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TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
I
(1) Smoke detectors. Two types of smoke detec-
(d) Flame flicker detector is a photoelectric
flame detector with means to prevent response to
tors are used: ionization and photoelectric. Ioniza-
visible light unless the observed light is modulated
tion smoke detectors contain a small amount of ra-
at a frequency characteristic of the flicker of a
dioactive material which ionizes the air in the
flame.
sensing chamber, thus rendering it conductive and
(e) Infrared detector is a device with a sens-
permitting a current flow through the air between
ing element which is responsive to radiant energy
two charged electrodes. When smoke particles enter
outside the range of human vision.
the ionization area, the detector circuit responds
(f) Ultraviolet detector is a device with a
with an alarm or buzzing.
sensing element which is responsive to radiant en-
(a) Photoelectric spot-type detectors contain
ergy outside the range of human vision.
a chamber that has either overlapping or porous
(2) Sprinkler systems. Protecting the plant
covers of light that allows the entry of smoke. The
from fire frequently requires the installation of a
unit contains a light source and a special photosen-
sitive cell in the darkened chamber. The cell is either
sprinkler system. Equipment consisting of overhead
piping and attached sprinklers connected to an au-
placed in the darkened chamber at an angle differ-
ent from the light path or has the light blocked from
tomatic water supply protects defined spaces and a
it by a light stop or shield placed between the light
variety of hazards. There are four major types `of
source and the cell. With the admission of smoke
sprinkler systems: The wet-pipe system is the sim-
plest and most common. The piping is always filled
particles, light strikes the particles and is scattered
and reflected into the photosensitive cell. This
with water, which begins to flow as soon as the first
causes the photosensing circuit to respond to the
sprinkler opens. Other types are dry-pipe, deluge,
presence of smoke particles in the smoke chamber.
and pre-action systems.
b. Security system. Before the advent of low-cost
(b) Flame detector is a device that responds
to the appearance of radiant energy visible to the
computer multiplexed hardware, security systems
human eye or to radiant energy outside the range of
were simple hardwired alarm systems, providing a
human vision.
minimum level of intrusion detection. Today, the
(c) Photoelectric flame detector is a device
system may be a fully redundant computer-based
which the sensing element is a photocell that either
system interfaced with a redundant looped time-
changes its electrical conductivity or produces an
division-multiplexed communication network for
electrical potential when exposed to radiant energy.
gathering alarm data from sensors and for sending
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