|Emerging Trends in Firestopping|
Issue 7: Emerging Trends in Firestopping
By John Valiulis, P.E.
Firestopping is an overall term that is commonly used to describe four distinct features that are used to maintain the continuity of fire-resistance-rated assemblies:
There have been numerous advancements over the last few years involving firestop assemblies. This article describes some of those changes.
Penetration firestopping is mandated by all of the U.S. legacy building codes (National Building Code, Standard Building Code and Uniform Building Code), by the International Building Code1, as well as by the Life Safety Code2 and NFPA 5000.3 Because numerous individual factors can significantly affect the fire-resistance rating of a firestop system, there are now thousands of tested and listed firestop systems, covering a multitude of field conditions. A challenge therefore arises to sort through this selection to identify the suitable firestop system(s) for any given application. To facilitate this search, most major manufacturers now provide system selection aids on their Web sites, some of which include submittal of building capabilities. In addition, some manufacturers also provide software that can be installed on a PC or even a PDA, turning almost anyone into an instant firestop system selection expert.
Increased use of cast-in-place firestop devices
Cast-in-place devices (CIPs) are positioned on formwork before concrete is poured, resulting in a finished floor that contains pre-firestopped openings ready to accommodate piping or cabling. CIPs tend to be tested and listed for a broad range of acceptable applications, helping simplify specification and correct installation.
Sleeve firestop devices
Similar to CIPs are devices commonly referred to as "sleeve firestop devices" or "wall sleeves." These are premanufactured assemblies that incorporate a metal sleeve plus fire- and smoke-sealing materials. The materials may be preinstalled or packaged with the device in the right amount for installation after the penetrants are inserted. The materials are typically noncuring and are often flexible intumescents that allow penetrants to be easily removed or added. To accommodate installations where penetrants are already in place and cannot be threaded through, some of the sleeve devices open in a clam-shell manner. These features make them an increasingly popular option for cabling installations. This is in contrast to more conventional firestopping methods that involve the use of firestop sealants that typically cure and strongly adhere to the penetrants.
The current model codes and legacy codes mandate that floors that are required to be fire-resistance-rated must extend tight against exterior walls. To address the joint (gap) that usually exists between the edge of the slab and the inside face of a curtain wall, the legacy codes simply indicated that provisions must be made to maintain the fire resistance rating of the assembly at such locations.
In the 1990s, two listing laboratories, Omega Point Laboratories (OPL) and Underwriters Laboratories (UL), began performing evaluations of the joint between the floor slab and curtain wall using an intermediate-scale multistory test apparatus (ISMA). This two-story apparatus has an interior fire exposure on the lower floor and also adds an exterior fire exposure after five minutes to simulate flashover and the breakage of windows on the floor of fire origin. Since neither of these test labs sought ANSI accreditation for their very similar test methods, the 2000 edition of the International Building Code (IBC) specified the needed performance and referenced an ASTM E1194 time-temperature exposure.
Dozens of curtain wall firestop systems have been tested and listed for this application in the years since ISMA testing began. The application is referred to in the listings as "perimeter fire barrier systems." In 2004, ASTM committee E05 issued a method for ISMA testing (ASTM E23075), now referenced in the 2006 IBC.1 The 2006 IBC still permits continued use of listings obtained prior to the release of E2307 but conducted using the UL or OPL ISMA apparatus. One other listing laboratory has and continues to list joint systems based on a simple test using a gap between two slabs of concrete: Since neither the ISMA or ASTM E2307 methods are used, the local building inspector should be consulted to determine whether these listed assemblies meet the current requirements of the International Building Code.
Use of firestop specialty contractors
Increased inspection has shown that the process of individual trades firestopping their normal work as part of an "adjunct" service can increase the likelihood of deficiencies that later need to be corrected. To help resolve this problem, jobs are increasingly turning to the use of firestop specialty contractors to handle the firestopping of all joints and penetrations. Helping them do the job right, such contractors typically receive extensive training and support from firestop product manufacturers. This branch of specialty contracting has grown and gelled together. It has its own professional association (Firestop Contractors International Association), which provides continued training and development to increase professionalism.
Some accreditation organizations have also become involved with this progression. FM Global Research has been offering examination and accreditation of firestop specialty contractor firms through their FM49916 approval program for several years. Underwriters Laboratories has announced that they will enter the field in the very near future with their own firestop contractor accreditation program.
One hindrance to the widespread specification of FM4991-approved contractors has been the lack of a sufficient number of such contractors in most cities. As an alternative, some specifications are requiring that a firestop specialty contractor be accredited by the company that manufactures the firestop products used on the specific job.
The International Building Code1 mandates that the protection of penetrations and joints in fire-resistance-rated assemblies not be concealed from view before being inspected and approved. Such inspection has traditionally been performed by building officials. However, there is a move towards increased third-party inspection. Assisting in this evolution, ASTM committee E06 issued two standard guides in 2004 that standardize firestop inspection and reporting. They are ASTM E21747 for through penetrations and E23938 for joints and perimeter fire barrier systems.
When requested by the product manufacturer, the testing and listing laboratories perform an additional, optional air leakage test on firestop systems. The test is conducted at ambient temperature, as well as at 400°F (200°C), to evaluate the firestop system's resistance to the passage of "cold smoke" and "warm smoke." The result is reported in system listings as an "L-rating", with units of cfm/sq ft (m3/s-m2) for through penetrations or cfm per linear foot of joint (m3/s-m), as tested at a differential pressure of 0.3 inches water column (75 Pa). Because of the effectiveness of the typical joint-sealing process, the vast majority of joint systems have an L-rating of 1 cfm per linear foot (0.002 m3/s-m) or less. For through penetrations, values range from 1 to over 100 cfm/sq ft (0.005 – 0.5 m3/s-m2), depending the type of firestopping system used. This data can be useful to fire protection engineers, as it provides information on the volume of smoke that can be expected to migrate from a fire compartment based on the quantity and type of penetrations and joints, and the firestop systems used. The International Building Code1 has introduced an L-rating maximum of 5 for both joints and penetrations in smoke barriers.
Overall, the many changes in firestopping practice and products are aimed towards easier and more effective selection, installation and inspection, as a means of increasing the fire safety of a building while at the same time making it less onerous on the builder or building owner.
John Valiulis is Director, Codes & Standards, with Hilti, Inc.
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