Bosch D281A User Manual
Fire Alarm Systems | D281A Ionization Smoke Detector
D281A Ionization Smoke Detector
www.boschsecurity.com
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Removable, non-polarized, 24 VDC head is easy to
install, clean, and service
install, clean, and service
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Compatible with assorted low-profile, tamper-
resistant, two-wire and four-wire bases
resistant, two-wire and four-wire bases
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Dual chamber design
The D281A Ionization Smoke Detector is UL Listed. It
detects smoke particles while tolerating conditions of
extreme humidity, temperature, vibration, and
electromagnetic interference. Use the D281A Detector
in applications such as plenum areas or raised
compartments beneath floors.
detects smoke particles while tolerating conditions of
extreme humidity, temperature, vibration, and
electromagnetic interference. Use the D281A Detector
in applications such as plenum areas or raised
compartments beneath floors.
System overview
The D281A Ionization Smoke Detector uses current
flowing in the ionized chamber to measure smoke
particle levels. When the difference in current between
the two chambers exceeds the alarm threshold, the
D281A Detector signals an alarm.
flowing in the ionized chamber to measure smoke
particle levels. When the difference in current between
the two chambers exceeds the alarm threshold, the
D281A Detector signals an alarm.
Functions
Dual Chamber Design
The D281A Detector has an inner chamber and an
outer chamber. The inner chamber is sealed and
provides a controlled current measurement. The outer
chamber has a screen that filters out dust and deters
insects while still allowing smoke particles to enter. An
increase in smoke particles causes a decrease in
current. The current measurement in the outer
chamber fluctuates according to the volume of smoke
particles.
outer chamber. The inner chamber is sealed and
provides a controlled current measurement. The outer
chamber has a screen that filters out dust and deters
insects while still allowing smoke particles to enter. An
increase in smoke particles causes a decrease in
current. The current measurement in the outer
chamber fluctuates according to the volume of smoke
particles.
Magnet and Reed Switch Test
The D281A Detector has a moisture-resistant reed
switch. Applying a magnet to the detector causes the
contacts in the reed switch to pull together, complete
the electrical circuit, and result in an alarm. The
magnet and reed switch test simulates a four to six
percent smoke concentration. The test is useful for
testing detectors located in environmentally unstable
or clean areas.
switch. Applying a magnet to the detector causes the
contacts in the reed switch to pull together, complete
the electrical circuit, and result in an alarm. The
magnet and reed switch test simulates a four to six
percent smoke concentration. The test is useful for
testing detectors located in environmentally unstable
or clean areas.
Indicators
The detector has two light emitting diodes (LEDs).
• Flashing green light: power is applied
• Steady red light: alarm signal
• Steady red light: alarm signal
Certifications and approvals
Region
Certification
USA
UL
UROX_S4992 - Smoke-Automatic Fire
Detectors
CSFM
7271-1615-0120
Hong Kong
HKFSD
HKFSD D281A D282A D283A D265AW
D282A-DH