Understanding BDA Coverage & Frequency Requirements:
In Massachusetts, the requirements for emergency responder radio coverage in buildings are governed by §916 of the Massachusetts State Building Code (780 CMR). This section is fully amended such that it is unique to Massachusetts.
In accordance with 780 CMR §916.1, emergency responder radio coverage is to be provided throughout all new buildings. This often necessitates the installation of a Two-Way Radio Communications Enhancement System. Installing such a system may be avoided where a radio coverage survey test verifies that a minimum signal strength of -95dBm is achieved both into and out of the building in at least 95% of all areas. As radio signal strength is strongly impacted by building construction such as floor assemblies and wall assemblies, the need to install an enhancement system typically cannot be confirmed until late in construction.
Where a system is required to be installed, a Bi-Directional Amplifier (BDA) system is commonly implemented. This typically consist of a distributed antenna system (DAS) installed throughout each floor of the building and wired to amplifier equipment; the amplifier equipment then connects to an exterior donor antenna which communicates with the municipalities public safety communications systems.
Where a new BDA system is installed, general building areas must be provided with radio coverage in 90% of the floor area when tested in accordance with 780 CMR §916.5.3. Critical areas providing a means of egress or life safety equipment such as a fire pump room, Fire Command Center, or Fire Service Access Elevator Lobbies must have 99% floor area radio coverage per NFPA 72 (2013) §24.5.2.2.1. In all measured areas, inbound and outbound signal strength must be a minimum of -95dBm. Again, radio coverage is greatly impacted by building construction such as floor assemblies and wall assemblies and should be taken into consideration when a radio signal survey is conducted.
Two-Way Radio Communications Enhancement Systems generally need to accommodate several different radio frequencies in order to address the responding fire department’s needs (dispatch channel, fireground/tactical channels, mutual aid channels, etc.) as well as any frequencies required by other emergency responders that require radio coverage. Ultimately, the fire code official is charged with maintaining the list of frequencies currently required to be supported. However, if at any point in the future municipal frequencies are changed or added by the FCC or an AHJ, the system is expected to be modified or expanded to accommodate these changes at ownership’s expense per NFPA 72 §24.5.2.4.2 & 780 CMR §916.6.2.
Final confirmation of the need to install a BDA system often comes late in construction, at a point where installation of associated equipment, wiring and antennas can be disruptive and costly. Further, where a system is provided, the system is expected to be able to accommodate future expansion to cover new or changing frequencies. The associated cost impacts may come in the form of additional equipment, labor and schedule delays. All of these risks should be taken into consideration during BDA system design.