Data Sheet for Product

Siemens
Smart Infrastructure – Building Products
–2–
usa.siemens.com/fire
Product Overview – (continued)
The encompassing result is an intelligent detector that provides enhanced detection capability to a wide range of
products of combustion
– while offering unsurpassed rejection to nuisance-alarm sources, including: dust | steam
| cooking aerosols and other deceptive phenomena that could cause false alarms. It is known at Siemens as the “No-false-
alarm guarantee”.
Since Model OOH941 is a two-wire, addressable device, functioning as a multi-purpose detector – satisfying the revised
requirements of UL 268 7
th
edition using smoke-and-heat detection in a singular, aesthetically pleasing package.
Comparable to other multi-functional detectors, Model OOH941 also serves as a very cost-effective, viable detection
solution that saves on product
| installation | maintenance costs. The unit’s value is multiplied with built-in
ISOtech nology the True Class-X - NFPA 72 compliant SLC isolation feature supporting up to 252 isolation ready devices
per loop. When used in mixed mode a maximum of 30 non-isolated devices between isolation devices (wired in polarity-
insensitive mode). Each detector fits into one (1) wall-or-ceiling footprint, and only occupies one (1) address on the
signal-line circuit (SLC).
A patented forward-and-backward, light-scattering technology, which is able to distinguish both small and large
products of combustion, operates at the core of each Model OOH941 intelligent, addressable detector. Each Model
OOH941 detector provides an eco-friendly solution to legacy ionization detectors - eliminating the need for a radioactive
source, along with inevitable HAZMAT-disposal requirements. Therefore, each detector is capable of detecting both
smoldering and flaming fire
─ all in ecologically efficient manner ─ and is a valid, RoHS-compliant (Restriction of
Hazardous Substances) detection alternative to legacy ionization detectors.
Two (2) thermal sensors make each Model OOH941 detector a robust, reliable device suitable for the most challenging
applications. Additionally, Model OOH941 works as a heat detector, compliant with NFPA 72 and UL 521.
Operation
Forward-and-Backward Light-Scattering Technology
The high-quality, optical-electronic measuring chamber for each Model OOH941 houses the following components:
 Two (2) optical transmitters
 Two (2) thermal sensors
 One (1) optical receiver
The transmitters illuminate the smoke particles from different angles: one sensor creates forward scatter, and the other
sensor creates backward scatter. The scattered light subsequently reaches the receiver (photodiode) and generates a
measurable electric signal. The combination of a forward-and-backward scatter facilitates optimum detection, as well
as differentiates between light-and-dark particles / particle size.
This type of detection creates standardized, responsive behavior, therefore optimizing the differentiation between
wanted signals and deceptive phenomena. Additionally, the heat sensors make it possible to detect fires without smoke
generation.
Additionally, this scenario generates the following advantages:
 Early detection of all fire types of fire ─ whether they generate light-or-dark smoke, or no smoke
 The fire detector can be operated at a lower sensitivity level, thus achieving a higher immunity against false alarms
that may otherwise be caused by cold aerosols (e.g
. ─ by smoking, electrical welding, etc.)
In the case of an open fire, the smoke sensitivity is heightened by a temperature increase
─ which means that a
detection-reliability level that is comparable to a wide-spectrum smoke detector ─ can be achieved and maintained.
Model OOH941
Forward-and-Backward Light-Scattering Technology
4. Forward
scatterer
5. Labyrinth
1. Heat
sensors
2.
Receiver
3.
Backward
scatterer