygen toxicity so I'm trying to make mine as ventilated as possible. Thank you for all the information too, I'll keep this all in mind.

 

[The Chairman]

with the chance of oxygen toxicity

There's hypoxia, caustic cocktails, over-breathing, and many, many more issues encountered in the creation of a rebreather. Oxygen toxicity is two-fold and "venting" is not a valid solution.

When I was young, I thought all those old fogies were way to conservative. After all, I had this indomitable spirit and would live forever. Sigh. As you age you find that all those needless risks only thinned out the gene pool. No need to vie for the Darwin award. Make the rebreather... but do a dry dive on it. Get certified on a certified rebreather FIRST, so you'll know all the ways it's trying to kill you. There are old divers. There are bold divers. There are no old bold divers.

 

[Dsix36]

First of all - Any school that would knowingly force a student to test an experimentally made project rebreather is the same thing as asking you to swim in alligator infested waters. Only difference is that you have higher probability of surviving the alligators. I find it difficult to fathom this from any educational institution.
I am one of the "special" people that have made, tested, and dived with a rebreather that I made. I have years of open water experience, years of mechanical experience, and years of rebreather experience BUT - This was no easy task and the testing prior to use was in the range of 100 hours underwater with it in various scenarios. I spent over 2 years researching and talking to many dive buddies and "old timers" to learn as much from others with even more experience than myself before I ever even began to think about designing it. I do trust my life to it now and still use it frequently.
Most people that have the knowledge that you seek will not be very forthcoming due to your lack of experience. Please ask your teachers for another option or find a school that does not force you into potentially fatal activities.

 

[Duke Dive Medicine]

My final is diving in a homemade one for 1 hour in my DIY one so I'm SOL if I don't dive in it. I'm trying to get as much info as I can so I can build in a mega factor of safety.

I'll add my comments to the growing list. If you do this without any diving experience and training in a CCR, much less the highly specialized education and experience necessary to build a safe, fuctioning one, the likelihood is high that you'll meet someone like me professionally. Please reconsider your project and perhaps, as other posters have suggested, your choice of educational institution. If you aren't trolling and you truly were assigned this project by an educator at an accredited (presumably) university, that educator is placing you in an unacceptably dangerous position and is incurring considerable liability for both himself/herself and the institution. If you need an out, PM me and I'm happy to contact him/her personally.

Best regards,
DDM

 

[broncobowsher]

I wonder if the professor even understands the risks of the assignment they requested? I'm guessing not.

I could just see the headlines. Student dies due to Professors assignment.

 

[Akimbo]

It is not unreasonable to build a tabletop rebreather as a demo . It is another thing entirely to require diving it, or any other device, without any proper training.

The first time I saw someone black out in the water was testing a home-brew O2 rebreather in a swimming pool. The man was a very experienced diver and had a PhD in chemistry. He knew better but forgot to purge the loop.

 

[Wibble]

One of the things that amazes me about rebreather design is how subtle many of the features are implemented.

From first principles, a rebreather is a very simple piece of kit. However, there's so many tiny things that are built into the final design which makes it safe to use. For example where the oxygen is injected: inhale or exhale side; where in the design are the cells, before or after the oxygen injection; how big are the lungs; how diluent is injected...

In essence the latest generation of rebreathers are built upon decades of research and refinements: truly standing on the shoulders of giants.

Or, put it another way, we no longer hear people say that X or Y rebreather "should be sold with it's own shovel"**.

One wonders if CE approval's improved or hindered rebreather design. Improved as it forces performance standards, hindered as design variations (improvements?) are very expensive to test thus may slow innovation.



** to dig your grave