Shooter Detection Systems (SDS) - Sensor placement guide
To get the best placement of the Shooter Detection Systems (SDS) Powered by Alarm.com sensors, it is important to acquire floor plan documents from the customer. These documents should be tailored to the correct amount of detail so the security (dispatch) team understands the sensors' location during a triggered event. Too much or too little information will reduce the effectiveness of the system and the information it provides the first responders.
In many cases, an initial design and estimate can be accomplished using only the floor plan documents, and then performing an on-site walk is required to verify the sensor placements are correct and not obscured by items not shown on the floor plans.
Coverage area and placement
Coverage pattern
The coverage pattern, as defined by Alarm.com, is the minimum distance at which the sensor will detect a low-caliber firearm facing away from the sensor and fully occluded (blocked) by the body of the shooter. This is what defines the pattern and minimum distance as the basis for placing sensors within a facility. Depending on caliber and other factors, the detection range may be further.
The coverage pattern for the sensor is represented by a half circle with a coverage arc that stretches 40 feet and covers 180 degrees. This offers a minimum approximate coverage of 2,500 square feet. The radius of the coverage arc is 40 feet with a diameter of 80 feet.
The 2D coverage pattern extends upward from the floor to the height at which the sensor is mounted. For simplicity, a sensor placement drawing may be constructed using only the 2D shape.
Ranging
The use of both IR and Acoustic signatures allows for an additional feature of the system, ranging. The range (distance) of the firearm from the detector can be calculated using the time of arrival of the two independent signals.
This allows added detection capabilities within the sensor as well as the ability to exclude shots that fall outside the maximum range. This can be useful in open areas (e.g., airports) where many sensors are collocated. By excluding shots that are beyond a particular range (80 ft), this avoids many sensors alerting over a wide area and focuses strictly on the area where shots have been fired.
The sensor does not use triangulation and each sensor operates independently allowing for simple placement and deployment of the sensors.
Wall and ceiling mounting
The sensor may be placed on either a wall or ceiling. The geometry of the front end of the sensor has been designed in such a way that the coverage pattern is identical in either placement.
In other words, the pattern (semi-circle) and coverage distance are identical regardless of wall or ceiling mounting configuration.
Sensor direction and orientation
The sensors offer a 180-degree field of view and must be placed in the proper direction and orientation.
When mounting the sensor on the wall, the infrared detectors must face downward and the acoustic sensors must be on top as shown in the following image.
When mounting the sensor on the ceiling, the acoustic sensors must face toward the wall or area away from coverage and the Infrared detectors must face toward the area of coverage as shown in the following image.
Field of view
Though the sensor requires acoustics and Infrared signals, it is not a line-of-sight system. This means that it does not require a direct view of the firearm to detect a gunshot event. When following the guidelines and coverage pattern outlined in the preceding sections, the sensor will detect a gunshot without direct sight of the event (e.g., a gunshot that is blocked (fully occluded) by the shooter's body from the sensor).
The sensors cannot however hear or see-through walls or other large obstacles. An example of a large obstacle may be a sizable column placed near the sensor or an overhang or horizontal beam directly blocking the view of the sensor.
When placing sensors, the units should be placed with a clear view of the coverage area.
Best practice placement
|
T intersection of a hallway
|
An example of a good coverage design would be to place the sensor at a T intersection of a hallway. Additionally, sensors should not be placed in corners. This significantly blocks the 180-degree coverage pattern of the device. A better placement is midway along the wall of a hall or room to allow a wide view of the area to be covered. |
|---|---|
|
Long corridor
|
The sensor coverage pattern is an arc and therefore thoughtful placement may be required in some instances. For instance, when placing sensors down a long corridor the sensors can be placed 80 feet from each other. As a best practice, though not required, sensors would be placed on opposite walls so that the curvature of the coverage area aligns. |
|
Large open spaces
|
Placing sensors in a large open space allows good use of the available coverage area, however, mounting locations may be more difficult to find. If ceiling mount is an option and ceiling height is not prohibitive, this could be a good option. Alternatively, sensor spacing may be decreased to offer a longer width of coverage, while limiting the coverage gap between sensors as shown in the following image. This is only necessary when mounting locations are not available. |
Sensor height considerations
Height requirements
The sensor must be mounted within the proper height range to maintain the minimum coverage area. The following guidelines are shown for a wall mount application, though the exact same height requirements apply for ceiling mount as well.
The heights noted in this section are from the finished floor. The preferred mounting height range is 9 to 12 feet. The sensor may be mounted as high as 16 feet with no performance or coverage impact.
A sensor should only be mounted between 8 and 9 feet if the ceiling height is restricted.
Important: Never mount a sensor higher than 16 feet or lower than 8 feet. A sensor should never be placed at a height or location where it may be easily touched.
Clearance
The sensor must be placed a minimum of 2 inches from the wall or ceiling edge. This is primarily to allow access for the handheld tester to be placed over the sensor during verification testing. Placement near other objects should also be avoided for the same reason.
Environment considerations
The following precautions must be followed to maintain the specified false alert rate.
Infrared lighting sources
Sensors should not be placed near lighting sources that produce a large amount of Infrared (e.g., a traditional incandescent light bulb) or other high-energy lighting sources (e.g., those in a gymnasium). While this may be difficult to determine, generally lighting sources that produce a large amount of heat will produce Infrared in the specific band of concern.
Where possible the sensor should be placed out of direct view of these lighting sources. The required distance from the source will depend on the intensity of that source. A general guideline would be that: if the source falls into the category outlined above and there is a strong shadow cast when blocking the lighting source, this area can be a concern. The sensor will report a warning of High IR Source if placed in this location.
Infrared remotes, motion sensors, and similar devices are in a different band of the Infrared spectrum and do not cause concern for the proper operation of the sensor. LED and fluorescent lighting do not produce Infrared in the spectrum of concern and are also not an issue.
Fire alarms, sirens, bells, and strobes
A sensor should be placed a minimum of 1 foot from standard fire alarm sirens and strobes.
A sensor should be placed a minimum of 4 feet from alarms or bells which are considerably louder than a standard fire alarm system.
Welding equipment
A sensor should never be placed in an area with welding equipment of any kind (e.g., gas, arc, spot, etc.) The welding process can create both loud and impulsive sounds which are directly associated with Infrared pulses. Sensors must be placed a minimum of 100 feet from welding sources, including temporary construction equipment.
Construction zone
As mentioned above, sensors should not be placed in a construction area. Beyond welding equipment, it is recommended that sensors are disabled in software during any large construction projects. While the gunshot sensor performs well against nail guns (powder and pneumatic), as well as other construction equipment, it is recommended that sensors within 100 feet of the construction are disabled to limit risk.
Direct impact
A sensor placed in an area where it is likely to be hit by an object (e.g., in a gymnasium) should be placed in a protective cage.
An example of a protective cage is American Time's G2084, which provides a good fit for the sensor. For more information, refer to American Time's Thermostat Guard G2084.
Safety Technology International (STI) also provides protective cages. For more information, refer to STI's Clock/Bell Damage Stoppers.
Other cages can be used to protect the sensor. The chosen cage must not utilize large structures which could prevent the sensor's view of the shooter.