CO alarms....

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Hi, I am wiring up my house for some interlinked mains lithium battery
backed up CO alarms.

I am putting in at least 3, one in the lounge which has a wood burner,
the second on in the main bedroom above the lounge (due to the chimney
stack in the bedroom) and a third one in the loft (due to the chimney
stack in the loft).

Now I have a boiler in the kitchen and a gas hob with 8 rings.

I would like to put a CO alarm in the kitchen due to the boiler but am
concerned that the gas hob may cause nuisance alarms?

The gas hob and the boiler are at opposite ends of the kitchen if that
is helpful as I could position the detector nearer the boiler rather
than the gas hob.

There is a cooker hood above the gas hob but that is currently
recirculating back into the kitchen but I can convert this to extract to
outside. (that will help with cooking smells and stop kitchen steaming
up, and of course take away products of combustion)

What do you all think?

Stephen.

Re: CO alarms....

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Get a canary.



Re: CO alarms....
On Sat, 14 Apr 2012 19:33:41 +0100, Stephen H wrote:

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Possibly a bit OTT (again...)

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Sensible and I think mandatory. Check with the installation
instructions where it needs to be located. CO is heavier than air
unlike smoke...

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Sort of sensible but has the chimney had a liner fitted with the wood
burner? If so I don't think there is much point.

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Why? CO isn't a fire risk and again if the chimeny has been lined
proabably a waste of effort.
 
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A hob shouldn't generate CO. What sort of boiler is it, room sealed?
One near that might not be a bad idea but again check where it needs
to be installed to be effective.

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Do it, irespective of any any alarms. We had a recirulating hood here
when we moved in waste of time. Vented it to outside and the windows
and walls no longer poured with condensation unless one was really
boiling the pasta in an open pan hard, even then it was much less
than with the stupid recirc.

--
Cheers
Dave.




Re: CO alarms....
Dave Liquorice wrote:

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CO is slightly lighter than O2 and the same (as good as) density as N2:

(by atomic weights)
CO = 28
N2 = 28
O2 = 32

(invoking Avogadro's Law)
--
Tim Watts

Re: CO alarms....
On Sat, 14 Apr 2012 21:11:09 +0100 (BST), "Dave Liquorice"

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Way over the top.

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CO is fractionally lighter than air (28.01 grams per mole compared
with 29.96 for air).

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There isn't any point if the fire has been correctly installed.

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Indeed.
Any gas hob will generate some CO, but very little (insignificantly
little) if it is burning correctly.  Certainly not enough to trigger
an alarm.

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The risk from CO is usually caused by protracted failure of something,
either a vent or burner, being able to measure CO content and detect
variation over time  is more useful than a single set point alarm.

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Definitely agree with that - it will also vent the trivial amount of
CO produced by the hob.



Re: CO alarms....
On Sat, 14 Apr 2012 22:52:08 +0100, Peter Parry wrote:

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What ever.  B-)  The point is CO alarms are a little more fussy about
their location than heat/smoke alarms. In an occupied room that may
be subject to CO they ought to be at the same level as ones normal
head height.

--
Cheers
Dave.




Re: CO alarms....
On Sat, 14 Apr 2012 23:20:34 +0100 (BST), "Dave Liquorice"

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Actually they are quite a bit less fussy, but this is more to do with
the different ways CO and fire present a threat.  CO invariably builds
up over time.  Even if a catastrophic failure of a chimney liner
caused a burner malfunction the rate of build up of CO would be
measured in tens of minutes to hours rather than seconds.  In the more
common case of build up of soot or similar increasing CO output the
increase is measured in days to weeks.

Fire on the other hand can develop within a few minutes.  The CO alarm
will work more or less anywhere (although I agree head height is best
if only because it makes it easier to see the reading (and I wouldn't
get one that didn't display the CO level)).

Products of combustion detectors on the other hand must be sited to
catch the first flow of combustion gasses within seconds so siting is
rather more critical. On a ceiling away from walls works well, on a
ceiling near a wall doesn't as the initial flow of gasses won't go
there.

Re: CO alarms....
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There have been a couple of CO deaths in the news recently where
the source of CO was not an appliance in the house, but actually
a neighbour's faulty appliance. So it's probably a good idea to
not be too blinkered by just your own appliances, but also to
consider sleeping areas where you can also be vulnerable to someone
else's CO.

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Agree. Might not like the temperature extremes in a loft either.
If you must have another, put it in another bedroom.

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The grill on a gas cooker is likely to generate most (mainly because
it's usually the most powerful burner, but also because of the nature
of the burner design to throw a horizontal flame some distance.
I believe the room ventilation requirements mean it shouldn't be able
to produce more than 50ppm CO in the room, and a CO detector shouldn't
trigger at that level for hours, and you don't use a grill for hours.

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Again, don't just consider your own gas appliances as sources,
but also neighbours'.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

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