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Know your fire codes

Safety & Codes | October 1, 2012 | By:

By Edward J. Kaminski

Q: Which fire codes apply to which types of temporary structures?

A: When a permit applicant approaches the fire department for permits to erect a temporary structure, the first thing to determine is how that structure should be classed. Some requirements of the 2012 International Building Code® and International Fire Code® differ depending on whether the structure is a temporary “membrane structure” or a “tent”—and neither code covers a structure that is deemed to be a temporary “building.”

According to Section 202 of the 2012 International Fire Code, a membrane structure is defined as an “air-inflated, air-supported, cable or frame-covered structure as defined by the 2012 International Building Code and not otherwise defined as a tent.”

A tent is defined as a “structure, enclosure or shelter, with or without sidewalls or drops, constructed of fabric or pliable material supported by any manner except by air or the contents that it protects.”

Difficulties in classifying structures can arise because a tent can be supported by any manner except air, and a membrane structure can also be a frame-covered structure. Some jurisdictions, including Clark County, Nev., consider all structures with fabric sides to be tents even if they are also frame supported. The fire-code related impact of the classification is that tents require larger exits than membrane structures. The 2012 International Fire Code Commentary cites a deadly circus tent fire in 1944 as the reason for the larger minimum exit widths for tents as compared to membrane structures. It could be argued that tents are expected to have flaps (fabric covered openings) rather than conventional side-hinged swinging doors. Regardless, tents used for assembly occupancies usually have neither an automatic fire alarm system to help detect a fire and initiate evacuation, nor a fire sprinkler system to initiate early suppression of a fire.

The 2012 International Fire Code requires automatic sprinklers in most assembly occupancies that exceed 12,000 square feet or having an occupant load exceeding 300 persons. Use Group A-2 of the code, which includes drinking establishments, has a sprinkler requirement threshold of 5,000 square feet or an occupant load of 1,000 persons. Some jurisdictions have amended their fire codes to even smaller sprinkler threshold values. Likewise, a manually activated fire alarm system is required when the occupant load exceeds 300 persons.

Structures that have either metal-framed glass walls or composite plastic walls with a membrane fabric roof are classified as temporary buildings and not anticipated within Chapter 31 of the 2012 International Fire Code. These types of structures appear in expositions and trade shows and may only be in place for a week or so. Permit applicants often seek relief from building and fire code requirements due to the temporary nature. Although the building is temporary, the potential for a fire or other emergency event is the same or greater in a temporary building.

Many building departments will not inspect or issue permits for temporary buildings. In this case, the Authority Having Jurisdiction will be the fire department, and the fire safety requirements for erection of the temporary building will have to be individually negotiated.

By Edward J. Kaminski, P.E., Clark County Fire Department, Las Vegas, Nev.

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