Current Trends in Automatic Fire Alarm Systems Explained

Introduction

Every year, thousands of people die in home and commercial building fires, but far more are saved as a result of fire alarm systems that provide sufficient notice to evacuate the premises. In the distant past, fire alarm systems consisted of men and sometimes animals, but more recently, increasingly sophisticated systems have been developed that form an essential part of the concentric layers of building defense. To identify current trends in this field, this paper provides a review of the relevant peer-reviewed and scholarly literature concerning automatic fire alarm systems in general, as well as their composition and working principles in particular, including their design, basic configuration, and the types of notification devices that are typically used. The paper also examines detectors, emergency voice systems, and other alarm communication systems currently deployed, with respect to the Americans with Disabilities Act Accessibility Guidelines for fire alarm systems. Finally, a summary of the research and important findings is presented in the conclusion.

How Automatic Fire Alarm Systems Operate

Fire alarm systems form an important part of what has been conceptualized as a series of concentric rings used to defend a building and its occupants by providing them with sufficient notice to evacuate the premises and reach a place of safety while awaiting the arrival of firefighting personnel (Liston, 1999). According to Liston, "Protection managers use alarms that detect fires to evacuate people quickly and to call a firefighting service to extinguish the fire. Managers often connect these alerts directly to a public fire service organization to bring firefighting assistance as soon as possible" (1999, p. 204).

Although every building is unique and the fire alarm systems used will therefore differ in some respects, the types of alarms employed are typically tailored to the needs of their occupants. In buildings with general alarm notification requirements, an audible siren, bell, or alarm might be used to notify building occupants. As Liston notes, "Alarms produce an emergency or urgent sound that everyone in the building hears and recognizes to be a fire alert" (1999, p. 204). In most settings with access to reliable sources of electrical power, electronic bells or horns are used to alert occupants and, in the case of commercial properties, institutional staff and firefighting personnel as well. Liston further explains: "Automatic fire alarm systems are electrical systems of noise-making mechanisms such as bells or horns. This alerts the institution staff and the public to evacuate and firefighting staff to respond to extinguish the fire. The alarm system might send the signal outside the building to alert another fire service or security organization" (1999, p. 205).

Automatic fire alarm systems operate by detecting changes in environmental conditions that are indicative of a fire — such as elevated heat levels or airborne particulate matter — or other emergency conditions being monitored (Mork, 2002). The automation involved extends beyond simply notifying building occupants; it includes notifying institutional and firefighting staff and initiating automatic sprinkler and other deluge systems, together with appropriate notification and warning systems (Liston, 1999). According to Liston, automatic fire alarm systems are optimally tied to networks that can provide minimal response time. This varies from setting to setting, but well-designed systems can initiate fire suppression and notify appropriate personnel within three minutes. The best systems will also have persons on site as part of the response so that immediate steps can be taken to alert building occupants (Liston, 1999).

In cases where there are occupants with special needs — such as those who are hearing- or visually impaired — alternative notification methods have been devised in response to the Americans with Disabilities Act Accessibility Guidelines (ADAAG), issued in July 1991, which stipulate what types of building components and construction features define accessibility. According to Valente (1999), one provision of the ADAAG mandates that all fire alarm systems be accessible to building occupants. The various elements of a fire detection and alarm system that must be considered include manual fire alarm stations (pull stations), audible warning devices (horns and speakers), and visual warning devices (strobe lights), which are described in the table below.

ADA Accessibility Guidelines for Fire Alarm Systems

Table 1: Elements of Americans with Disabilities Act Accessibility Fire Alarm Notification Requirements

Manual Fire Alarm Stations: Where provided, these must be accessible. This requires the pull station to be installed so that the operating mechanism is no more than 54 inches above the floor when approach is available from the side by a wheelchair, or no more than 48 inches above the floor when the approach is straight on. Additionally, the pull station's design must be accessible, which requires that the activation mechanism be easily graspable.

Audible Warning Devices: Fire alarm horns and speakers are required to provide minimum audibility levels. The ADAAG requires a horn or speaker to provide an alarm sound level that is 15 dBA (decibels) above the prevailing sound level. However, if the prevailing sound level is greater than 105 dBA — which is considered damaging to hearing — then the alarm shall sound for 60 seconds at a level of 5 dBA above the prevailing sound level. In no case shall the alarm sound level exceed 120 dBA, whether intermittent or constant.

Visual Warning Devices: The ADAAG requires strobe lights to be installed in all general usage areas and any other area for common use. This includes restrooms, meeting rooms, conference rooms, dining rooms, hallways, lobbies, and cafeterias. In general, all areas of a building must be provided with strobe lights, with the exception of private offices, mechanical spaces, and exit stairs. The ADAAG allows strobe lights to be installed on the ceiling, but they must be suspended to meet height requirements and must flash at a rate of between one and three hertz (one to three times per second). These flash rates must be maintained to attract people's attention.

Source: Adapted from Valente, 1999, p. 47

Conclusion

The research showed that automatic fire alarm systems are used to provide building occupants and institutional staff with sufficient notice to safely evacuate premises in the event of fire or other emergencies. These systems operate by detecting changes in environmental conditions that signify the presence of fire or other emergency conditions, and by initiating steps to address those conditions — including the use of sprinkler and other fire suppression systems as well as notifying building occupants, institutional staff, and firefighting personnel. The research also showed that automatic fire alarm systems are increasingly being integrated into buildings' overall protection management systems, which include security, lighting, and HVAC infrastructure.