Electrical Contracting News (ECN) May 2016 | Page 42

SPECIAL FEATURE

FIRE DETECTION & SECURITY

MAKING SENSE
OF FIRE DETECTION
Jeremy Roberts at SONA discusses how sensing technology used and trusted by over 90 per cent of the
UK Fire and Rescue Service is helping drive the mains smoke alarm market towards a simplified alternative.

S

ince legislation came
into force in England
requiring private
landlords to install
smoke alarms on
every storey of their
rented properties, it
has never been more
prevalent to ensure the correct alarm is
used to protect properties and tenants.
However, traditional solutions, such as
ionisation and optical smoke alarms, offer

contrasting benefits that can make correct
specification confusing and difficult.

Call outs
The UK Fire and Rescue Services are
called out to approximately 50,000
domestic fires per annum, leading to almost
500 deaths and 11,000 injuries. From
these statistics it’s quite simple to see the
importance of smoke alarms, meaning
correct selection is absolutely essential.

The two most common types of domestic
smoke alarms used throughout UK housing
stock are ionisation and optical, both using
different methods of detection.

Ionisation
Historically, ionisation smoke alarms have
been the most popular. The smoke alarm
has a small amount of radioactive material
between two electrically charged plates,
which ionises the air and causes current
to flow between the plates. When smoke

enters the chamber, it disrupts the flow of
ions, thus reducing the flow of current and
activating the alarm.
Although ionisation smoke alarms
are very sensitive to small particles of
smoke produced by fast flaming fires,
such as chip pan fires, they do have a
tendency to generate a large number of
nuisance alarms, mostly from toasters,
which can lead to end users removing
the battery or completely removing the
smoke alarm.

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