RE: [PSUBS-MAILIST] Which gases to detect?

Agreed 100%. I've had a 10,000 ppm unit on a shelf for years, which is intended for monitoring buildings. The other day I wired it up and did a quick test. With no scrubber at all, just closing the air in the hatch, it took only 2 minutes to reach 10,000 ppm. With two people as Snoopy now carries, an instrument that reaches the top of its scale in one minute is obviously not going to be useful. So I am looking for a 5% range alternative. Unfortunately the purchase I was referring to below fell through, because I found out yesterday that the vendor had given me a price on the phone that turned out to be in error. Another consideration is the ruggedness, in particular resistance to excess humidity. I once bought a pair of Ohmeda oxygen meters, which are hospital equipment. They would appear to be exactly what you want on a sub. They are powered by dry cells, have a nice big backlit display, and both high and low alarms. But the first one lasted half an hour in the sub and simply went dead. The second did the same after only a few dives. I put together one working unit from the leftovers of the two, for now, but I am looking at something more moisture resistant. The nice thing about these little personal meters designed to be worn on your belt is that they're built to go into harsh environments, not a hospital room like fragile medical equipment.

I'll let you know what I settle on in the end. It's very easy to find good stuff. It's hard to find good stuff at affordable prices!

Alec

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan James
Sent: Monday, April 25, 2011 5:48 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Which gases to detect?

Hi Alex,

I bought a cheap CO2 monitor wich only measures up to 10,000 ppm or 1%.

I should be keeping levels well below this & will surface if I go any higher.

NASA has a limit of 3% exposure for 1 hour, & in hind sight I wish I'd bought

something with a greater range so I could push the limits if necessary or if

I was entrapped, estimate when I would need to jump ship.

So I'd advise checking it's range if you haven't already.

Regards Alan

----- Original Message -----

From: Smyth, Alec

To: personal_submersibles@psubs.org

Sent: Tuesday, April 26, 2011 6:35 AM

Subject: [PSUBS-MAILIST] Which gases to detect?

I've been looking into gas monitors, and have found what I think is a good one for the lowest cost. What I'm interested in monitoring is O2 and CO2, but the instrument monitors four gases in total. The question then is, if I'm going to get two extra gases monitored for the same price, do any of the available combinations present some advantage for a sub? Here are the "extra" gases to choose from:

- Carbon monoxide and hydrogen sulfide
- Ammonia and sulfur dioxide
- Ammonia and chlorine
- Carbon monoxide, ammonia
- Carbon monoxide, sulfur dioxide
- Carbon monoxide, chlorine
- Hydrogen sulfide, ammonia
- Hydrogen sulfide, chlorine
- Sulfur dioxide, hydrogen sulfide

I'm thinking I could always use the carbon monoxide in my home when checking for furnace leaks, and was it not chlorine that is produced when sea water comes in contact with batteries? In that case monitoring for chlorine might be useful in a sub that has battery pods that communicate with the cabin.

For those interested, here is the manual describing this instrument: http://www.canarysense.com/crm_uploads/honeywell_analytics_impact_gas_detector_user_manual.pdf

Thanks,

Alec

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