Ambient Attention
An array of conditions in industrial occupancies can affect the performance of a fire alarm system
by Wayne D. Moore
THE AMBIENT CONDITIONS PRESENT in industrial occupancies present challenges for the placement of detection devices and audible notification appliances for a fire alarm system. The 2016 edition of NFPA 72®, National Fire Alarm and Signaling Code, states the limits imposed on these devices based on ambient conditions, and designers must carefully consider those conditions when choosing components for a fire alarm system intended to protect an industrial space.
Those spaces can include conditions that can affect detector operation or initiate false alarms: mechanical vibration, electrical interference, process smoke, moisture, particulates, fumes, noise, and radiation, to name a few. Designers must investigate any of these sources of possible degradation and choose other detectors or mitigate the potential for smoke detector failure. While it might not be possible to completely isolate environmental factors, an awareness of these factors during system layout and design can significantly improve detector performance.
Additionally, ceiling height and shape can also affect smoke detector performance. The higher the ceiling, the greater the impact of the environmental effects on the smoke plume and on the ability of a smoke detector to initiate an alarm signal in the early stages of a fire. High ceilings mean designers must consider the possible impact of stratification, where the smoke plume has insufficient energy to drive it upward to the location of the smoke detectors. Altitude is also a factor; the greater the distance above sea level, the thinner the air, which can also affect a smoke detector’s ability to detect smoke particles.
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