Hvac Systems And Fire Alarm Systems.pdf

ISC Fire Alarm Knowledge Base

HVAC Systems and Fire Alarm Systems What do fans and air moving equipment have to do with fire alarm/life safety systems? The supply and movement of air is a primary determinant of the severity of a fire event in a building. When a fire is well supplied with fresh air and its component, oxygen, the fire will be able to grow and spread more rapidly. Similarly, when an air handling system is carrying superheated air or smoke through fire walls and between compartments, the spread of the fire will be greatly enhanced. It is imperative that air movement be shut down in the event of a fire. Fire alarm systems are therefore interfaced to HVAC systems so that an alarm signal from the fire alarm system will cause the air handling systems in the area of the alarm to shut down. What is the purpose of fire alarm/life safety system control of HVAC functions? 1. To restrict the spread of smoke 2. To maintain fire resistive integrity 3. To minimize ignition sources 4. To permit air duct systems to be used for smoke control and removal Are there different rules for different types of buildings? There are variations of the rules or of the methods for monitoring and shutting down HVAC systems, but the basic concept is the same: When smoke or fire is detected in a system or in a fire compartment, the air handling equipment supplying that system or compartment shuts down. What code covers HVAC systems with respect to life safety? HVAC system code requirements, as they relate to fire alarm/life safety) are covered under the National Fire Alarm Code, the local building and fire codes, and the local HVAC/mechanical code. What happens to HVAC systems when an alarm is activated? The fire alarm sends a signal to the equipment that specifically controls the fans in the alarm area. These fans then de-energize, bypassing all HVAC control systems, thermostats, and any other environmental control equipment. The air supply to the fire and the possibility of transmission of smoke is greatly reduced. My fire alarm system sends a signal to my computerized energy management system, which in turns shuts off my HVAC. Is this OK? No. Most codes require that an HVAC shutdown signal bypasses and other computerized control system and directly operates the equipment that controls the fan, for the reason that a direct connection is simpler and less likely to fail or be accidentally reprogrammed.

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