MONTH IN FM
DECEMBER/JANUARY 2020 47
FMJ.CO.UK
HOW VISUAL ALARM DEVICES ENABLE
EFFECTIVE, LIFESAVING EVACUATION
In the event of a fire, saving lives is the highest
priority. Building occupants need to be alerted as
early as possible using alarm devices, so they can
evacuate quickly. It is a mandatory requirement
for audio alarms to be used as an integral part of
the fire detection and alarm system. Visual Alarm
Devices (VADs) are used to supplement audio,
providing an e ective means of alerting and
evacuating occupants.
EN54-23 Standard for Visual Alarm Devices
The Installation of VADs has been mandatory since
January 2014 and with the introduction of EN54-23
the use of VADs has grown considerably. The recent
release of EN54-23 by the European Committee
for Standardisation (CEN) clarifies the use of visual
alarm devices in fire detection and alarm systems
for non-domestic premises.
EN54-23 provides clarity by standardising
requirements, test methods and performance
criteria of VADs and ensures all device parameters
are measured in a uniform manner. Prior to its
release, misinterpretation and confusion over a
particular product’s performance was a common
concern in the industry, since there was no EN
standard in existence for VADs.
Where Visual Alarm Devices are Needed
Regulations and codes recommend that VADs
should be installed in places where audible devices
alone would be
ine ective or
where they are
simply undesirable.
Typical applications
where VADs
should be installed
are areas with
hearing impaired
people, hospitals
or sleeping
areas like hotels,
public assembly buildings, broadcasting studios,
manufacturing sites or where people wear hearing
protection due to high, ambient-level noise.
Important Requirements for Visual Alarm Devices
There are four main requirements each VAD needs
to achieve to be compliant with EN54-23. First is the
illumination level, with a minimum of 0.4 lux in the
area covered by the device. Second is the flash rate,
which should be set at 0.5Hz to 2Hz.
Flash colour is the third consideration and is
dependent on how the evacuation criteria is
defined. Red or white light can be used for a single
stage evacuation, while amber may be used for the
first stage in a multistage evacuation process. Keep
in mind that white light requires a higher power
consumption than other colours, which should be
taken into consideration when the fire alarm system
is designed.
The fourth criteria is the installation category,
which refers to the area illuminated by the VADs.
These are mainly classified by wall category, ceiling
category and open class category. There is also a
distinction between devices for indoor and outdoor
use.
The coverage volume that can be achieved with
VADs today has increased due to advancements
in technology. Depending on the category, the
diameter of coverage ranges between 7.5 meters
and 15 meters. This means less devices are required
to reach the same exposure.
Faster Evacuation with Shorter Pulse Length
In addition to alerting occupants as early as
possible, it is important to quickly foster a reaction
so they understand they must leave the building
immediately. Independent laboratory tests show
the way people react to a VAD is influenced by the
duration of the pulse. Interestingly, the shorter the
pulse duration, the faster the reaction. Consequently
shorter pulse durations of LED VADs will result in
improved attention from occupants.
Less Disruption with Auto-Testing
Regular testing of fire detection systems is necessary
but o en disruptive, especially in buildings such
as hospitals or hotels. The latest VADs available
o er automatic self-test features which minimise
disruption during testing.
Automatic self-tests can be scheduled at any
time and the test duration is typically less than one
second per device, so there is virtually no disruption
to occupants. Additionally, accuracy is high as the
system monitors real physical outputs and not just
electrical simulations.
Full Potential with Fire Risk Assessment
VADs o er a fast and e ective way to alert
and evacuate people during an emergency.
Environmental conditions, ambient light levels and
other factors determine the type and specification
of the devices required. Therefore, it’s advisable to
carry out a Fire Risk Assessment of the area before
applying any system design. This will maximise
the e ectiveness of the system and increase the
potential to save lives.
Author: Anja Schafers, Product Marketing Manager,
Fire Detection, Johnson Controls
www.fireclass.co.uk +44 (0) 161 259 4090 FireClassSales@tycoint.com
/www.fireclass.co.uk
link
