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ARW

On 25/11/2018 18:18, wrote:
On Sunday, 25 November 2018 16:44:42 UTC, Peter Parry wrote:

When you are doing the installation yourself how many detectors you
use is your choice and you can add or subtract them as you wish. In
rented properties or for non-DIY installs it isn't as easy (or as
cheap).

The official guidance is still based upon presumptions from decades
ago when the two primary causes of domestic fires were chip pans and
smokers. Chip pans were usually heated on a hob and when they caught
fire the occupant often picked the burning pan up and ran towards the
door with it. After a bit they realised this hurt a lot so dropped
the pan making sure the fire and fuel were widely spread. Open pans
full of hot oil are less common these days but fires in the kitchen
are still the leading cause of domestic fires. Smokers still occupy
second place but cause far less fatalities because of the rules on
furnishing materials. The usual cause of death was Dad coming home
from the pub, sitting on the settee to light his fag and falling
asleep allowing it to drop down the side of the sofa and igniting the
sofa materials. The cyanide fumes these fires produced usually killed
the smoker before they ever realised there was a fire.

It doesn't pay to rely too heavily on smoke alarms alone, currently
about 20% of mains powered alarms will fail to detect a fire
sufficiently serious for fire service assistance to be needed. For
battery alarms the figure is about 40% (the difference being that
many battery powered detectors have no batteries fitted).

There is always going to be a balance between nuisance alarms and
detection. That balance will vary depending upon the occupants and
their activities. However, that is too complicated for simple
guidance which errs on the side of too many detectors and ignores the
fact that users will disable intrusive alarms. No simple guidance can
factor in that the occupant of one room can only sleep with ear plugs
and may miss an alarm outside their bedroom door or that another is
deaf or that another is a keen but not always effective cook.

Fortunately for DIYers the ideal balance of detectors can be achieved
on a case by case basis. Smoke dynamics and understanding that hot
air rises are easy to research at the superficial level need for
planning detector locations and an effective installation is easier
for a competent DIYer than it is for most professionals as they know
the way the house including occupants work.

I fit a lot more detectors than required for one simple reason. Whatever room/area a fire starts in, if there's a detector in there it's going to alarm much sooner than if there isn't. And time is critical to survival.

Ionisation is the type that detects the fastest on the whole. But if one produces repeat false alarms it needs replacing with something less hairtriggery. Failure to do so results in people ignoring then disabling. The legal requirements fail to address that, resulting in nonfunctioning systems sometimes.

I wonder why Aico one of the UKs biggest manufacturer of smoke alarms
are phasing out their ionisation smoke alarms then?

--
Adam