Emergency Responder Radio Coverage for New and Existing Buildings

Issue 11 and Volume 13.

Emergency first responders use portable radios (known as land mobile radios, or LMRs) as a critical communication tool to ensure effective fireground command and control, for personnel accountability, and to improve firefighter safety when operating within buildings during a fire or other emergency. Fire departments equip their interior firefighters with LMRs as an essential tool necessary for firefighters to operate in the hazardous conditions caused by fire. These tools are essential for communication with the incident commander, dispatch center, and other firefighters while carrying out firefighting and rescue duties. Portable LMRs can also be a firefighter’s lifeline when a calling a Mayday, but the user needs the assurance that the message is both sent and received so that immediate rescue of a trapped or injured firefighter can be initiated.

Given the importance of portable LMRs to firefighter safety, it is essential for these LMRs–which operate on the public safety frequency used by the municipality—to operate reliably anywhere within a building at all times. The necessary signal strength is typically available in residential dwelling units but may require an enhancement system in larger commercial use buildings and in high-rise or underground buildings. In these locations, construction features may inhibit or block normal LMR transmission or receiving functions.

In-building emergency radio communication enhancement systems for two-way portable LMRs have been commercially available for many years. There are several different types of systems with varying features and costs that provide a range of design and installation options.

Current Technologies

Here is a brief overview of the technologies available today.

Radiating cable system (AKA leaky cable). A radiating cable is a long, flexible antenna with slots that broadcast radio frequency (RF) signals; hence, its descriptive name of leaky cable. A radiating cable is a passive system that does not amplify the RF signal, and this system normally experiences a loss of signal strength over distance. The reliability of these systems is also affected by other proximal RF signal interference.

Radiating cable systems can be installed in new or existing buildings to enhance emergency two-way radio capability. Since this cable comes in multiple lengths and is flexible, this antenna system can be installed in mechanical shafts, stairways, or corridors within a building to provide RF coverage throughout the facility.

Distributed antenna system. A distributed antenna system (DAS) is a system of managed hubs and remote antennas that distributes an RF signal to a portable radio within a building. These systems may employ passive and/or active components. At the head-end of the DAS, a base station or repeater provides the signal. A main hub takes that signal, digitizes it, and distributes it to other hubs and radios via a high-bandwidth fiber optic network. At each remote hub, the device converts the signals from digital to RF and from RF to digital and distributes the RF signal over the distributed antenna covering a portion of a building. By digitizing the signal on the fiber optic network, the DAS can transport the mobile signal at full strength to any remote antenna connected, no matter how far away it is from the main hub and base station.

DAS is used in new or existing buildings with a need to enhance the emergency two-way LMR capability. By focusing a base station’s signal on a specific area through remote antennas, the DAS delivers higher capacity and consistent coverage over the area it serves.

Amplification (booster) systems and bi-directional amplifiers (BDAs) are also components of a DAS.

Relevant Codes

Requirements for in-building emergency radio communication enhancement systems were first introduced into the International Fire Code (IFC) in the 2009 edition as Section 510 (Emergency Responder Radio Coverage). These initial model code requirements were very basic and simply required all newly constructed buildings to have approved radio coverage for emergency responders available throughout the interior of the building at the same coverage levels that existed outside of the building. The intent at the time was not to mandate better public safety radio system coverage or signal strength within a building when compared with the signal strength available outside, nor was the intent to impose a mandate that the existing public safety communication system be upgraded or improved.

The IFC also added a requirement for existing buildings that did not already have an approved emergency radio or communication system to meet the same requirement in effect for new buildings within a timeframe established by the authority that adopts the fire code. Technical requirements were added in a new adoptable appendix (Appendix J) of the IFC for those jurisdictions that wished to mandate technical requirements.

In 2012, the technical requirements of Appendix J were relocated into Section 510 as mandated provisions. The 2102 edition also added a new Chapter to the IFC: Chapter 11, “Construction Requirements for Existing Buildings.” The requirements for in-building emergency radio communication enhancement systems in existing buildings were added to this Chapter in Section 1103.2, clarifying the intent that this was to be mandated, retroactive requirements unless the fire official waived the requirement based on a determination that the enhanced communication system was not needed.

There have been further modifications to IFC Section 510 in both the 2015 and 2018 editions to address technical issues that arose as more systems were being installed in both new and existing buildings. Other changes were made to embrace new technology and better clarify the intent and understanding of the code for the design, installation, testing, and commissioning of these systems. Additionally, the inspection and maintenance requirements necessary to ensure system reliability were also incorporated in the 2018 IFC.

The NFPA 1 model Fire Code also added very similar requirements covering in-building emergency radio communication enhancement systems in the 2012 edition, Section 11.10 (Two-Way Radio Communication Enhancement Systems). In the 2012 edition of NFPA 1, the requirements were also basic and included a reference to comply with requirements found in NFPA 72. The requirements for these systems were relocated from NFPA 72 and placed in the 2016 edition of NFPA 1221, Standard for the Installation, Maintenance and Use of Emergency Services Communications Systems. The 2018 edition of the IFC added a requirement for these systems to be designed and installed in accordance with NFPA 1221.

The 2016 edition of NFPA 1221 includes Section 9.6 (Two-Way Radio Communication Enhancement Systems) with technical requirements for design, installation, and performance generally consistent with the 2018 IFC Section 510.

Other jurisdictions, such as New York City, have their own local code requirements for these systems. As of December 31, 2014, Sections 403.4.4 and 907.2.13.2 of the New York City Building Code (NYCBC) require that an in-building auxiliary radio communication (ARC) system be installed and maintained in all newly constructed high-rise buildings. NYCBC Section 917.1.2 and Section 511 of the NYC Fire Code together require that ARC systems be installed, acceptance tested, operated, and maintained in accordance with the Fire Code and the rules of the fire department.

The technical requirements for design, installation, commissioning, inspection, testing, and maintenance of in-building emergency radio communication enhancement systems included in the IFC, NFPA 1, and NFPA 1221 are summarized as follows:

  • Typical system operation is continuous or automatic.
  • The IFC requires specified signal strength into and out of the building with a Delivered Audio Quality (DAQ) of 3.0 in 95 percent in all areas; NFPA 1 and 1221 require 90 percent coverage in general building areas and 99 percent in critical areas such as fire command centers, elevator lobbies, exits, and fire equipment rooms. Efforts are underway to harmonize the difference between these two codes in the next code development cycle. Note: DAQ is simply a qualitative measurement of voice intelligibility or clarity.
  • The equipment must be approved. The system design and operation must be specifically designated for use as an in-building emergency radio communication enhancement system by the manufacturer.
  • The system must meet specific survivability requirements to ensure it will continue to operate during a fire.
  • The system must have redundant primary power sources and stand-by or backup power to operate at 100% capacity for at least 12 hours.
  • The system must be monitored through the building’s fire alarm system for loss of power; failure of the battery charger; low-battery capacity indication when 70% of the 12-hour operating capacity has been depleted; malfunction of the donor antenna and active RF-emitting device(s); and failure of any critical system components and provide either an audible warning or “trouble” signal.
  • The system performance and reliability must be tested on installation and maintained operational at all times.  An annual inspection is also required.

Additional safety and performance testing and certification for these systems and components is on the horizon. At the request of the fire service and industry, UL recently published UL 2524, In-building 2-Way Emergency Radio Communication Enhancement Systems (https://standardscatalog.ul.com/standards/en/outline_2524_1). This new standard addresses the following requirements for discrete equipment used for in-building two-way radio communication enhancement systems installed in a location to improve wireless communication at that location:

  • Safety (risk of fire and risk of shock) requirements–construction and testing
  • Compliance with specific performance requirements in accordance with the IFC 2018 and NFPA 1221-2016

Further additions are planned for the next edition to address reliability requirements applicable for life safety systems. These requirements will be modeled after those used in other life safety systems, such as UL 864, Fire Alarm Control Units and Accessories. 

UL 2524  has completed the  ANSI consensus standard process with review and balloting by a Standards Technical Panel (STP) that was completed in early October 2018. STPs are an important part of the process by which UL develops and maintains its Standards for Safety. An STP is a group of individuals, representing a variety of interests, formed to review and act on proposals related to UL standards.

UL’s Collaborative Standards Development System (CSDS) provides online access to review and submit proposals for UL’s standards development process. General access is available for information on STP meetings, submitting proposals, and access to free proposals. More information about CSDS is available on the UL Web site (https://ulstandards.ul.com/develop-standards/).

Properly designed, installed, and maintained in-building emergency radio communication enhancement systems provide a cost-effective and reliable tool for firefighter communications during fire or other emergencies within our built environment. In a world where we depend on constant access to digital and verbally transmitted data and information, ensuring that all buildings are equipped with a reliable emergency radio communication enhancement system is critical for both emergency responder and occupant safety. Effective development and administration of the model code requirements and third-party, independent testing and certification of these systems can help ensure vital emergency communication capability will be in place and operational whenever a building fire or other emergency occurs.


Bruce Johnson is a senior regulatory engineer in UL’s Codes and Advisory Services Department, joining UL in April 2015. Prior to joining UL, he served several decades in the fire, emergency services, and life safety arena beginning his career in the late 1970s as a firefighter on Long Island, NY. Most recently, he worked for the International Code Council (ICC) as a vice president in the Government Relations Department. He serves on several ICC code committees and is an alternate on NFPA Technical Committees for NFPA 1, 101, 730. 731, and 5000.

He is also an Adjunct College Instructor at SUNY Empire State College. He earned a bachelor degree in fire service administration from Empire State College, a bachelor’s degree in accounting from Dowling College, and a master’s degree in business administration from the University of Southern California.

Larry Shudak is UL’s principal engineer for life safety technologies including fire alarm control, mass notification, and emergency signaling systems. He is UL’s technical expert on various UL and ULC standard technical panels/committees and is a member on several NFPA technical committees, including NFPA 72, 101, 92, and 3 and 4. He authored the first edition of UL 2524, In-building 2-Way Emergency Radio Communication Enhancement Systems.