Heed Hazards of Clean & Dry Agent Systems

Fire/life-safety professionals need to learn risks before deploying clean and dry agent suppression systems.

This Installment is my concluding segment on suppression systems that a fire alarm practitioner may come across. In the past two Fire Side Chats I have reviewed wet, dry, preaction and deluge sprinkler systems, as well as low, medium and high expansion foam systems. I also provided a brief discussion on hypoxic air suppression systems. This month I will address a number of the clean and dry agent systems. This refers to the fact that water is not being used.

Warning, Carbon Dioxide Systems Can Kill
The first such method to cover is carbon dioxide systems. The installation standard for these systems is NFPA 12, Standard on Carbon Dioxide Extinguishing Systems. While effective, these systems can kill. The carbon dioxide replaces the air and oxygen in a space. If personnel are within the space and do not get out before the agent is released, they may die. There have been several cases in the past 10 years when such accidents have occurred, including one that happened during the testing of a fire alarm system.

The following caution is found within NFPA 12: In any use of carbon dioxide, consideration shall be given to the possibility that personnel could be trapped in or enter into an atmosphere made hazardous by a carbon dioxide discharge. Safeguards shall be provided to ensure prompt evacuation, to prevent entry into such atmospheres as described in, and to provide means for prompt rescue of any trapped personnel.

As a result of the accident that occurred during the testing of a fire alarm system, additional qualification requirements have been added to NFPA 72, The National Fire Alarm and Signaling Code, outlined under entry 14.2.6, Releasing Systems:

It is vital that prior to any work the fire alarm tech who may be installing or testing a system be aware that there is a releasing trigger, and the steps required to disable the releasing function. Testing personnel shall be qualified and experienced in the specific arrangement and operation of a suppression system(s) and a releasing function(s) and shall be cognizant of the hazards associated with inadvertent system discharge. Occupant notification shall be required whenever a fire alarm system configured for releasing service is being serviced or tested. Discharge testing of suppression systems shall not be required by this Code. Suppression systems shall be secured from inadvertent actuation, including disconnection of releasing solenoids or electric actuators, closing of valves, other actions, or combinations thereof, for the specific system, for the duration of the fire alarm system testing. Testing shall include verification that the releasing circuits and components energized or actuated by the fire alarm system are electrically monitored for integrity and operate as intended on alarm. Suppression systems and releasing components shall be returned to their functional operating condition upon completion of system testing.

It is vital that prior to any work the fire alarm technician who may be installing or testing a system be aware that there is a releasing trigger, and the steps required to disable the releasing function.

NFPA 12 (in Chapter 4) also covers specific requirements for the installation of detection devices. The detection protocol is different than for a typical detection system.

Other Effective Options to Explore
The next system type is the dry chemical. The requirements for these systems are found in NFPA 17, Standard for Dry Chemical Extinguishing Systems. These are typically hood suppression systems, with one of the more common providers being Ansul. Generally the fire alarm system is connected to an output within the extinguishing system. When the system is actuated, the dry chemical is released under pressure and the alarm point is triggered.

Caution should be taken when making the connection to the alarm system so as not to trip the mechanical actuator within the dry chemical system control box. These systems are also connected to the gas feed of a commercial kitchen, so that if there is activation, the gas is shut off.

The final system to mention is the clean agent system, covered in NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems. These are similar to carbon dioxide systems, but without the inherent danger when being within the space in which the agent is released. However, it would probably still be a good idea not to stick around. One of the first products that was used for these systems was halon. Halon is no longer allowed to be manufactured, but one can still purchase halon that was produced before the ban. All clean agent systems tend to be called halon systems, though this is simply not the case.

There are a number of agents that can be used, which is a decision of the designer. Attend any NFPA annual meeting and expo and you will find a number of these products being shown. Similar to NFPA 12 systems, there are specific requirements for detection.

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About the Author


Shane Clary, Ph.D., is Security Sales & Integration’s “Fire Side Chat” columnist. He has more than 37 years of security and fire alarm industry experience. He serves on a number of NFPA technical committees, and is vice president of Codes and Standards Compliance for Pancheco, Calif.-based Bay Alarm Co.

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