Diesel heaters and Carbon monoxide alarms

[slipknot]

I have a diesel eberspacher and a kidde 7co detector in my boat. Other than pressing the test button from time to time the alarm doesn’t make a sound. I must admit that when I run the heater I close up the boat to keep the heat in. I do worry about building up CO and that the alarm doesn’t trigger if the levels do actually get too high. So today I waved it in front of the eber exhaust. Nothing. I also waved it over the lit stove. Still nothing. I appreciate that neither of these tests are very ‘scientific’ but I thought it would have been enough to set it off. So, after searching this forum and googling for a while Ihave a couple of questions.
Will a carbon monoxide alarm be activated by diesel exhaust fumes (ie eberspacher)
Is there a way to create sufficient CO to activate/test a CO alarm

 

[maby]

If you look at the Kidde specification, you'll see that it only reacts after it has been exposed to CO for quite a long time - around 10 minutes for quite high concentrations of CO and as much as four hours for low concentrations. CO poisoning is certainly nasty, but it is a slow process and the toxicity is low compared with many poisons - they don't want to trigger false alarms.

 

[duncan99210]

Remember too that when a stove or Eber is working properly, the the actual concentrations of CO in the exhaust will be low, probably too low to trigger the alarm. It’s when the appliance is not working properly that the exhaust will contain raised levels of CO which could then lead to dangerous concentrations of the gas and triggering of the alarm.

 

[AndrewL]

I'm no expert, but I thought that CO was only generated due to incomplete combustion. I am think that a properly installed system which has a good air intake will not generate CO. I assume that even at the exhaust, there should be very low CO levels.

I've always assumed that the detector is required incase the air intake becomes blocked, it some other defect occurs.

 

[awol]

CO alarm testing can be done by lighting a series of matches or holding a lit candle near the sensor - try not to melt the plastic!

 

[SiteSurfer]

I've had three weekends of frustration with C0 alarms, having self-installed a complete Webasto Evo 4 system - the C0 alarms have been going off constantly overnight with ridiculous levels of C0...

Oddly - the Webasto wasn't on at the time!

I tracked the issue back to my batteries gassing (they appear to be knackered!), in the process I tested the alarm by holding it next to the exhaust skin fitting (on the outside of course!) and confirmed that they do work as I could see the numbers increasing (albeit slowly).

So yes, they do work - only it's worth knowing that they might be alarming for the wrong (right?) reason in an enclosed space if your batteries are within the cabin.

 

[slipknot]

Thanks for the very prompt and helpful replies. I also found a bit more info elsewhere on the forum. http://www.ybw.com/forums/showthrea...-detector-test&highlight=Carbon+monoxide+test
All very good info that helps my understanding and keeps me safe. Thanks again

 

[maby]

I think that a certain level of CO is generated whenever you burn a carbon based fuel, but the levels will usually be pretty low. It is not particularly poisonous in the same sense as something like cyanide - there is quite a lot of CO in cigarrette smoke and smokers are not dropping dead on the spot. CO kills you by blocking your red blood cells ability to distribute oxygen - it binds in much the same way ac CO2, but sticks much stronger. It does dissipate from your blood stream slowly and a short period of CO exposure - even to high concentrations - will not be fatal provided you are then able to breathe uncontaminated air long enough to clear it.

I think that we need to draw a distinction between the exhaust of an Eberspacher and the flame of a gas hob. I would expect that the level of CO in an Eberspacher exhaust is quite high - much the same as a car exhaust - but it is not supposed to be venting into an enclosed space which is occupied. A gas hob or other appliance must be configured to produce far lower concentrations of CO - it is expected that you will have it burning in your galley or kitchen for moderate periods and it should not be producing enough CO to make you ill, far less kill you!

 

[vyv_cox]

I guess that if you really wanted to test in almost real conditions you could partially block the combustion air inlet while monitoring the CO level at the exhaust discharge (I assume you have been testing the one outside the boat?) The reduced air intake should cause an increase in CO/CO2 ratio.

 

[maby]

I guess that if you really wanted to test in almost real conditions you could partially block the combustion air inlet while monitoring the CO level at the exhaust discharge (I assume you have been testing the one outside the boat?) The reduced air intake should cause an increase in CO/CO2 ratio.

True but, as I observed above, a domestic CO alarm is designed to require an exposure of ten or fifteen minutes to trigger - even with quite high concentrations of CO - so you would have to be prepared to stand there holding it in the exhaust flow for quite a while. Don't expect to simply wave it through the exhaust and get an immediate response.

 

[pagoda]

True but, as I observed above, a domestic CO alarm is designed to require an exposure of ten or fifteen minutes to trigger - even with quite high concentrations of CO - so you would have to be prepared to stand there holding it in the exhaust flow for quite a while. Don't expect to simply wave it through the exhaust and get an immediate response.

Given that the combustion air for diesel heaters should not drawn from cabin air , the air blown in and heated is from outside the boat and the exhaust is not vented inside the boat, there is more hazard generally from cooking inside a closed boat than a properly installed diesel heater??

 

[maby]

Given that the combustion air for diesel heaters should not drawn from cabin air , the air blown in and heated is from outside the boat and the exhaust is not vented inside the boat, there is more hazard generally from cooking inside a closed boat than a properly installed diesel heater??

But that is not really the point of this thread, is it? The OP was simply asking how to test a CO alarm and my point is that they are designed to respond slowly, so you cannot expect to blow a gust of even quite concentrated CO over one and have the alarm go off. As far as the relative risks of a diesel heater and a gas hob are concerned, you are not really comparing like for like. On one hand, the diesel heater is burning a heavier fuel and in quite large quantities - one might expect the concentration of CO in its exhaust to be quite high compared with the CO content of the waste air from a hob running on butane. On the other hand, the diesel heater is intended to be a closed circuit system in which the exhaust gases never get into the living area unless there is a serious fault in the device or its installation. The hob is intended to be used within the living space and without any installation fault, the occupants will always be exposed to whatever gas it produces.

 

[VicS]

But that is not really the point of this thread, is it? The OP was simply asking how to test a CO alarm and my point is that they are designed to respond slowly, so you cannot expect to blow a gust of even quite concentrated CO over one and have the alarm go off. As far as the relative risks of a diesel heater and a gas hob are concerned, you are not really comparing like for like. On one hand, the diesel heater is burning a heavier fuel and in quite large quantities - one might expect the concentration of CO in its exhaust to be quite high compared with the CO content of the waste air from a hob running on butane. On the other hand, the diesel heater is intended to be a closed circuit system in which the exhaust gases never get into the living area unless there is a serious fault in the device or its installation. The hob is intended to be used within the living space and without any installation fault, the occupants will always be exposed to whatever gas it produces.

My Fire Angel CO alarm has a "Sensor test " mode which can be selected. It will then sound the alarm immediately it senses more than 50 ppm CO.
In normal operation it will take 60 to 90 minutes at 50 ppm to trigger the alarm.

I test the sensor annually with a burning cigarette or incense stick, using whichever comes to hand, in addition to the weekly alarm test with the test button.

The OP's Kidde alarm does not appear to have such a sensor test facility

 

[Kelpie]

Just to correct something upthread, CO binds to haemoglobin in the same way as oxygen does, so rather than simply suffocating you it actively prevents oxygen from being taken in- hence it is harmful in much lower concentrations than inert gases.

Also, FWIW, my Chinaspacher heater has never set off my CO alarm- but my paraffin fuelled cooker occasionally does.

 

[Momac]

You can get tester gas for CO and Smoke detectors in spray cans
https://cpc.farnell.com/search?st=sleep safe

 

[laika]

My co alarm registers zero in the cabin with my ancient ardic on. To test it I once took it outside and held it near the exhaust. Didn’t take long for it to tell me a different story from inside.

 

[maby]

My co alarm registers zero in the cabin with my ancient ardic on. To test it I once took it outside and held it near the exhaust. Didn’t take long for it to tell me a different story from inside.

Is that an alarm with a digital display? They are a great idea - unlike a fire, CO leaves no detectable signs and dissipates quickly once the source is stopped - as in the heater being switched off. The digital display alarms keep a visible note of the maximum CO concentration they have seen - thus warning you if you have a potentially life threatening fault that has only manifested itself while you were away.

 

[KellysEye]

We had a CO and CO2 alarms on our boat.

 

[maby]

We had a CO and CO2 alarms on our boat.

Not CO2, I suspect.

 

[pawl]

Just as an interesting aside to this thread, I was reading a MAIB investigation report a while ago, into an incident where the crew of a motor cruiser were overcome by carbon monoxide whilst on a trip. Happily all survived, the expert witness looking into the cause stated that the diesel heater, which had been running at the time, would not produce sufficient carbon monoxide to cause a problem.