Putting Up Barriers
Protecting (and being able to define) hazardous areas
NFPA Journal®, May/June 2013
There are plenty of myths and misconceptions out there about what constitutes a hazardous area. Based on what I’ve heard people say in seminars, it seems that some of them are content to go with what they think they know rather than looking it up in the code. That’s why janitor closets, electrical closets, and fan rooms can sometimes be perceived as hazardous areas, when in fact none of them are.
The protection of hazardous areas varies throughout the different occupancies covered by NFPA 101®, Life Safety Code®. Each occupancy chapter includes a list or description of what constitutes a hazardous area in Section 3.2, “Protection from Hazards.” These are not all-inclusive lists, but rather a collection of well-known hazardous areas for each particular occupancy. Some of the occupancy chapters provide details on how to protect specific hazards, while other chapters simply refer back to Section 8.7 for the protection requirements.
Section 8.7, “Special Hazard Protection,” addresses the protection of hazardous areas and provides three protection options. The first is to enclose the space with a one-hour fire resistance rated fire barrier, including a three-quarter-hour fire protection-rated door. The second option requires that the area be protected with an automatic extinguishing system — this would usually be sprinklers, but it could be any automatic extinguishing system.
If option two is used, the code requires that the space be enclosed with a smoke partition in accordance with Section 8.4, “Smoke Partitions.” Smoke partition walls do not require a fire resistance rating, but they must not have openings that would permit the transfer of smoke. To limit the transfer of smoke, doors in the smoke partition walls do not require any fire protection rating, but they do require a self-closer so that the automatic extinguishing system will control the fire and the smoke partition enclosure will contain the smoke and products of combustion.
Section 8.4 states that the smoke partition walls may stop at an acoustical tile suspended ceiling. An annex note indicates that such a suspended-grid acoustical tile ceiling — even with air system supply and return-air diffusers, speakers, and recessed light fixtures — is capable of limiting smoke movement. If the space above the ceiling is used as a return air plenum with open return air grilles in the ceiling, then obviously the ceiling cannot limit the transfer of smoke. Also, it is important to note that the Life Safety Code includes the similar terms “smoke partitions” and “smoke barriers.” Generally, smoke barriers are more substantial than smoke partitions. Smoke partitions are addressed in Section 8.4, and smoke barriers are addressed in Section 8.5.
In the third protection option, for hazards considered severe or where required by the occupancy chapter, both the one-hour fire resistive enclosure and the automatic extinguishing system are required. This raises the question of what constitutes a severe hazard. The term “severe hazard” is not defined in Chapter 3 of the code. An annex note for Chapter 18 states that, for example, the “hazard level of a laboratory is considered severe if quantities of flammable, combustible, or hazardous materials are present that are capable of sustaining a fire of sufficient magnitude to breach a one-hour fire separation.” Hazard levels in occupancies other than laboratories will require evaluation by the authority having jurisdiction.
In addition to the types of general hazardous areas described here, the code also addresses other special hazards such as explosion protection (8.7.2), flammable and combustible liquids and gases (8.7.3), and laboratories (8.7.4). General mechanical rooms containing only fans or water pumps are not considered hazardous areas, nor are typical electrical rooms.
Chip Carson, P.E., is president of Carson Associates, Inc., a fire engineering and code consultancy.