On Tue, 23 Aug 2011 21:34:17 +0100, ARWadsworth wrote:

Peter Parry wrote:
On Tue, 23 Aug 2011 17:10:10 +0100, wrote:


I have a mains powered - with 10-year lithium backup - interlinked
fire alarm system comprising of 3 off Optical Smoke alarms and 1 off
Heat alarm (for the kitchen)
I changed the 2 Ionisation alarms to optical on the advice of Kidde -
about 3 years ago after sporadic alarms occurred (usually in the early
hours of the morning) when there was no cooking/ironing/smoking or
anything triggering them.

That is rather odd advice, is the building two storey and where are the
alarms located?

Ionisation tends to give earlier warning of the most dangerous night
time slow start fires which emit no smoke in the early stages so are
usually preferred over optical for a sole alarm.

BS5839-6 2004 recommends optical smoke alarms in circulation spaces such
as hallways and landings.

Optical smoke alarms are more sensitive to smouldering fires than fast
buring fires and when used in a circulation space such as a hallway or
landing may give better protection than ionisation detectors if the fire
is some distance away.

Yes, I fitted optical in hallway and on upstairs landing (latter is L
shaped and long so I have one at the stairs end and one at the other end).

Ionisation in living room (two, because there's a deep beam down the
middle).

Heat rise in kitchen.



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