24 Apr 19
Public Safety Distributed Antenna Systems Cannot Sacrifice Survivability
A properly installed PSDAS guarantees that first responders have stable communications while a building is undergoing a fire or other emergency. This infrastructural system that provides emergency responders with two-way radio coverage is just as important as the building’s fire alarm, sprinkler, and security systems.
It is indisputable that Public Safety Distributed Antenna Systems (PSDAS) are considered to be critical building systems. As emergency responders cannot safely respond without communications,
Guaranteeing a life-safety grade power source has historically been the biggest failure of the public safety industry. Make no mistake, this industry has and continues to rapidly mature, but there are still many PSDAS installations without an incident-reliable power source. The trip cord scenario comes to mind - a firefighter’s red signal booster has been installed but the power source is a loose power cable to a standard, normal power wall outlet. This type of installation is unreliable and a trip hazard to any building maintenance! These requirements are in place because all PSDAS engineers, manufacturers, and installers should assume that the buildings' main power source has been lost. While many jurisdictions have imposed even more stringent standards, all active system components should meet the following requirements, including remote radio units in an active type of DAS:
- Source side power from a life-safety power riser, or a power source that is not at risk of intentional disconnection during an emergency.
- A life-safety breaker panel that is mechanically hardwired, or a secure panel that includes dedicated cutout(s) for the PSDAS installation.
- When the life-safety power riser does not include an automatic transfer switch to a backup generator, each system component must be supported with a local 12-hour battery backup.
Public Safety Distributed Antenna Systems are susceptible to accidental or malicious damage. Any damaged infrastructure prevents a PSDAS installation from working when an emergency occurs. For example, a single disconnected antenna inside a building can considerably hamper the operations of the PSDAS, not just in reduced coverage but through reflective, power harming overall system performance. While different municipalities have adopted different variations, there are established baseline requirements for mechanical integrity:
- All active system components installed away from the building’s fire command center should be housed in a NEMA 4 or 4X certified container that is locked with the local elevator recall key.
- All active system components should be monitored for access. Any uncontrolled access should trigger a trouble signal.
- The complete system should be monitored for connectivity so any damage can be identified.
- All system cables including coaxial, data, and power should be secured in EMT or conduit.
- All electrical junctions for power, RF, or data should be housed in a NEMA 1 electrical box.
- Red, Red, Red.
In the past, firefighter jacks and phones systems were expected to operate for two-hours to ensure communication and coordinated responses between firefighters. These systems have now been replaced by two-way radio communication enhancement systems, or TWRCEs. Unfortunately, it has been a consistent failing of the public safety DAS industry to provide fire-rated systems, to the point that many critics are saying it is not possible. However, an operational PSDAS during a fire is very possible with the following techniques:
- Select a system that supports fire-rated cabling.
- Automatically disconnect antennas that are exposed to a fire. The higher temperatures will prevent functional operation for the entire system.
- Install system components in existing fire-rated pathways or in slab raceways as the deck is being poured.
- Construct dedicated pathways protected by fire-rated construction.
- Include fire wrapping and conduit techniques.
Property managers and fire responders alike hope that these installations are never used but advanced engineering, products, and commissioning are not enough to ensure a building will have life safety communications when lives are on the line. After successfully commissioning a Public Safety Distributed Antenna System, the installation cannot be “set-and-forget,”. Similar to other life safety systems installed in the building, over time devices can become damaged or fail. These preventable issues can be solved by detecting and repairing system faults before the PSDAS is needed by first responders:
- Building inspections to check for certified coverage.
- Supervision of each antenna for connectivity, RF functionality, and Voltage Standing Wave Ratio (VSWR).
- Check for any system cable damage and if a ground fault is present.
- Replace batteries if they can no longer provide the required backup time.
- Guarantee that the signal booster is operating within factory parameters.
- Physically inspect the installation to make sure conduit, junction boxes, and electrical hookups are all fully functional.
- Ensure that the Dedicated Radio Monitor can audibly and visually enunciate the specific faults or supervisory signals.
- Check that the remote monitoring service and the fire alarm control panel is receiving signals.
Just like with any fire alarm or elevator recall, the Public Safety Distributed Antenna System is only useful when it is in a state of good repair. If a neglected antenna (or any other component) is able to prevent full system functionality during an emergency, that component needs to be supervised and replaced before the system fails first responders.
TowerIQ provides complimentary drawings for architects and engineers needing a life-safety wireless network. Just fill in our contact form below and one of our representatives will be in touch.
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