Seymour Fisch
Contributor
Reading the Accidents and Incidents forum over the past year or so convinced me that I definitely wanted to get a carbon monoxide analyzer eventually. (What I was really hoping for was that these would become as common as oxygen analyzers, such that I could borrow one at any shop or dive op whenever I needed one, as I don't dive that frequently, but this hasn't happened yet.) An upcoming trip to a remote location in a developing country pushed me over the edge, so I ordered the Sensorcon Carbon Monoxide Detector Meter with the (recently discontinued) Scuba kit. I figured I'd share my first impressions, as well as ask a few questions of other more experienced users.
(tl;dr version -- the meter seems great, but without a flow restrictor, you don't get consistent readings. The discontinued Scuba kit is unimpressive. I think it'll work for a quick/sloppy check for dangerous CO levels, and it's less than half the price of the alternatives, but if the Analox meter were still available, I'm guessing I would have been happier with that.)
The kit comes in a black plastic case. From the webpage photos, I had imagined something like a Pelican case, but the actual case isn't nearly as sturdy -- I can flex it with my bare hands. It was also bigger than I was expecting, about 10"x9"x3" (25cm x 22cm x 7 cm roughly), so it'd fit in my dive bag, but it takes up more space than I'd like. This was a disappointment. The case was nicely foam filled and protected the contents nicely during shipping. I'm thinking for actual use, I might try to get away with fewer components, and with the meter in a much smaller Pelican case.
Inside, the kit included the CO meter itself, which is compact and felt like a high quality product. There was also a Yoke-to-DIN adapter, two screw-in fittings, and a couple feet of plastic hose with a T-fitting, a pressure relief valve, and a little plastic nodule that I assumed was some sort of flow restrictor. These components seemed rather cheap and kludgey. There was also a nicely printed, but very brief user manual and quick start guide (a few 3"x4" pages), and two pages of 8.5x11 color photocopied instructions for the Scuba kit. The Scuba stuff really felt like an afterthought, and Sensorcon has apparently discontinued sales of the kit.
The meter felt very sturdy, and it's supposedly waterproof (I think only splash proof, not immersion, and certainly not depth rated). It has a very sturdy locking belt clip on it, which looks removable (and I'll likely remove to make it more compact). It comes pre-calibrated, and you're supposed to recalibrate every 6 months. You can calibrate it yourself with 50ppm bump gas, or send it back to the company. It's the same meter they sell for home and furnace inspections, etc.
Following the assembly instructions for testing a tank, the process was easy, but much more cumbersome than the Analox nitrox analyzer I have used before. You screw the DIN fitting into the yoke adapter, twist on the plastic hose, then insert the other end into the meter, attach the yoke to the tank, turn on the meter, and just barely open the tank valve. According to the supplied instructions, "When you hear or feel air escaping from the open end of the white air relief value [sic], you have opened the air tank valve sufficiently to take a gas measurement." More on that in a moment.
The meter is very sensitive and responds fast. In my office, I was getting around 2-3ppm. Walking outside, away from traffic, I would get 1-2ppm, or down to 0 on a particularly clear and windy day. Holding it near my car exhaust for a moment immediately set off the alarm, with the reading skyrocketing. The first time I tried it in my dive shop, however, it was showing around 20ppm CO in the ambient air, but this was believable, as the shop is located below ground, with several fast-food outlets nearby, grilling burgers and such. However, when I hooked it up to some tanks and tested them, I was getting very high readings, that varied wildly depending on how much I opened the tank valve, and these were going well over 100ppm. The shop manager showed me their most recent quarterly air inspection report, which passed easily, with <2ppm CO. We tried three different tanks, all with crazily high readings that changed considerably with slight changes to the valve opening. I figured the "flow restrictor" must be defective and emailed customer service.
Customer service was very prompt, very friendly, but basically said that that was just the way the meter worked, and that there is NO flow restrictor. The CSR didn't tell me what the little plastic capsule inline in the tubing does, but it looks like it might just be a little dust filter or something. She said that the calibration is for 0.5l/minute, that the meter is extremely sensitive to flow rate, and that if any air escapes from the overpressure valve, I'm definitely opening the valve too much. (So much for following the supplied instructions...)
Back to the dive shop again, by just barely cracking the valve the tiniest amount, I could get the readings down to about 5ppm. Unfortunately, I could easily get the readings to vary between 5 to about 15ppm by varying just slightly how little I opened the valve. So... without buying an expensive flow restrictor, I don't see any way to get repeatable, accurate CO measurements of tank air.
Conclusion: the meter itself is a neat, high quality product, at a great price, but it's not really well-tailored for use as a scuba tank analyzer. It'd be really great if Sensorcon, or a third party, could come up with a way to make this meter easier to use and more repeatable. E.g., I'm guessing that a little dome that fit over the sensor input, with a small orifice to pass through a bit of gas, would do the trick. Even as-is, though, for my purposes, it's probably good enough: I'm pretty sure it reads high, so I'll try to test tanks by opening the air as little as I can, and if I get a reading of, say, 20ppm (the US OSHA limit for commercial diving, which is much higher than e.g., British limits) or less, I'll use the tank, and if I get a really high reading, I'll reject it. The meter with the discontinued scuba kit was less than half the cost of the competing OxyCheq meter (and discontinued Analox meter that everyone loved), and now with no scuba kit, the meter itself is only $120, so not too bad. I haven't used the other products, so I don't know how much better they might be.
Questions:
For other users of this meter, any suggestions on how to get reliable readings? Maybe vent gas into a little plastic baggie?
Alternatively, any suggestions on making this easier to use? I'd hate to be futzing with all the kit contents on a dive boat. If I'm just using this for a rough check, could I get away just blowing some gas into the meter straight from the tank valve?
Does anyone know any source of small amount of 50ppm CO bump gas in Canada (ideally Vancouver or Canadian mail-order)?
(tl;dr version -- the meter seems great, but without a flow restrictor, you don't get consistent readings. The discontinued Scuba kit is unimpressive. I think it'll work for a quick/sloppy check for dangerous CO levels, and it's less than half the price of the alternatives, but if the Analox meter were still available, I'm guessing I would have been happier with that.)
The kit comes in a black plastic case. From the webpage photos, I had imagined something like a Pelican case, but the actual case isn't nearly as sturdy -- I can flex it with my bare hands. It was also bigger than I was expecting, about 10"x9"x3" (25cm x 22cm x 7 cm roughly), so it'd fit in my dive bag, but it takes up more space than I'd like. This was a disappointment. The case was nicely foam filled and protected the contents nicely during shipping. I'm thinking for actual use, I might try to get away with fewer components, and with the meter in a much smaller Pelican case.
Inside, the kit included the CO meter itself, which is compact and felt like a high quality product. There was also a Yoke-to-DIN adapter, two screw-in fittings, and a couple feet of plastic hose with a T-fitting, a pressure relief valve, and a little plastic nodule that I assumed was some sort of flow restrictor. These components seemed rather cheap and kludgey. There was also a nicely printed, but very brief user manual and quick start guide (a few 3"x4" pages), and two pages of 8.5x11 color photocopied instructions for the Scuba kit. The Scuba stuff really felt like an afterthought, and Sensorcon has apparently discontinued sales of the kit.
The meter felt very sturdy, and it's supposedly waterproof (I think only splash proof, not immersion, and certainly not depth rated). It has a very sturdy locking belt clip on it, which looks removable (and I'll likely remove to make it more compact). It comes pre-calibrated, and you're supposed to recalibrate every 6 months. You can calibrate it yourself with 50ppm bump gas, or send it back to the company. It's the same meter they sell for home and furnace inspections, etc.
Following the assembly instructions for testing a tank, the process was easy, but much more cumbersome than the Analox nitrox analyzer I have used before. You screw the DIN fitting into the yoke adapter, twist on the plastic hose, then insert the other end into the meter, attach the yoke to the tank, turn on the meter, and just barely open the tank valve. According to the supplied instructions, "When you hear or feel air escaping from the open end of the white air relief value [sic], you have opened the air tank valve sufficiently to take a gas measurement." More on that in a moment.
The meter is very sensitive and responds fast. In my office, I was getting around 2-3ppm. Walking outside, away from traffic, I would get 1-2ppm, or down to 0 on a particularly clear and windy day. Holding it near my car exhaust for a moment immediately set off the alarm, with the reading skyrocketing. The first time I tried it in my dive shop, however, it was showing around 20ppm CO in the ambient air, but this was believable, as the shop is located below ground, with several fast-food outlets nearby, grilling burgers and such. However, when I hooked it up to some tanks and tested them, I was getting very high readings, that varied wildly depending on how much I opened the tank valve, and these were going well over 100ppm. The shop manager showed me their most recent quarterly air inspection report, which passed easily, with <2ppm CO. We tried three different tanks, all with crazily high readings that changed considerably with slight changes to the valve opening. I figured the "flow restrictor" must be defective and emailed customer service.
Customer service was very prompt, very friendly, but basically said that that was just the way the meter worked, and that there is NO flow restrictor. The CSR didn't tell me what the little plastic capsule inline in the tubing does, but it looks like it might just be a little dust filter or something. She said that the calibration is for 0.5l/minute, that the meter is extremely sensitive to flow rate, and that if any air escapes from the overpressure valve, I'm definitely opening the valve too much. (So much for following the supplied instructions...)
Back to the dive shop again, by just barely cracking the valve the tiniest amount, I could get the readings down to about 5ppm. Unfortunately, I could easily get the readings to vary between 5 to about 15ppm by varying just slightly how little I opened the valve. So... without buying an expensive flow restrictor, I don't see any way to get repeatable, accurate CO measurements of tank air.
Conclusion: the meter itself is a neat, high quality product, at a great price, but it's not really well-tailored for use as a scuba tank analyzer. It'd be really great if Sensorcon, or a third party, could come up with a way to make this meter easier to use and more repeatable. E.g., I'm guessing that a little dome that fit over the sensor input, with a small orifice to pass through a bit of gas, would do the trick. Even as-is, though, for my purposes, it's probably good enough: I'm pretty sure it reads high, so I'll try to test tanks by opening the air as little as I can, and if I get a reading of, say, 20ppm (the US OSHA limit for commercial diving, which is much higher than e.g., British limits) or less, I'll use the tank, and if I get a really high reading, I'll reject it. The meter with the discontinued scuba kit was less than half the cost of the competing OxyCheq meter (and discontinued Analox meter that everyone loved), and now with no scuba kit, the meter itself is only $120, so not too bad. I haven't used the other products, so I don't know how much better they might be.
Questions:
For other users of this meter, any suggestions on how to get reliable readings? Maybe vent gas into a little plastic baggie?
Alternatively, any suggestions on making this easier to use? I'd hate to be futzing with all the kit contents on a dive boat. If I'm just using this for a rough check, could I get away just blowing some gas into the meter straight from the tank valve?
Does anyone know any source of small amount of 50ppm CO bump gas in Canada (ideally Vancouver or Canadian mail-order)?
, and indeed, the meter alarmed very quickly, then cleared very quickly (and the display actually went negative for a couple seconds), returning to 0-2ppm.
