Carbon Monoxide Alarm - Help!

Aug 25, 2012
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Hi all,
My caravan is a 2011 Swift Conqueror 530.
It is fitted with a Carbon Monoxide detector which, until this week, had
just been sitting there quietly in its position on the wall.

In the small hours of Tuesday morning, while we were on holiday in Wales, we
were woken by the sound of the alarm going off. A quick check of the user
information showed that this was not a ‘low battery’ warning but a proper alarm
signal. I didn’t want to wake the people in nearby
caravans and the only way that I could silence the alarm was to remove the
batteries.

No gas equipment was running at the time, or had been for several hours. The
fridge was operating on mains electricity, as was the Alde heating (the central
heating itself was not running, as the thermostat was set to a low figure, just
the water heater was on).

I was a bit puzzled as to the possible source of CO, as I had always
associated it with the incomplete combustion of fossil fuels, and I couldn’t see
how this applied to my situation.

Although I know that the sensible advice is to get outside as soon as an alarm occurs, I
didn’t really feel like doing this in the middle of the night. As neither of us appeared to be suffering from any of the symptoms of CO
poisoning, I opened the windows and the roof light wide to get some
ventilation. We sat there awake for a couple of hours, still feeling ok, and
then went back to sleep.

In the morning, I put the batteries back in the alarm, and all seemed well
again. However, at 1.30 am on Tuesday morning, the alarm went off again. I followed the same procedure as for the
previous night.

I was worried that we may have a serious problem, so I went to a nearby
electrical store and bought another CO detector, this time with a readout of
the CO level in parts per million (ppm). On Wednesday night, both of the detectors were
in use, with the same caravan equipment running again, but there was no further alarm,
and the readout on the new detector remained at zero.

On Thursday, we came home and parked the caravan in the back garden. I
connected a mains hook-up lead to keep the battery charged, as I normally do. We went out for a couple of hours, and when we
returned, we heard the sound of the CO alarm coming from inside the caravan.
The readout on the scale was 140ppm.

This time, the gas was turned off at the cylinder, and the Alde heating
and fridge were also off. The mains electricity was on but the only equipment
running in the caravan was the battery charger and the intruder alarm.

I removed the CO alarm from the caravan and took it indoors, where the
reading fell to zero after a few minutes. I put it back in the van on the following
morning, without altering anything from the previous day, and it has now been
there for about 36 hours, still reading zero.

I’ve read on the internet of instances of hydrogen being produced from
battery charging causing a CO alarm to operate.
I don’t know if that’s happening in my case – and isn’t the battery box
sealed from the van interior anyway?

I’m not sure what’s going on – does anyone have any ideas?
 
Mar 14, 2005
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Hello Mike,
You are right to be wary if an alarm activates, and your actions whilst drastic were sensible. At least you have not simply ignored it.

You are correct in you belief that incomplete combustion causes CO, but it doesnt have to be fossile fuels, its any fuel that contains carbon which most do in some form.
Your actions I think do show there was no actual danger and points to a faulty sensor. Your replecment unit seems to be functioning well.
Now lets consider you situation at home. You had towed the caravan back home. Cars produce CO and it seems quite possible the remnants of the exhaust have entered the caravan whilsttowing which have raised the CO level to the 140 ppm you tells us. So that may have caused the detector to activate.
On allowing the caravan to ventilate after the activation the level has naturally droped
It is possible that some detectors cannot discriminate other gasses and may activate in there presence, For confirmation you need to consult the detectores hand book or contatct the manufacture. You may find some comments on websites.
 
Aug 25, 2012
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Hi Prof John,

Thanks for your reply.

I hadn't thought of the possibility of fumes from the car entering the caravan. However, I've towed the van home many times and, at least as far as I'm aware, the alarm has never activated before. It just seems a bit of a coincidence that it has happened immediately following the two instances on site...

Mike
 
Aug 25, 2010
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Possibly condensation causing the alarm to trigger. My old smoke detector use to false alarm in the winter if I did not have sufficient ventilation. Not sure if the same would happen with a CO alarm but its a possibility.
 
Mar 14, 2005
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Hello again Mike,

Intermittent faults are always difficult to trace and explain, so what ever we suggest is simply conjecture, but some of it may be relevant to your situation.

Now its not entirely clear from the information you have given which alarm activated when you got home, I suspect because you mention the reading on the display it was the new one.

The instructions should tell you at what PPM the alarm should sound.

Perhaps the new one is actually set to be more sensitive than the old one, so if you had previously towed with the new alarm perhaps it would have activated after each journey. - we just don't know.

Two other things do occur to me both of them long shots:-
The first is that many modern central heating boilers utilise horizontal flue systems venting through the walls of houses. There is just a a vague possibility that if your caravan is parked near such a flue, that given the right wind conditions the flue products may be blown towards your caravan. If they enter it might allow sufficient build up to trigger the CO detector.

Secondly and this is less likely but if you park the caravan over a manhole or inspection cover for a sewer or cesspit, and the cover is not properly sealed then perhaps the detector is sensitive to the fumes that might arise.

Whilst such occurrences are rare, I have seen and heard of both instances not related to CO detectors.
 
Aug 25, 2012
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Thanks for your ideas.

Actually, both alarms were activated at home but I only mentioned the new one as it quoted the ppm figure. You wouldn't think it from my rather long initial post, but I was trying to simplify things slightly!

As it happens, the van is parked both next to the flue from the house boiler and over a manhole but the boiler had been turned off while we were away.

Just as an update, the new detector is still in the van, and still reading zero!

Mike
 

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