November 18, 1996
96-039
(External Distribution)
Recently, the fire service, building owners, designers and consultants have expressed concern about the audibility of fire alarm signals, particularly in residential buildings. This concern is due in part to the 2 Forest Laneway fire, but is also a result of the inclusion of a minimum 75 decibel (dB) sound level in the 1995 National Building Code (NBC). The issue of upgrading fire alarm audibility in existing buildings has come to the forefront through the enforcement efforts of the fire service and by Building Officials reviewing upgrades to fire alarm systems before issuing building permits.
The Ontario Fire Code (OFC) does not contain specific requirements under Retrofit that address the audibility of fire alarm signals. However, the OFM has indicated previously that if the audibility of an alarm system presents a hazard, it may be appropriate to issue a Fire Marshals Order (see Ontario Fire Code Opinions and Applications: 9.5.4.1. & 9.6.4.1. - Fire Alarm Systems).
Threshold sound level requirements are not referenced in either the OFC or the Ontario Building Code (OBC). Current regulations only stipulate that the alarm signals be heard intelligibly throughout the floor area (OBC 3.2.4.19.). The subjective nature of this requirement has created considerable debate and highlighted the need for consistency. The intent of the OBC requirement is that the alarm signal should be heard intelligibly by persons who are awake but need not be loud enough to wake persons who are asleep. This implies that a lower minimum sound pressure level (SPL) is required than the SPL in the 1995 NBC which is intended to wake people. To address this, the OFM is working to develop a guideline on the assessment of minimum sound levels for existing buildings.
As a consistent test to evaluate audibility is not available, some fire departments are establishing various SPLs as the criteria for accepting alarm systems in buildings that fall under both Retrofit (OFC) and new installations (OBC). These threshold levels, which vary from municipality to municipality, are based on the appendix of ULC’s Standard for the Installation of Fire Alarm Systems or the 1995 National Building Code. It is important that a consistent minimum SPL be used so that fire alarm systems which are replaced in existing buildings are approved under the same criteria as existing systems.
The audibility of alarm sound levels decrease significantly when passing through doors from the corridor to suite bedrooms. It is difficult to improve the audibility of an alarm signal by increasing the signal power in the corridors. Alarm sound levels at 110 dB in the corridors are ear shattering and make any voice communication in the corridor impossible. At this level, hearing damage can occur but an adequate signal may still not reach suite bedrooms. Adding an alarm signal in each suite may provide a solution to the audibility problem but it also raises other concerns.
In existing residential buildings, the cost of adding signalling devices in each suite is very expensive. It involves the installation of new electrical conduits for these new alarm signal circuits and may require the signal capability of the alarm system control panel and the size of the standby battery system to be increased.
Adding a different type of audible alarm device in apartment suites other than the alarm device used in the corridor may create some confusion for occupants. Its significance may be ignored and any subsequent fire safety education and training for occupants will become more difficult. Also, the new alarm signals added may reduce the reliability of the fire alarm system due to the potential for disconnection of the device and its vulnerability to fire damage. Locating alarm signalling devices in suites makes the system more susceptible to malicious damage, vandalism or tampering. When the alarm sounds, the devices in the suites may be too loud for occupants to ignore and as these devices are accessible, the unit may be disabled or disconnected. Since action at any location on the circuit may affect all other signals on the circuit, the entire circuit may not perform during an emergency.
A significant fire within an apartment suite will probably destroy the signal device and short circuit the connecting wiring. A short circuit at one location on the circuit will affect all of the signalling devices on that circuit. As a result, alarm signalling will either stop throughout the entire riser thereby affecting many floors or it will stop on the fire floor where occupants are closest to the fire.
Almost all fire alarm signal circuits are electrically supervised. The addition of any devices on an existing supervised circuit requires care during installation. Each device added should be tested to ensure that the electrical supervision of all devices on the circuit has not been compromised. Incorrect wiring on electrically supervised circuits cannot always be detected by just hearing that the signal operates.
The reuse of other existing wires, such as intercom system wiring for changes to the fire alarm system, is not an alternative. This contravenes the electrical code. An Ontario Hydro Inspector should be contacted prior to reusing any existing conduit for additions to the fire alarm system.
In-suite signalling devices form part of the fire alarm system and are subject to testing requirements under the Fire Code. Access to each unit, which is not always easy to obtain, is necessary to perform the testing required of the alarm system.
Questions related to fire alarm signal audibility are not easy to answer. Before embarking on a program to evaluate existing fire alarm systems based on sound level measurements, it is important to know how to make consistent measurements and to understand the issues related to modifying existing fire alarm systems.
The OFM has prepared information on the methods of measuring fire alarm system audibility to assist the fire service (see attached). The OFM is also developing a draft guideline to use when assessing the minimum SPL for fire alarm systems in existing residential occupancies. The OFM will be inviting comments from the fire service and other stakeholders prior to finalizing this guideline. In the interim, significant life safety concerns due to poor fire alarm audibility in an existing residential building may be addressed by issuing a Fire Marshals Order. Any requests for assistance should be directed to the OFM’s Research & Standards Section at (416) 325-3200.
|
||||||||||||||||||
