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Old 31-08-2008, 08:03   #1
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CO2 Detector with Alarm

Where can I find a battery-operated CO2 (carbon dioxide) detector with alarm? I do NOT want a CO (carbon monoxide) dector. There are dozens of those. Even the companies who allegedly specialize in this sort of thing don't appear to know the difference between CO and CO2, and when you chase down a link advertising a CO2 detector it invariably turns out to be a CO detector or smoke alarm.

Help, please.
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Old 31-08-2008, 08:43   #2
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Curmudgeon,

I'm really curious! What kind of application do you have for a CO2 monitor?

The things are darned expensive--here's the cheapest (US$365) I found by Googling: http://user876851.wx9.registeredsite...gory_Code=CO2M
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Old 31-08-2008, 13:31   #3
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I am really curious about this as well, I have wracked my brain, and cant think of an application.
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Old 31-08-2008, 14:31   #4
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Dry ice in the refer?
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Old 31-08-2008, 15:30   #5
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My understanding is that CO2 can build up in any improperly vented space, such as a closed cabin. Would a CO detector always be adequate protection against an improperly vented heater?
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Old 01-09-2008, 01:06   #6
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Just get two CO detectors and cut one in half...
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Old 01-09-2008, 02:57   #7
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We fitted an LPG detector but I can't think of any reason for a CO2?
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Old 01-09-2008, 04:33   #8
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Venting vs Ventilation:
A CO detector is used to warn of the products of combustion, such as occurs with an improperly vented appliance (chimney) or incomplete combustion.
A CO2 detector warns of a carbon dioxide buil-up, such as occurs from drawing combustion air from the living space whilst not replenishing it, or from too many people breathing the inside air - both a ventllation issue.
Which type of condition do you wish to monitor & alarm?
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Old 01-09-2008, 07:20   #9
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Originally Posted by GordMay View Post
A CO2 detector warns of a carbon dioxide buil-up, such as occurs from drawing combustion air from the living space whilst not replenishing it

Sorry Gord, this is a bit of a pet-peeve of mine, so I have to speak up with a clarification.

People often mis-understand the mechanics of using a natural-draft heating appliance, so I would like to add a distinction here.

Often, people think you can "use up oxygen" or create a situation such as you mention above in the quote I snipped by using a natural draft heater (wood stove, Dickinson diesel, etc...)

It is *not* possible for a natural draft stove to operate in a way that would "use up" oxygen in a room. In fact, unless you can smell the wood or diesel smoke in your cabin, the appliance cannot be operating in such a way that the air is not "replenished."

If smoke is coming out of the chimney and there is no smoke in the cabin, the stove is *by definition* replenishing the air in the cabin at a rate equal to what is coming out of the chimney.

Call it "conservation of air" if you will.

What happens is that if your stove is lit and running, it is drawing air into the combustion chamber. Why? Because the chimney pulls air from combustion chamber, causing the combustion chamber to pull air from the room. The air pulled up the chimney has to be replaced by air in the room. And... just like the air in the combustion chamber is replaced by the air in the room, the air in the room is then replaced *at the same rate* by air coming in through cracks/vents. If no air were being replenished in the cabin, the stove would:

1) Not light at all or go out

2) Emit smoke throughout the room in large quantities, alerting you to a problem (this would be as if you just burned the diesel or wood on your salon table without a stove)


In the case of a natural draft heating appliance behaving this way (if say, the chimney were plugged with a cork), the product emitted in the room would indeed be CO. You would find a dangerous CO buildup, not a dangerous CO2 buildup.
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Old 01-09-2008, 09:06   #10
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Well, based on Capt. Sully's response (and others) I'm not going to worry about CO2, but I'll be sure to have a couple of CO detectors with fresh batteries in my new boat, which has a propane stove and cabin heater. I know it already has a couple of propane sniffers.

The reason for my original question was that I've done a fair amount of winter hiking, and one hears the stories of people going to sleep with a Svea running in an improperly vented tent (such as one covered with snow) and not waking up. I had thought it was the CO2 concentration that killed them, but maybe it was CO.
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Old 01-09-2008, 10:46   #11
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Originally Posted by Curmudgeon View Post
Well, based on Capt. Sully's response (and others) I'm not going to worry about CO2, but I'll be sure to have a couple of CO detectors with fresh batteries in my new boat, which has a propane stove and cabin heater. I know it already has a couple of propane sniffers.

The reason for my original question was that I've done a fair amount of winter hiking, and one hears the stories of people going to sleep with a Svea running in an improperly vented tent (such as one covered with snow) and not waking up. I had thought it was the CO2 concentration that killed them, but maybe it was CO.
The Svea incidents happen because it does not have a chimney.

Using one of those in the cabin/tent would be akin to lighting a pile of wood or diesel on your salon table and hoping you don't die from CO (or in that case, using up oxygen, too).

After years of experience heating my boat with a wood stove, and briefly with a Dickinson, I can assure you it is the chimney that makes all the difference. Since the Svea has no chimney, it is just like using the galley stove (which also has no chimney).

The galley stove is a surprisingly large emitter of CO (and some CO2 as well as use of O2, but that's not what kills you first). We find that our CO alarms always go off if we don't open up the boat completely when cooking in the winter on the galley stove. For this reason, we do most of our winter cooking on the wood stove.

The galley stove is far more dangerous to life than a natural draft (aka with a chimney) heating device. The Svea is basically the equivalent of a galley stove in a tent.


The key is to picture the air flow... your exhaust gasses should all be going outside the boat (via chimney in my example). If they are not, you are going to create CO (and also a little CO2 and use up a little O2), but it's the CO that kills you.

Now, having a propane heater makes things just a little more challenging because propane doesn't smell bad when it backs up like a wood smoke or diesel smoke. You won't have that extra warning of smelling a little smoke to remind you that something isn't right with your air flow. Some things to be sure of:

1) CO detectors (two is great) are a must

2) Is there an adequate vertically rising chimney with no more than two 90 degree bends in the pipe?

3) Is the chimney of adequate height?

4) Is there a proper "charlie noble" or "smoke head" attached?

The above will greatly reduce the chances of the propane exhaust baking up.

However, you still need to be careful to have enough venting (cracks in companionway, etc...) to keep up with the draw of the chimney. In most cases boats do, but be sure this is your case. If not, you will have to open up a vent here and there to get air moving.

Also, avoid creating a low-pressure situation in your cabin by opening a port that is downwind on a windy day. This would serve to suck air out of the port, out of the combustion chamber, and *down* the chimney. Exactly what can cause you to get CO in the cabin.

Propane will take more vigilance than wood or diesel since you can't smell it backing up.

Multiple CO detectors would be my choice as well if I were heating with propane.

Either that, or one of the propane heaters that is sealed off from the cabin entirely, drawing its own combustion air in through a dedicated vent, and exhausting its fumes through another dedicated vent.

But, to be completely honest, I would be nervous heating with propane and a natural draft stove because there is no warning that it is backing up aside from your CO detectors. (just a personal feeling... many do heat with propane)
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Old 01-09-2008, 10:51   #12
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Carbon Dioxide, CO2, is a suffocant and not poisonous. A suffocant simply means that it displaces oxygen. We breath CO2 all the time. We exhale CO2 as a waste product of respiration.

Carbon Monoxide, CO, is poisonous because it converts haemoglobin and myoglobin to carboxy-haemoglobyn, which is ineffective at carrying oxygen to the body.

CO2 has no effect on the body other than displacing oxygen. Breathing C02 is as dangerous as breathing Nitrogen, which we do with every breath.

So long as you are breathing a normal amount of oxygen (21%) with every breath and not breathing anything poisonous then you will be fine.
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Old 01-09-2008, 15:33   #13
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I agree completely with David and Sully but add that -

I think part of the trouble is that a great number of people think that CO2 is poisonous (which as pointed out, it is not). I think that belief is also in the minds of many of the non scientific with respect to their concern about claimed CO2 global warming; they see CO2 as a poison being added to the atmosphere, which of course it is not.

But the reality is that if one was to sufficate from a lack of oxygen in the air due to combustion, respiration, etc using it up the predominent gas left in the "air" would be nitrogen by far so it would be the main sufficulting "culprit" if one was going to place blame on one gas or the other.
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Old 01-09-2008, 15:50   #14
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I agree completely with David and Sully but add that -

I think part of the trouble is that a great number of people think that CO2 is poisonous (which as pointed out, it is not).
Well yes, it is, sort of. You may find the following link interesting: CO2 poisoning (Steve Harris)

However, the author concludes (along with just about everyone here) that in virtually all practical scenarios, the CO will get you before the CO2 comes into play.
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Old 01-09-2008, 16:54   #15
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Well if you are going to describe gases that can cause narcosis as "poisonous" then nitrogen is also a "poison" (which is is also not classed as being) as under some circumstances it too can cause narcosis (mainly hyperbaric as is well known to divers).

Furthermore oxygen can also be regarded as "poisonous" (which it also is not classed as being) if you regard the effects from breathing it at an elevated partial pressure (such as may happen in gas mixtures - "oxygen toxicity syndrome") as "poisoning" - results in seizures, cell and nerve damage, etc.

'Tis a dangerous world for those of us that worry too much .
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