Security Sales & Integration April 2023 - 55

ward the two-wire types. Heat detectors may
also be addressable.
With addressable detectors, the exact location
of the detectors is noted at the fire alarm
control unit and this information can be transmitted
to a supervising station. This allows the
dispatch center to advise the responding fire department
of the location within the protected
premises of where the alarm is being generated
from. In some cases, if the signaling line circuit
is not damaged in a fire, it may be possible to
track the progression of a fire's growth through
the location of the activated smoke detectors.
An analog detector may be adjusted for sensitivity,
depending on the environment the
detector is within. The detectors may also be
programed to be more sensitive at night when
no one is within the protected property. This
allows for a quicker response to smoke, while at
the same time reducing the chances of generating
a false alarm.
The trend for detectors, heat and smoke alike,
appears to be moving toward wireless. The remaining
restraints in that regard are power and
battery life and a reliable radio frequency and/
or path that can be used within an occupancy.
Additional Detector Options
For larger spaces, linear smoke detectors can be
used. These are also known as smoke beams.
They work on the same principle as photoelectric
detectors, in which the level of smoke obscuration
is measured by the detector through
a light source (transmitter) and the receiver.
When the level of smoke reaches a predetermined
percentage, the detector will activate.
These detectors can be used in large warehouses,
manufacturing plants, the atriums of a
hotel or office buildings and large open spaces.
The constraints to their use are that there must
be a stable mounting surface for the transmitter,
prism or transmitter/receiver. There also
must be a clear line-of-sight pathway for the
beam to get from the transmitter to the receiver.
If a clear path is not provided, the device
may be subject to unwanted alarms or a trouble
condition if the pathway is totally blocked.
Smoke beams are very useful within a large
atrium in which smoke stratification may come
into play due to the height of the ceiling. In this
case there may be several smoke beams installed
at various levels within the space.
Aspiration detectors are another means of providing
detection. There are now a number of
securitysales.com
manufacturers that provide such a solution in
which a piping system is installed within the
space to be protected. The air within the space
is then drawn into the piping system and the
level of smoke obscuration is measured. These
can be a very sensitive means of detection in
which a very small amount of smoke needs to
be present to activate the detector. Spaces such
as a datacenter or telephone switch room may
use this method of detection. This method of
detection may also be installed within cabinets
and enclosures that contain critical equipment.
During the past several years, combination
and multicriteria detectors have made their way
into the market. A combination detector will be
several detectors combined into one platform,
with independent outputs for each method of
detection (smoke, CO and heat). A multicriteria
detector combines the signal from various
sources and will activate when predetermined
levels are reached, such as smoke obscuration,
CO percentage or parts per million, CO₂ percentage
or parts per mission and heat. A multicriteria
detector can be very stable yet very
sensitive, providing a very early detection of an
incipient fire.
In closing, the designer of a system needs to
take into consideration the environment within
the occupancy, the use of the occupancy, the geometry
of the ceiling, the ambient temperature
of the spaces to be protected, airflow, ceiling
height and size of the space. From this information,
the detector that would provide the best
application should and needs to be selected. SSI
SHANE CLARY, PH.D., has more than
45 years of security and fire alarm industry
experience. He serves on a number of NFPA
technical committees, and is Vice President
of Codes and Standards Compliance for
Concord, Calif.-headquartered Bay Alarm Co.
APRIL 2023 Security Sales & Integration 55
With addressable detectors,
the exact location of the
detectors is noted at the fire
alarm control unit and this
information can be transmitted
to a supervising station.
Smoke beams are
very useful within
a large atrium
in which smoke
stratification may
come into play
due to the height
of the ceiling.
AUREMAR/STOCK.ADOBE.COM
http://www.securitysales.com
Security Sales & Integration April 2023

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