Xtralis OSID, or Open-area Smoke Imaging Detection, is an imaging-based projected-beam smoke detection system designed for large open spaces such as stadiums, warehouses, atriums, arenas, gymnasiums and other difficult smoke-detection environments.
Instead of relying on a conventional beam detector and reflector arrangement, OSID uses an imager and one or more emitters. The system analyzes dual-wavelength ultraviolet (UV) and infrared (IR) light to distinguish smoke from many environmental and obstruction conditions.
I originally wrote this article after installing OSID in one of the more challenging real-world environments I could have asked for: the Oakland Coliseum sports complex.
Why I Originally Wrote About OSID
When I first started working with Xtralis OSID, we had about as difficult a real-world environment as you could ask for to evaluate beam-type smoke detection: the Oakland Coliseum.
At the time, the Oakland Coliseum was home to the Oakland Raiders, while the Golden State Warriors played next door at the arena within the Coliseum sports complex.
This was not a quiet warehouse where a beam detector could spend its life looking across an empty ceiling.
It was a major sports and entertainment environment with thousands of fans, vibration and structural movement, changing atmospheric conditions, smoke and haze, airflow, and all the activity associated with packed sporting events.
People jumping and cheering might sound completely unrelated to fire alarm detection until you remember that traditional projected-beam detectors can be affected by movement and alignment. When detection equipment is installed high above a floor, every unnecessary alignment or service trip can become a major event.
That is where OSID got my attention.
In my field experience, the OSID system performed extremely well in this demanding environment. The imaging technology and its tolerance for movement and environmental conditions made a strong impression on me, especially after years of dealing with conventional beam-detector alignment.
The photographs throughout this article are not manufacturer promotional photographs or stock images.
They are photographs from our actual OSID installation work.
That real-world experience is one of the main reasons I originally wrote this article and why I wanted to preserve these photographs in this updated technical guide.
Interestingly, the characteristics that impressed me in the field remain central to how Xtralis describes OSID today, including tolerance to building movement, vibration and challenging environmental conditions.
What Is a Beam Smoke Detector?
A projected-beam smoke detector is a fire alarm detection device that monitors smoke across a large open space using a projected optical path.
Instead of installing numerous spot-type smoke detectors throughout a large ceiling area, a properly designed beam detection system can monitor a much larger area along its beam path.
Beam smoke detection is commonly considered for applications such as:
- Warehouses
- Atriums
- Gymnasiums
- Arenas and stadiums
- Aircraft hangars
- Large manufacturing areas
- Transportation facilities
- Entertainment venues
- Other large or high-ceiling spaces
The actual detector spacing, beam location, mounting height and application must be designed in accordance with the adopted fire alarm code, the detector's listing and the manufacturer's published instructions.
Why Can Traditional Beam Detectors Be Difficult?
Whether you have been in the fire alarm industry for a month or several decades, there is a good chance you have heard technicians express a love-hate relationship with beam detectors.
The concept is excellent. Protect a large open area without installing dozens of individual detectors, miles of additional wire and conduit, and numerous devices in locations that may be extremely difficult to access.
The challenge has traditionally been installation, alignment and maintaining that alignment.
Early beam systems I worked with used separate transmitter and receiver assemblies. Later reflected-beam designs eliminated the separate receiver by sending the beam toward a reflector and measuring the light returned to the detector.
Those developments simplified wiring, but precise alignment could still require patience.
Then there is the building itself.
Large structures move. Steel expands and contracts. Roof systems react to temperature. Equipment vibrates. Crowds and building activity can introduce movement. Even a relatively small change at the mounting point can matter over a long optical path.
And unfortunately, beam detectors are rarely mounted six feet above the floor where you can casually adjust one from a stepladder.
That was the problem that made OSID so interesting to me.
What Is Xtralis OSID?
OSID stands for Open-area Smoke Imaging Detection.
Xtralis is well known in the fire alarm industry for VESDA aspirating smoke detection, but OSID takes a different approach to protecting large open areas.
The system uses two primary components:
- Imager - the receiving and processing portion of the system.
- Emitter - the optical source monitored by the imager.
In simplified terms, think of the imager as watching for and analyzing the light coming from one or more emitters within its field of view.
That is different from a traditional reflected-beam arrangement where precise alignment is required to send an optical beam toward a reflector and return it to the detector.
How Does OSID Detect Smoke?
One of the most important parts of OSID technology is its use of two wavelengths of light: ultraviolet (UV) and infrared (IR).
Smoke affects those wavelengths differently.
By analyzing the relative attenuation of the UV and IR signals, OSID can determine whether the optical path is behaving in a manner consistent with smoke rather than simply treating every reduction in received light as a fire condition.
This imaging and dual-wavelength approach is a major reason the technology can tolerate many conditions that can challenge conventional optical beam systems.
Environmental tolerance does not mean that OSID can be installed anywhere without engineering consideration.
Detector selection, sensitivity, distance, field of view, beam location, mounting surfaces, airflow, ceiling geometry and environmental conditions must still comply with the current manufacturer's listing and installation instructions and the adopted fire alarm code.
OSID at the Oakland Coliseum: Why the Application Mattered
The Coliseum installation is important to this story because it demonstrates why imaging-based beam detection caught my attention in the first place.
Think about the environment inside and around a major sports venue:
- Large open spaces
- Long detection distances
- Difficult device access
- Structural movement and vibration
- Large crowds
- Thousands of people jumping and moving during events
- Air movement
- Smoke, haze and changing atmospheric conditions
- Equipment mounted where repeated service access is expensive and inconvenient
Those are exactly the kinds of conditions that make reliable detection and stable alignment important.
In our installation, OSID proved to be remarkably stable. That experience was not a laboratory test and should not be interpreted as a universal performance guarantee. It was my real-world field experience with the technology in a demanding venue.
Years later, that installation remains one of the reasons I remember OSID so clearly.
What Makes Up an OSID Beam Detection System?
The original OSID system documented in these photographs used the OSI-10 and OSI-90 imager family along with compatible OSE emitters.
Those product families remain supported by Xtralis, but specifications and listings have evolved since this article was first written. Always use the current product documentation for a new design.
OSID Imager
Two of the best-known imagers in the OSID-DE family are the OSI-10 and OSI-90.
OSI-10
The OSI-10 uses a narrow-angle lens and monitors a single emitter.
Current Xtralis documentation identifies a 10-degree lens with an approximately 7-degree usable horizontal field of view. This distinction is worth noting because older literature, including the original version of this article, described the field of view differently.
For U.S. UL installations, the allowable detection range depends on the listed sensitivity and emitter configuration. Do not use an old blanket distance from a legacy article when designing a current installation.
OSI-90
The OSI-90 provides a much wider field of view and can monitor up to seven emitters.
Current manufacturer literature identifies approximately 80 degrees of usable horizontal field of view.
This allows one imager to monitor multiple emitters located at different positions within a large space, making the OSI-90 particularly interesting for applications such as atriums and other geometrically complex open areas.
OSID Emitters
OSID emitters have been offered in standard-power and high-power configurations, with wired and battery-powered options depending on the product and listing.
The emitter configuration matters because it can affect allowable detection distance, installation requirements and compatibility with the selected imager.
Xtralis publishes specific UL configuration tables for OSID-DE.
Those tables establish the allowable detection ranges for the selected imager, emitter type and sensitivity. Because those specifications can change with listings and product revisions, use the current Xtralis UL product guide and installation sheet rather than treating the numbers in an older field article as design criteria.
Single-Emitter vs. Multi-Emitter OSID Applications
One of the features that separates the OSI-90 from a traditional one-to-one beam arrangement is the ability to monitor multiple emitters from a single imager.
For a straightforward one-to-one application, a narrow-field imager and single emitter may be appropriate.
For a large atrium or another space where several optical paths are required, an OSI-90 can monitor multiple compatible emitters within its field of view.
This does not mean that simply adding emitters automatically provides a particular square-foot coverage.
The original version of this article included generalized square-foot figures. I have intentionally removed those from this updated version because projected-beam smoke detection must be designed around actual beam spacing, ceiling geometry, mounting location, airflow, listed equipment limitations and the adopted code.
OSID Installation and Mounting
One of the things I liked when first installing OSID was the mechanical design.
The imager and emitter assemblies use mounting hardware designed to make positioning and alignment practical even when the units are installed on different surfaces or at different angles.
Inside the OSID Imager
The imager provides the electrical connections and configuration required for alarm, fault, power and related system functions.
Configuration details, terminal functions and switch settings can vary by hardware and firmware revision. For that reason, the current Xtralis installation sheet should be followed rather than using an old switch-setting description from this article as a commissioning instruction.
OSID Mounting Bracket
The mounting surface is important.
Even though OSID is designed to tolerate movement better than many conventional beam arrangements, the equipment still needs to be installed on a suitable, structurally sound surface in accordance with the manufacturer's instructions.
How to Align an OSID Beam Smoke Detector
This was one of the features that impressed me most during the original installation.
Traditional beam alignment can sometimes feel like trying to thread a needle from the opposite end of a warehouse.
OSID uses an adjustable optical assembly and alignment tools to simplify the process.
The original installation shown here used the OSP-002 laser alignment tool.
Align the Emitters First
On the system documented in this original installation, we began with the emitter side.
The adjustable ball-and-socket arrangement allowed the emitter optics to be aimed toward the imager. The laser alignment tool provided a visible reference for getting the optical assembly into the required alignment zone.
Then Align and Train the Imager
After the applicable emitters are positioned, the imager is aimed so that the required emitters fall within its usable field of view.
The imager then goes through its commissioning or training process so the system can identify the configured emitters and establish its operating reference.
The exact commissioning sequence, LED indications, timing and software procedures should be taken from the current Xtralis installation and commissioning documentation because those details can change with firmware and product revisions.
Alignment is not merely an installation issue.
If a detector is mounted 30, 40 or 60 feet above the floor, every unnecessary return trip can require lifts, building access, shutdown coordination and significant labor.
A detection system that remains stable after commissioning can therefore provide a very practical service advantage.
OSID and Building Movement
This deserves its own section because it was one of the biggest reasons I became interested in OSID.
Large buildings are not perfectly rigid.
Temperature changes, structural loading, wind, vibration and normal building activity can produce movement.
With a tightly aligned traditional optical arrangement, movement at one end of a long beam path can affect alignment.
OSID's imaging approach provides a field of view in which the imager identifies the emitter rather than depending solely on an optical beam returning to one extremely precise point.
That does not make mounting requirements irrelevant, but it provides a fundamentally different approach to dealing with alignment and movement.
That difference became very real to me in the Coliseum environment.
What About Fog, Haze, Dust and Other Environmental Conditions?
This is another area where the dual-wavelength design matters.
OSID evaluates both UV and IR attenuation rather than making a decision based only on a single optical measurement.
Current manufacturer literature describes the system as designed for high immunity to many nuisance conditions and environmental interference.
That is particularly attractive in large venues, industrial environments and other applications where dust, haze, steam, reflections, temporary obstructions or environmental changes may be present.
Again, this is not permission to ignore the environment during design. The expected conditions still need to fall within the equipment's listed operating parameters.
Where Does OSID Make Sense?
OSID deserves consideration where projected-beam smoke detection is appropriate and the application benefits from imaging-based detection.
Examples can include:
- Large warehouses
- Stadiums and arenas
- Atriums
- Gymnasiums
- Entertainment venues
- Large manufacturing spaces
- Transportation facilities
- High-ceiling open areas
- Applications where conventional beam alignment or movement is a concern
- Retrofits where the system configuration supports an OSID solution
When Might OSID Not Be the Best Detection Method?
No smoke-detection technology is automatically the best solution for every building.
Depending on the hazard, ceiling configuration, airflow, required response, access and project objectives, the designer might instead consider:
- Spot-type smoke detection
- Conventional projected-beam smoke detection
- Aspirating smoke detection such as VESDA
- Air-sampling detection
- Other listed detection technologies appropriate to the hazard
The correct question is not simply, "Which detector is coolest?"
The real question is:
NFPA 72 Requirements for Projected-Beam Smoke Detection
OSID is still fire alarm smoke detection equipment and must be designed and installed within the applicable code and listing framework.
NFPA 72 addresses projected-beam smoke detectors as part of the smoke-detection requirements in Chapter 17.
A key principle is that projected-beam smoke detector spacing and placement must follow the manufacturer's published instructions.
NFPA guidance also treats each projected beam as comparable to a row of spot-type smoke detectors for spacing purposes.
The designer must also consider factors such as:
- Ceiling geometry
- Ceiling height
- Beam spacing
- Distance from sidewalls
- Airflow
- Smoke stratification
- Structural obstructions
- Accessibility for inspection, testing and maintenance
- The detector manufacturer's listing and installation instructions
Do not use a generic square-foot coverage number to lay out projected-beam smoke detectors.
Beam placement is a design exercise involving the adopted NFPA 72 edition, ceiling configuration, environmental conditions and the specific detector manufacturer's listed installation requirements.
Inspection, Testing and Maintenance
High-ceiling detection still has to be inspected, tested and maintained.
That consideration should begin during design, not after someone discovers that a detector can only be reached with a specialized lift.
OSID provides alarm and fault supervision along with diagnostic capabilities that can assist technicians with commissioning and troubleshooting.
Xtralis continues to provide OSID commissioning documentation and diagnostic software for the OSI-10/OSI-90 family.
Always use the current maintenance and test procedure applicable to the installed model, firmware and listing.
What I Think About OSID After Real-World Installation Experience
When I originally wrote this article in 2017, OSID was still relatively new technology to many technicians I worked with.
My enthusiasm came from actually installing it and watching it perform in an environment where I expected beam detection to be challenging.
The Oakland Coliseum sports complex gave us vibration, movement, crowds, difficult access and changing environmental conditions.
The system impressed me.
That does not mean OSID is automatically the correct detector for every large space.
It means that when imaging-based projected-beam detection fits the design criteria, OSID offers a very interesting alternative to traditional beam arrangements, particularly where alignment stability and environmental tolerance matter.
And years after I originally wrote about it, the OSI-10/OSI-90 product family remains supported by Xtralis.
OSID Beam Detector Frequently Asked Questions
What does OSID stand for?
OSID stands for Open-area Smoke Imaging Detection. It is an imaging-based projected-beam smoke detection technology developed by Xtralis.
How does an OSID beam detector work?
An OSID imager monitors light produced by one or more emitters and analyzes ultraviolet and infrared wavelengths. Changes in those optical signals allow the system to detect conditions consistent with smoke while providing resistance to many nuisance conditions.
What is the difference between OSI-10 and OSI-90?
The OSI-10 is a narrow-field imager intended for a single emitter. The OSI-90 provides a much wider field of view and can monitor multiple compatible emitters. Exact ranges and configurations depend on the current listing, sensitivity and emitter selection.
How many emitters can an OSI-90 monitor?
The OSI-90 can monitor up to seven compatible emitters when configured in accordance with the manufacturer's requirements.
Can OSID be used in a stadium?
Stadiums and other large open venues are among the types of applications identified for OSID. The system still must be engineered for the specific building, environment, beam layout and adopted code requirements.
Does OSID tolerate building movement?
OSID's imaging approach and field of view are designed to provide greater tolerance to movement and alignment variation than a narrowly aligned conventional beam arrangement. The equipment must still be mounted according to the manufacturer's requirements.
Can fog or haze cause problems with beam smoke detectors?
Atmospheric conditions can affect optical smoke detection. OSID uses dual UV and IR wavelengths and imaging algorithms specifically intended to help distinguish smoke from many nuisance and environmental conditions. The expected environment must remain within the product's listed operating limitations.
Does OSID replace every conventional beam detector?
No. OSID is one detection option. Conventional projected-beam detection, spot detection and aspirating smoke detection can all be appropriate depending on the building and fire protection objectives.
Does NFPA 72 allow OSID beam smoke detectors?
Projected-beam smoke detection is addressed by NFPA 72. The detector must be listed for its application and installed according to the adopted code and manufacturer's published instructions.
Current Xtralis OSID Technical Information
Because product listings, firmware and installation requirements can change, use the current manufacturer's documentation when designing, installing, commissioning or servicing OSID equipment.
The official Xtralis OSID technical library contains current product guides, UL installation sheets, commissioning information, technical bulletins and diagnostic software.
View the Official Xtralis OSID Technical Documentation
The Bottom Line
I had spent years dealing with the compromises of traditional beam detection when I first encountered OSID.
Then I had the opportunity to install it in a place that could really put the concept to work: the Oakland Coliseum sports complex.
Huge spaces. Difficult access. Vibration. Movement. Crowds. Changing atmospheric conditions. Thousands of people making a building feel very much alive.
And the OSID system performed extremely well in my field experience.
That is why I originally wrote this article.
The technology should still be selected and designed like any other life-safety detection system: based on the hazard, building, adopted NFPA 72 requirements, listing and manufacturer's instructions.
But when imaging-based beam detection fits the application, OSID provides an approach to open-area smoke detection that is very different from the traditional beam detectors many technicians grew up fighting with.
Technical Disclaimer: Fire alarm systems are life-safety systems. Detector selection, spacing, installation, commissioning, testing and maintenance should be performed by qualified personnel in accordance with the locally adopted codes, approved design documents, equipment listing and manufacturer's published instructions. Product specifications can change. Always verify current Xtralis documentation for the exact equipment being installed.
