Rebreather World - View Single Post - How helpful would a CO2 monitor really be?

Genesis · 10th August 2006, 01:01

I can see two sides to this:

If you get some warning between too-high CO2 and mental incapacity, then it is of value. Definitely.

However, there is anecdotal evidence that it don't work that way in all (or even many) cases. Example - there were a few people killed in a CO2 fire extinguishing discharge accident a number of years ago. They were within ten feet of the door - and safety - when it went off. All evidence suggests that they fell almost literally where they stood, which implies that the blackout occurred essentially immediately. Unfortunately there was nobody near (but outside) who saw it and could thus effect a rescue, nor to report on exactly how fast they fell. (The discharge was not in response to an actual fire.)

Now granted, this was with a CO2 level VASTLY exceeding what you'd get from a breakthrough, but still - its sobering to think of in this way. What's the threshold for that sort of "bad result"? Do we know?

If the sensor serves much as many "idiot lights" do on some cars (e.g. "time to buy a new engine") then in truth you may as well leave the sensor out. Telling me that I've lost consciousness (as I do so) isn't very useful.

On the other hand, if you get a material warning - even if its 5 seconds worth - it could save lives. Most people can perform a bail/switch (especially with a BOV) in that amount of time, provided the warning is unambiguous (different tone or HUD light/sequence)

But if the sensor response is 30 seconds and you only get one breath (6 seconds at 10 resps/min) before blacking out, then the warning tells you that you just got killed - that'd be pretty un-funny.

What can be worse with a system that can work like that is the complacency that it can engender. If people believe they will be warned in time to bail, they may be inclined to push scrubber durations more than they do now.....

The temp sticks are nice BUT they can't necessarily detect channeling or sudden breakthrough. Exhaustion, yes - but that's only one of the potential problems......

10th August 2006, 01:01	#7 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,396	Re: How helpful would a CO2 monitor really be? I can see two sides to this: If you get some warning between too-high CO2 and mental incapacity, then it is of value. Definitely. However, there is anecdotal evidence that it don't work that way in all (or even many) cases. Example - there were a few people killed in a CO2 fire extinguishing discharge accident a number of years ago. They were within ten feet of the door - and safety - when it went off. All evidence suggests that they fell almost literally where they stood, which implies that the blackout occurred essentially immediately. Unfortunately there was nobody near (but outside) who saw it and could thus effect a rescue, nor to report on exactly how fast they fell. (The discharge was not in response to an actual fire.) Now granted, this was with a CO2 level VASTLY exceeding what you'd get from a breakthrough, but still - its sobering to think of in this way. What's the threshold for that sort of "bad result"? Do we know? If the sensor serves much as many "idiot lights" do on some cars (e.g. "time to buy a new engine") then in truth you may as well leave the sensor out. Telling me that I've lost consciousness (as I do so) isn't very useful. On the other hand, if you get a material warning - even if its 5 seconds worth - it could save lives. Most people can perform a bail/switch (especially with a BOV) in that amount of time, provided the warning is unambiguous (different tone or HUD light/sequence) But if the sensor response is 30 seconds and you only get one breath (6 seconds at 10 resps/min) before blacking out, then the warning tells you that you just got killed - that'd be pretty un-funny. What can be worse with a system that can work like that is the complacency that it can engender. If people believe they will be warned in time to bail, they may be inclined to push scrubber durations more than they do now..... The temp sticks are nice BUT they can't necessarily detect channeling or sudden breakthrough. Exhaustion, yes - but that's only one of the potential problems...... __________________ "A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American." http://www.denninger.net http://www.diversunion.org/liability.htm - Fix the Diving Cert racket
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