tmassey
Contributor
Like everything I write, this is long and detailed, and you may not need much of this detail. I use a CO monitor both for continuous CO monitoring of my compressor, as well as ad-hoc checking of tank fills I get elsewhere. This is divided into sections so that you can skip the sections you don't care about, or skip to the next post to get to the details of the unit -- of *course* this is more than 10,000 characters...
For just about as long as I've had a compressor, I've had Carbon Monoxide (CO) monitoring. I use a Nitrox stick, and I wanted a way to continuously monitor my output O2 level, so plumbing in a CO monitor didn't add much to the process. I simply teed off my output just before the PMV and attached it to an old SCUBA first stage, and then used a BCD hose and plumbed it to a cheapo shop air regulator, then through an acrylic flow meter (I use 2lpm) and then across my O2 sensor and into the CO sensor. Easy peasy: I strongly recommend it to *any* compressor operator, Nitrox or otherwise. At the time, I spent no more than $300 or so in parts if you can scrounge any old SCUBA first stage. Well worth it, and it's run great for the past 5 years.
At the time I set this up (2017), there weren't a lot of choices for CO monitoring. I ended up with a Toxi RAE 3, which is a personal monitoring device designed to be worn by people such as miners, who are in a confined space with combustion engines. They have the advantage that they are designed to instantly alert with any exposure to CO, and to do so aggressively. They are also relatively inexpensive. They're not really designed to have air shoved into them from a tube, but if you point the tube at the sensor, it works *just* fine. We don't need precision, we need lights and sirens if there's *any* CO, and I've tested this many times: works great.
Fast forward to this month, when my CO monitor alerted while I was running my compressor. This had happened once before when someone was mowing the lawn, but this time, I couldn't find a likely culprit. After much examining of my intake, compressor temperatures, oil condition, and consulting with a couple of other compressor experts, the consensus was that it was *very* unlikely to be coming from the compressor, and to me it didn't seem likely that it would be coming from the air. Someone asked if it could be the sensor, and of course it could. So, I decided to see if I could get an affordable second sensor, not only to be a double-check but to also sit there and monitor the intake *before* I sucked it into my compressor.
So, I went to the place that most of us go to when we want to buy something we're not going to get locally: Amazon. It turns out there's a lot more options today than 5 years ago. But unfortunately, most of them are useless for our purposes.
First, the obvious ones: Home CO detectors. These won't work: most won't alarm below a rather high number, and won't alarm unless they're at that level for a rather long amount of time. We want instant alert for any detectable level. So Home CO detectors are out.
Second, there are a couple of different designs of handheld monitors, that are sold under several dozen different names, but obviously came out of the exact same assembly line. These had a *very* attractive price ($30-$40) and seemed to do exactly what we want. One type had the sensor in the body (and an on/off switch on the side), and the other had a 14-inch or so metal cable with the sensor on the end. Unfortunately, if you read the writeups *very* carefully (including reviews, or comparing different vendors' listings for the obviously-same item), you find that both of them wont' alarm unless the CO is higher than 30 ppm, which is at least 25ppm too high for us. So they're out too.
So, the cheapo detectors are out. Of course, we can go with the same type I'm already using: the PPE monitor. In fact, why not go with another Toxi RAE 3, seeing as it's worked so well? Well, Honeywell bought them, and it seems that they now want to charge a premium price: $300. And I'm cheap, so if I can find something else, I'd rather do so. The other brand (that I didn't know about until after I bought the TR3) is Sensorcon. They make a few different families of these sensors, which as far as I can tell are just relabeled and use different software. For manual use, the Sensorcon Inspector might work. I'm not sure if it will alarm at near-zero PPM, but I *know* that for me there is a definite shortcoming: you can't program the alarm to less than 35ppm. That's way too high, and seeing as I need it to actively alarm me to an issue when I'm using my compressor, it's out for me. Now, if you're just using it to examine a tank after it's filled, this would be just fine: most O2 sensors don't alert you, either. If you step up to the Pro models (for an extra $50 or so), you *can* change the alarm. If I couldn't find anything better that's what I would do, but I wanted to keep looking.
Compressor CO Monitoring
For just about as long as I've had a compressor, I've had Carbon Monoxide (CO) monitoring. I use a Nitrox stick, and I wanted a way to continuously monitor my output O2 level, so plumbing in a CO monitor didn't add much to the process. I simply teed off my output just before the PMV and attached it to an old SCUBA first stage, and then used a BCD hose and plumbed it to a cheapo shop air regulator, then through an acrylic flow meter (I use 2lpm) and then across my O2 sensor and into the CO sensor. Easy peasy: I strongly recommend it to *any* compressor operator, Nitrox or otherwise. At the time, I spent no more than $300 or so in parts if you can scrounge any old SCUBA first stage. Well worth it, and it's run great for the past 5 years.
At the time I set this up (2017), there weren't a lot of choices for CO monitoring. I ended up with a Toxi RAE 3, which is a personal monitoring device designed to be worn by people such as miners, who are in a confined space with combustion engines. They have the advantage that they are designed to instantly alert with any exposure to CO, and to do so aggressively. They are also relatively inexpensive. They're not really designed to have air shoved into them from a tube, but if you point the tube at the sensor, it works *just* fine. We don't need precision, we need lights and sirens if there's *any* CO, and I've tested this many times: works great.
Fast forward to this month, when my CO monitor alerted while I was running my compressor. This had happened once before when someone was mowing the lawn, but this time, I couldn't find a likely culprit. After much examining of my intake, compressor temperatures, oil condition, and consulting with a couple of other compressor experts, the consensus was that it was *very* unlikely to be coming from the compressor, and to me it didn't seem likely that it would be coming from the air. Someone asked if it could be the sensor, and of course it could. So, I decided to see if I could get an affordable second sensor, not only to be a double-check but to also sit there and monitor the intake *before* I sucked it into my compressor.
Searching For a Detector: Most Won't Work!
So, I went to the place that most of us go to when we want to buy something we're not going to get locally: Amazon. It turns out there's a lot more options today than 5 years ago. But unfortunately, most of them are useless for our purposes.
First, the obvious ones: Home CO detectors. These won't work: most won't alarm below a rather high number, and won't alarm unless they're at that level for a rather long amount of time. We want instant alert for any detectable level. So Home CO detectors are out.
Second, there are a couple of different designs of handheld monitors, that are sold under several dozen different names, but obviously came out of the exact same assembly line. These had a *very* attractive price ($30-$40) and seemed to do exactly what we want. One type had the sensor in the body (and an on/off switch on the side), and the other had a 14-inch or so metal cable with the sensor on the end. Unfortunately, if you read the writeups *very* carefully (including reviews, or comparing different vendors' listings for the obviously-same item), you find that both of them wont' alarm unless the CO is higher than 30 ppm, which is at least 25ppm too high for us. So they're out too.
Sensorcon: Might Work for Checking Tanks
So, the cheapo detectors are out. Of course, we can go with the same type I'm already using: the PPE monitor. In fact, why not go with another Toxi RAE 3, seeing as it's worked so well? Well, Honeywell bought them, and it seems that they now want to charge a premium price: $300. And I'm cheap, so if I can find something else, I'd rather do so. The other brand (that I didn't know about until after I bought the TR3) is Sensorcon. They make a few different families of these sensors, which as far as I can tell are just relabeled and use different software. For manual use, the Sensorcon Inspector might work. I'm not sure if it will alarm at near-zero PPM, but I *know* that for me there is a definite shortcoming: you can't program the alarm to less than 35ppm. That's way too high, and seeing as I need it to actively alarm me to an issue when I'm using my compressor, it's out for me. Now, if you're just using it to examine a tank after it's filled, this would be just fine: most O2 sensors don't alert you, either. If you step up to the Pro models (for an extra $50 or so), you *can* change the alarm. If I couldn't find anything better that's what I would do, but I wanted to keep looking.