6
SYSTEM VARIATIONS
Where a modification to a system is
made, the standard now refers to it as a
‘Variation’ rather than a ‘Deviation’, as
the latter term implied that the system
was in some way inferior. Note that, in
cases where a variation from the
recommendations is proposed, the
system certificate has to be signed and
agreed by all parties.
RF INTERCONNECTION –
WIRELESS SYSTEMS
Although the previous version of the
document didn’t preclude the use of RF
as a form of interconnecting smoke
alarms, it called for a single final circuit. This
potential confusion has been resolved.
Now, because of the introduction of new
‘wireless’ or ‘radio’ interconnect systems,
Clause 15.5 paragraph b says: “If smoke
alarms and heat alarms are of a type
that can be interconnected by wiring, all
smoke and heat alarms should be
connected on a single final circuit”. This
is clearly intended for hard wired
systems, as a note added to this
recommendation states: ‘This
recommendation does not apply if the
form of interconnection is not capable
of conducting current, e.g. if the means
of interconnection comprises radio
communication rather than wiring.’
OTHER ALARM TYPES
For the first time, BS 5839: Pt.6 now covers
CO fire alarms and multi-sensor alarms.
Heat alarms are given far more
importance, as you will have noted
from the New Build changes above, for
example. Heat Alarms should always
comply with BS 5446: Pt.2.
FALSE ALARM CONTROL
A detailed commentary is given on false
alarm control, which should be studied
as this is probably the major reason that
smoke alarms are disabled by the user.
Among its recommendations are:
• Not using ionisation type alarms in
escape routes
• The use of heat alarms where nuisance
alarms could be a problem – only in
areas other than escape routes
• A high level of maintenance to
reduce the incidence of false alarms
• No automatic connection to the Fire
Brigade, because of the high level of
false alarms generated in the home
ALARMS FOR THE DEAF
AND HARD OF HEARING
BS 5839: Pt.6 now has specific
recommendations to make on the use of
specialist alarms for the deaf or hearing
impaired. Strobes and vibrating pads are
discussed, as are signalling requirements
in daytime rooms. Specific reference is
made to the BS 5446: Pt.3 standard.
