the UV portion of the spectrum but can ignore UV
radiation from the sun because the upper response
range of the detector falls below the range of UV
radiation that reaches the earth.
Solid-state UV detectors are available, but their
spectral response extends into the sun's UV range
and are not recommended for external use.
UV detectors have an 80 to 90 degree cone of vision.
The UV detector has a fast response time and
usually is not affected by rain, wind, snow, high
humidity, or temperature and pressure extremes. UV
units will produce false alarms if they are exposed
to arc welding or X-ray and gamma radiation. They
can also be blinded by oil film or smoke. UV flame
detectors that are used in dirty and dusty
environments should be equipped with automatic
self-test and self-cleaning devices. The cleaning
device uses a stream of clean air across the lens
surface to minimize the build-up of contaminants.
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UV flame detector shall be of the narrow band response type which operates
on radiated ultraviolet energy and shall be sensitive in the range of
[_____] to [_____] micrometers only. The cone of vision shall be 80
degrees or greater. Each detector shall be completely insensitive to light
sources in the visible frequency range.
2.5.4.4
Combination UV/IR Flame Detector
**************************************************************************
NOTE: Combination UV/IR flame detectors have been
used both inside and outside to detect fires, but
are slower to react than individual units.
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The UV/IR detector shall provide discrimination against false alarms by
requiring both UV and IR flame detection before an alarm is sent. The UV
sensor shall be sensitive in the range of 0.185 to 0.265 micrometers only.
The IR sensor shall be sensitive in the range of [_____] to [_____]
micrometers only. Detectors shall be completely insensitive to light
sources in the visible frequency range.
2.6
NOTIFICATION APPLIANCES
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NOTE: If provided, electrically powered internally
illuminated emergency exit signs shall flash as a
visual emergency alarm in conjunction with audible
emergency alarms. EXCEPTION: Visual alarms devices
that are mounted adjacent to emergency exit signs
can be used in lieu of flashing exit signs.
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Audible appliances shall conform to the applicable requirements of UL 464.
Devices shall be connected into notification appliance circuits. Devices
shall have a separate screw terminal for each conductor. Audible
appliances shall generate a unique audible sound from other devices
SECTION 13850A
Page 22
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