Re: smoke and co detectors

[Robert L Bass <sales@xxxxxxxxxxxxxxxxxxxxx>]

On Sun, 15 Jan 2006 19:52:52 +0800, "someone"
<someone@xxxxxxxxxxxxxxxx> wrote:

> Hi
>
> I hope someone here can help or knows where to look.
>
> Recently I saw some smoke detectors that fitted the majority of their bulk
> into the ceiling space so they were much less obvious - does anyone know the
> ones I am talking about as I cant find them now.
>
> Any problems with these?

Don't know.

> I am also looking for a smoke / co tester for use in the garage - any
> comments on good brands or problems with these?

Yes.  Don't use them in a garage.  Smoke detectors of any sort
should not be installed there.  They need to be located in a
controlled environment (temp / humidity) that is low on dust and
does not routinely have smoke in it.  A garage does not meet
these requirements.

Also, while some people like them, I don't believe you should
combine smoke and CO detection on a single output.  The response
to smoke detection is to alert the family, then check the place
for signs of fire.  If no fire is detected you can reset the
alarm and go about your business.  With CO it is not the same.
The proper response (IMO) is to alert the family, exit the
premises immediately and have the fire department check before
re-entering.

Humans cannot see or smell CO gas.  The only indication that
there is lethal gas accumulating in the house will be that CO
detector.  If you decide everything is OK and go back to sleep
when in fact there is a CO problem you may never wake up.

During the years I operated a small alarm company I had several
real CO events where the homeowners did not believe there was a
problem.  In at least two of those the reason they survived is we
called the fire department in spite of their protestations that
all was well.

In an earlier thread I discussed one of these events.  Another
time a family I protected was having a New Year's party.  They
had numerous guests in their large, brand new (well sealed) home.
The gas furnace was running because it was extremely cold
outside.  The home had two large fireplaces and each had a
roaring fire going.

We had installed four CO detectors -- one in the furnace room,
one on the main level and two on the bedroom level.  All of them
triggered, sounding the alarm and triggering the signal to the
central station.  We called the FD and then rang the house (our
policy for CO alarms).

The homeowner insisted that all was well but that the detectors
were just "going crazy" because everything seemed OK.  When the
FD arrived they brought in a tester and informed the residents
that the house was full of CO gas.  They put out the fireplace
fires, opened several windows and doors and after a while the air
was clear.

The problem, BTW, was the fireplaces.  The flame in a furnace is
a very small fire compared to a fireplace.  The two fireplaces
were drawing so much convective current up the chimney flues that
it was being replaced *down* the furnace flue.  This allowed CO
to pour into the basement.  The forced air heating system drew
some of its air in through a basement return and distributed the
CO throughout the house.

If the CO alarm had been combined with fire the homeowners might
have thought it was a smoke alarm and, finding no fire, dismissed
the matter with catastrophic results.  It is because of several
experiences like this that I don't recommend using combined
smoke/CO detectors.

--

Regards,
Robert L Bass

Bass Burglar Alarms
The Online DIY Store
http://www.BassBurglarAlarms.com