By: Grace Gallagher

Building fires can have devastating effects on occupants, businesses in or near the building, and first responders, especially if a building envelope inspection hasn’t been periodically carried out. A building fire is often the preventable result of improper construction methods or incorrect use of a building’s mechanical or electrical systems. Unfortunately, the occurrences that lead to fire are not always easy to detect or predict. In these cases, firestopping systems can be the difference between a disastrous fire that spreads quickly through a building, or flames and smoke that are contained to a confined area and more easily extinguished.

Firestopping is a method of sealing holes, penetrations and joints in fire-rated walls and floors to contain flames and smoke within the space in which they originated. Firestopping systems are meant to minimize the risk of fire and smoke spreading throughout a building, to protect means of egress, and to provide enough time for first responders to quench flames and attend to building occupants. Although the installation methods and materials may differ from system to system, all firestopping systems consist of three things: a fire rated wall or floor; an opening, penetration, or joint located along the wall or floor; and materials used to fill the opening, penetration, or joint. Firestopping systems are rated by the Underwriters Laboratory (UL) based on how long the system can withstand a fire, how quickly the temperatures rise in spaces adjacent to the fire, the amount of air that passes through the seal, and the water-tightness of the seal. It is important to note that firestopping systems, not firestopping materials, are classified as “fire-rated.” Firestopping materials by themselves are not rated to prevent the spread of smoke and flames; they must be correctly installed within a hole, penetration, or joint through the fire-rated wall or floor in order to be effective.

There is a range of firestopping materials and assemblies for the different types of penetrations that must be sealed. Intumescent materials expand upon exposure to heat to insulate and seal the opening. Endothermic materials release chemically-bound moisture when exposed to heat, dampening the fire and flames close to the opening. An ablative firestopping product will act as a sacrificial “layer” that will burn away slowly to delay the spread of the fire, and heat sinks absorb and dissipate heat away from the penetration. In addition, mechanical devices can be used to block larger openings such as doorways, or electrical and plumbing penetrations through fire-rated walls. Firestopping materials come in many forms, including sealants, putties, mortars, sprays, wraps, pillows, blocks or mechanical devices, and can be used in conjunction with a packing material such as mineral wool to seal the opening in which they are being installed.

Firestopping systems can effectively prevent the spread of smoke and flames only if they are correctly installed and maintained. Installers should take care to ensure all voids in the penetrations or joints are filled and that sealant, mortar, or spray firestopping materials are evenly applied with no gaps. Putties, wraps, blocks, and mechanical devices should be installed according to the manufacturer’s and engineer’s specifications. Firestopping systems must be inspected at the time of installation and at least once per year by the building owner; they should be replaced if they are found to be deficient. Common deficiencies include voids and gaps in the firestopping material, or incorrect installation of the materials used.

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