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Understanding the Basics of Firestopping

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.


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!

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