Would you trust the scrubber monitor

Janos

I'm currently debating which breather to go for (but it won't be for a few months) One option is the Evolution, which, as I'm sure you're all aware, comes with a two hour rated scrubber, and a 'temp stik' scrubber monitor.

I think that two hours of scrubber is not quite enough for a days diving, (I'm a cautious sort of person), but I would be suprised if all the scrubber had been used up after two dives.

So, if you'd dived the unit for two hours, but the scrubber monitor showed that the scrubber was only half-used (or half-unused depending on your outlook on life) would you dive again on the same scrubber?

Laters,
Janos

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schford

Could we get an other option - eg It depends on the type of diving I am doing?

The reason I say that, is that if you had used say 50% of your scrubber material and the guage showed 50% remaining you would NOT be able to dive for the same length of time.

The reason for this is that the deeper you dive the more molecules of gas will be in the loop and consequantly going through the scrubber. What this then means is that the reaction front in the scrubber eg the 'depth' of scrubber material being used to remove the co2 from what you exhale will vary with depth.

eg Say at 10m depth we might only use 1cm of scrubber material to remove the co2 but at say 50m depth we might use 5cm of scrubber material.

Now lets just imagine the guage showed we had the equivalent of 5cm of scrubber material left unused - if we did a shallow 10m dive then we could dive on it for a long time, however if we went down to 50m then we would have zero dive time as co2 would start breaking through as the scrubber material left unused would not be able to remove it all.

Hope that makes sense.

Stuart

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Janos

Perfect sense

But I guess my question is more how much do you trust the scrubber monitor?

Ie would you use an Evolution scrubber for more than 2 hours if the scrubber monitor indicated that you could (taking into account the depth of the raction front etc). Or do you not trust the scrubber monitor that much?

The reason I ask is that I normally do two dives a day, and don't want to repack the scrubber between dives. I think I would also start to get close to the two hour limit quite regularly, which I'm slightly uncomfortable with as I'm quite risk-averse when it comes to rebreathers!

If I can use the scrubber monitor to safely extend the scrubber duration to (say) 2.5 hours, then the Evolution sounds like it will be up to the job. If the 2 hour limit is cast in stone, then I think I'd look at the Inspiration.

Laters,
Janos

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peter

It cant be so, look at the testing 1,6 liters CO2/min… Can you produce that?

When I do many dives to around 40-50 meters, I use the scrubber on my Inspiration for 3 dives at a total time of 90 min each = 4,5 hours in cold waters. If I do deeper dives, I change more often.

But its your live, your choice.

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Peter

schford

I think I would probably trust the scrubber guage within reaon - as Peter says you are not going to be producing 1.6l of Co2 per min probably nearer 1l per min so thats a 60% safety margin also the water temperature you're diving in will probably be higher than CE testing so thats another safety margin...

Although you need total faith in your packing ability as the guage will never detect chanelling from a poor pack...

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Bailout and Kit Management account for Murphy's Law

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caveseeker7

I've got an e-mail from Martin Parker saying that the monitor is to be trusted and is failsafe. I got it in reply to an e-mail I send in regards to two Evo students all exitedly reporting 4-5 hours of dive duration/fill during their Evo training and certification dives. I found that rather hard to believe not that it's possible, they dove in warm Mexican waters to 20m - 25m, but that it would be done during traininng. Jetsam, ISC and SMI would probably pull the instructors ticket for doubling the factory rated dive time.

Would I trust the gauge?
Not inicially, and never entirely. It monitors a process, not the result.
So dangerous levels of CO2 in the loop, as well as inside the diver, are possible, and possible undetected. So I would slowly and gradually extend my dive time to where the gauge is, basing it on my experiences as I go along.

I would trust it to actually show a problem when the alarm sounds, and would trust it in that I wouldn't dive past 'absorbing process stopped' indication.

For deep dives I agree with Stuart, don't start on used sorb.
Sorb is cheap in comparisson to what you may pay when you get a CO2 hit.

Janos

Ok. This seems encouraging. I will try and nobble AP at the Dive Show and see what the 'official' line will be.

Laters,
Janos

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Mark Chase

Whats the point of having it if you dont use it?

Yes i would definatly trust the simplicity of the temperature stick to monitor the working front in the scruber and my own brain to decide when enough is enough. I watched one of our group pushing his scruber on the Insperation to 6.0 hours in the red sea last week and he was doing it blind. I talked to other relitavly new CCR divers and they were already talking 4.0 hours as acceptable. Its amazing how quickley you get confident with the thing. I think a lot of the divers doing 6-10 hours on the scrubber are making us newbys think 4-5 must be no problem

I would rather have the analisis of the chemical reaction in the scrubber to go on than just guess it.


ATB

Mark Chase

dalegray

Any information given to you by a computer neads reading with a pinch of salt, especially if your life depends on it. We were all taught at MOD 1 to interperate what our hand sets were telling us and not to rely on the info what is diferent about the scubber monitor?

I would fall bettween the 2 poll options, I would take it past the 2 hour on a single dive, but if going in for dive 2 I would change the scrubber if I had the oportunity.

My position would be to use the monitor not to rely on the monitor

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Janos

Hmm.

Well a bit more on this. I spoke to MP and a few other at the show. The official line is that the scrubber is only rated for 2 hours and any more then that you do at your own risk. However 'reading between the lines' (I really hate doing this) then they are quite happy for you to extend the scrubber a bit beyond 2 hours if the scrubber monitor says you can.

Also, apparently the shape of the reaction front is a cone - it extends more down the edge than in the centre. The monitor has some (crude but conservative) calculations to estimate this.

Laters,
Janos

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