CO2 Monitor and CCR

[iowasnowboarder]

Let me preface this by saying, I am not yet a rebreather diver.

My understanding is that the main problem with CCR is the inability to monitor CO2 levels. If there were a solution to this, could it be electrical, or must it be chemical/mechanical?

 

[caveseeker7]

If there were a solution to this, could it be electrical, or must it be chemical/mechanical?

There is a solution to it, placing a CO2 sensor in the inhalaton side of the loop.
An engineering company in the UK has developed the technology and it is in
military use. Hasn't been made available for recreational dives yet afaik.

 

[iowasnowboarder]

The reason I asked about this is that one of the vendors I deal with professionally (mechanical engineer) has a CO2 monitor that is rougly the size of an altoids tin. It is powered by a 9v battery, and its provides continous monitoring with a digital readout of the CO2 content. It seems to me that this would be exactly what you guys are looking for. Please correct me on this.

 

[caveseeker7]

CO2 monitoring isn't new. Making it work reliably in a rebreather's loop at 100% humidity is.

 

[pipedope]

As I understand it, the problem is getting a CO2 monitor that is reliable in use in a RB that a diver can afford.

I remember that Tom Rose had something in the works and the last I heard was that it was in the patent process and such.

 

[caveseeker7]

I don't know what exactly Tom Rose is working on. There are various ways to measure CO2, like light absorbance oof gas molecules. That one doesn't work because of the hummidity. The CO2 sensor has been implemented and tested. It's just not offered yet publicly.

As far as pricing is concerned, that would probably depend on the volume to a large extend. Most manufacturers turn out rebreathers in fairly low numbers. The company that has developed the CO2 monitor wants to offer it as a complete electronics package (setpoint, deco & CO2). As such it would compete against the Hammerhead (setpoint & deco - $3,000) and Vision upgrade for the Inspiration (setpoint, deco and scrubber gauge - $4,500), which aren't exactly cheap either.

If they can offer it for around $4,000 it should be competitive.

But first the product must be cleared for sport diving use, and CE certifications may be required.

Also, all current electronically controlled CCR manufatcurers either already have upgraded electronics available, standard or on the drawing board.

Evo - standard: setpoint, deco and scrubber gauge
Inspiration - optional: setpoint, deco and scrubber gauge

PRISM - optional deco planned

Meg - optional: Shearwater setpoint & deco

Optima - standard: HH setpoint & deco

Ouroboros - standard: propratory setpoint & deco

So getting a manufacturer to offer the electronics isn't gonna be easy.

 

[Dr. Doug Ebersole]

The inspiration now has a CO2 monitor. I don't dive the unit but I was doing some technical diving on open circuit in Grand Cayman last month with Nat Robb of Dive Tech who was on his Inspiration. He has one of the prototype CO2 monitors in his Inspiration. You may want to contact him or Nancy (the owner) at Dive Tech (www.divetech.com)

 

[caveseeker7]

Doug, the Vision electronics, stock on the Evo and optional on the Inspo do not monitor CO2.

There are temperature sensors (Thermo Stick) in the cannister measuring the various temperatures inside the cannister as the heat front moves along. 'Hot' active areas appear as a dark bar, and as the absorbant gets used up turn into empty rectangles.
The sensors and display are called Scrubber Gauge by APD and is comparable to a fuel gauge in a car.

It's an indicator of the scrubbing process, but by no means of the result of the process.
In O2 terms, it's the contents gauge, not the O2 cell/pO2 readout.

You know the current content, you can estimate the availabilty as long as consumption doesn't change, but you don't know if the CO2 is removed entirely from the loop any more than O2 is added into it in the correct amount.

 

[nigelvh]

Doug, the Vision electronics, stock on the Evo and optional on the Inspo do not monitor CO2.

Agreed. But after listing to Martin Parker's presentation on the 'Pure Inspiration' weekend just gone I was convinced enough to put my money down. It won't protect you from bad packing or miss-assembly but it will give a bad display by the time you have prebreathed it so normal display mean normal operation.

OK. I'd be in the market for a CO2 alarm but that is all we can hope for. When break through starts it is get off the loop time. I've had one run in with CO2 and I'd do a lot to avoid another.

 

[caveseeker7]

When all that Scrubber Gauge talk first started I wrote somewhere that I wouldn't trust it telling me everything is fine, but I would trust the alarm telling me something's wrong.

For me the gauge wouldn't be worth the extra $$, I think, considering its limitations and added cables, seals and power consumption. But the Vision's handset, HUD, cell tracking, data recording and to a lesser extend deco capabilities are major improvements over the original electronics.