A building is made of a number of fire-rated compartments. When these compartments are breached by various building service elements such as pipes and conduits, their fire-rating and ability to resist smoke migration is compromised. Firestopping, thus, is the process of installing third-party tested and listed materials into openings in fire-rated barriers to restore fire-resistance ratings. Building and fire codes, such as NPFA, ICC and European standards require that such rating be restored through firestopping. This article focuses on through-penetration firestops. In the next edition of International Fire Protection the focus will switch to construction joints and more advanced topics. This will include perimeter fire barriers (curtain walls) and challenging conditions found in the modern building environment, such as low voltage cabling, that should be taken into account when selecting the best firestop product and system.
Firestopping is the process of installing third-party tested and listed materials into openings in fire-rated barriers to restore fire-resistance ratings. This is usually a simple process when thought of ahead of time, but can become painful and expensive if done after the fact. Avoiding it altogether will put any type of structure at risk, even if it is protected by a sprinkler system.
Elements of a Firestop System
A through-penetration occurs when a service element breaches a fire-rated barrier. In Figure 1, the red object represents a conduit penetrating a fire-rated compartment. If the opening around the conduit is unprotected the fire has a path to propagate quickly into the adjoining space. Figure 2 shows a properly installed firestop system that seals the opening around the conduit and restores the fire-rating of the barrier. Fire and smoke are now contained to the compartment of origin.
For many people the notion of firestopping means red caulk around conduits or cables. But what good is a great “caulk” if the barrier cannot withstand the fire? Therefore, a firestop system starts with the fire-rated barrier itself, whether a floor or a wall, then the opening and what goes through it. Finally comes the firestop product installed into the opening as described by an Underwriters Laboratories (UL) classified firestop system, a Factory Mutual (FM) approved design, or as tested to the European standard EN 1366. The complete assemblage of elements, which is called a system, achieves the rating, not an individual product.
Tests for Through-Penetration
Firestops
For evaluation of through-penetration firestop systems, the base standard used is ASTM E 814, entitled Standard Test Method for Fire Tests of Penetration Firestop Systems. UL has a similar standard, UL 1479, entitled Fire Tests of Through-Penetration Firestops. In the United States, current building codes refer to both UL 1479 and ASTM E814. In Europe, the new standard is EN 1366, although individual countries may have their own legacy standards such as BS 476 in the UK or DIN 4102 in Germany.
UL 1479 exposes the test specimen to a standardised time-temperature curve, which ensures that all systems are tested to the same rigorous requirements in order to provide a benchmark. This curve is shown in Figure 3.
At five minutes, the furnace temperature is 538°C; at one hour it reaches 927°C. At two hours the temperature reaches 1010°C; at three hours it reaches 1052°C; and at four hours it reaches 1093°C. These are critically high temperatures, remembering that, aluminium cable conductors typically melt at 649°C and many plastics ignite at temperatures significantly below 538°C, that is within two or three minutes of the start of a fire!
F & T Ratings
Successfully passing tests to UL 1479 provides firestop systems with an F rating and a T rating. The F rating indicates how long, in hours, a firestop system has successfully prevented the passage of a fire. A two-hour F rating means the firestop system prevented fire spread for two hours.
The T rating is a measure of the thermal conductivity of a firestop system. This is the time required for various points on the unexposed side of the test assembly to rise 163°C over the starting ambient temperature.
Figure 4 shows an example of a UL test assembly consisting of plastic pipes installed in a concrete floor and protected with firestop collars.
The assembly is anchored to the test furnace. During the testing process, the firestop collars will expand through a process called intumescence: heat applied to the firestop material causes it to expand rapidly. In so doing, they close-off the openings and prevent the fire from spreading. Intumescent products are common in the industry and are particularly well suited for combustible materials, and are also frequently used on non-combustible materials as well.
The hose stream test (Figure 5) immediately follows the fire test and is designed to evaluate the structural integrity of the assembly. This is by far the most difficult segment of the test to pass. The red-hot assembly is blasted with a stream of cold water from a 64mm diameter hose discharged at high pressure. Not only does the assembly need to withstand the force of the water pressure, it also needs to withstand the strong internal forces developed from the thermal shock of rapid cooling. UL 1479 prescribes the pressure and duration of the hose-stream exposure, which depends on the hourly rating being tested and the size of the assembly. Firefighters should particularly be aware of the hose stream test as it gives an indication of whether a structure will withstand the back-draft effect. The thermal shock and force of applying a cold, high-pressure stream of water to a red-hot assembly is a good measure of system integrity.
To pass the hose stream test, the firestop system must prevent the passage of water to the unexposed side. It is important to remember that a building fire is a dynamic event. As pressure levels change and heat becomes more intense, surrounding structures and elements can fail, thereby stressing the firestop. The thermal shock of applying a cold, high-pressure stream of water to a red-hot assembly is a good measure of system integrity.
Testing to European standards is somewhat similar to that of ASTM/UL although the derived ratings are termed differently. However, the European standards evaluate only fire exposure and do not include a hose stream. This explains why European firestop systems often use mineral wool boards coated with a firestop spray or sealant; an approach that is not acceptable under ASTM/UL as it cannot pass the hose stream test.
L and W Ratings
Unlike ASTM E814, EN 1366 or BS 476, the UL 1479 standard includes two test protocols (conducted at the option of the test sponsor) for evaluating air leakage (L Rating) and short term water resistance (W Rating). The L Rating is used as an indication of smoke resistance. This will be addressed in the second part of this article in the next edition of International Fire Protection.
FM Approvals
In some situations, particularly mechanical, electrical and plumbing (MEP) applications in industrial plants insured by FM Global, it is necessary to have FM approved firestop installations. This usually requires two types of documents: one showing that the manufacturer is subject to FM’s quality inspection program, and one proving that the firestop system is tested under UL/ASTM standards.
When there is No Test
There will be situations when a manufacturer has no test for a specific application. In such a case, an engineering judgment (EJ) is permitted under strict conditions defined by the IFC (see below). The key to an EJ is that it must be issued by qualified personnel, usually a company engineer or a third-party engineering company, but never a sales person. It must also be based on credible testing. For example, issuing an EJ for a large plastic pipe based only on a test for small plastic pipe is not acceptable.
The UL Mark
Products tested at UL provide a very important piece of quality assurance through the presence of what is called the UL Mark. That is the guarantee that the composition of the product the manufacturer sells is the same as what was tested. This is achieved through a series of unannounced and continuous inspections conducted by UL throughout a manufacturer’s productions facilities worldwide. Even the ISO certification does not provide such an independent assurance, and it is a requirement that the EN 1366 standard is trying to emulate.
Where to Go for Help
Firestopping is a specific and often misunderstood construction practice. Quality firestop manufacturers offer assistance to designers, inspectors and end users, usually free of charge and available by telephone, fax or e-mail. Many publish valuable information including firestop designs, product information and other informative articles online on their websites. Most manufacturers staff the telephone lines with degree-qualified engineers. In my company, these same people (some 15 of us around the world) have a hand in product development, from early concept to third-party testing. The ability to contact manufacturers’ technical personnel directly represents a huge advantage to the end-user. Their wealth of knowledge can only assist in getting the job done efficiently and, most importantly, correctly. Serious manufacturers of firestopping products also have trained field personnel that can help on job sites and visit with users.
Additionally, organisations such as the International Firestop Council (www.firestop.org), a not-for-profit organisation of manufacturers, distributors and installers, services the construction industry by publishing valuable information and working with industry professionals to increase awareness of proper firestop practices. Similarly, the Firestop Contractors International Association (www.fcia.org) is an excellent source of information and contractors trained to the highest standard by being FM4991 approved or UL qualified.
Of course, when it comes to better understanding the specific code requirements of an individual construction project, always contact the local Authority Having Jurisdiction (AHJ). The code official has a clear understanding of building requirements and experience gained from a multitude of similar construction projects.
Summary
Firestop systems, not individual firestop products, achieve ratings based on evaluation to the appropriate standards described herein. A firestop system (and firestop product) is only as effective as the manner in which it is installed. A good installation will be consistent with the characteristics described in the firestop system. A well thought out selection of a firestop product will ensure the building’s needs are maintained as the various service elements are changed or expanded. Unfortunately a firestop system can be rendered ineffective if installed (or reinstalled) improperly. Installation practices considered improper include inappropriate mixing of products, using materials other than those tested as part of a firestop system, not following the parameters of a firestop system, and of course penetrations that are not protected at all or where protection has been removed or reduced over time. Such a system has no integrity and presents a safety hazard rather than being an important component of a building’s life-safety system.
For further information, go to www.stifirestop.com
About the Author
Christopher DeMarco Manager of Technical Services and Applications Engineering at Specified Technologies Inc
