Firestopping is an often misunderstood construction practice. This article aims to address what firestopping is and why it’s necessary in wall, floor and ceiling penetrations. But before delving into the details, let’s start by reviewing the two types of fire protection in structures: active and passive.

Active fire protection refers to fire protection systems that require some action in order to function. These include fire sprinklers, fire alarms, mechanical smoke evacuation, and fire extinguishers. Passive fire protection, based largely on the concept of compartmentation, refers to structures that are built into a building to passively prevent or stop the spread of smoke and fire. Passive fire protection consists of smoke dampers, fire-rated walls, and fire doors.

With all this protection, why are firestops needed? The trouble starts once electricity, water, HVAC and communications cabling and other amenities are added to the building. All of these require a contractor to penetrate the building’s fire-rated walls and floors, effectively “de-rating” their protection. To bring a wall or floor back up to its original fire rating, UL tested and certified firestopping materials must be installed around the pipes, HVAC ducts, cables, cable trays and other penetrants going through the hole. To do so, the contractor can take one of several firestop approaches, or apply a combination:

  • Intumescent products come in the form of sealants, putty, pillows, tape, sheets and strips, all of which expand when exposed to heat by as much as 25 times in volume while decreasing in density to form a high-strength, fire resistive seal. Intumescent firestop is used mainly around pipes and cables that penetrate through walls and floors.
  • Ablative firestop products are used to seal construction joints in a building where flames and smoke can spread, such as a gap between the floor and an exterior wall. Because joints are designed to allow movement, ablative firestop must be elastic to handle joint expansion and contraction, seismicity and wind loads, so they often are made from silicon. Ablative firestop absorb the energy of a fire to protect what is underneath, buying valuable time. They work by consuming heat energy from fire, and releasing it in the form of gases as they char to form insulation.
  • Firestop collars or chokes protect plastic pipes penetrating fire-rated walls and floors. They protect the integrity of the firewall by utilizing a heavy gauge galvanized metal collar to house a molded intumescent insert.
  • Insulative foil-encapsulated firestop products act as a barrier against heat and fire, helping to protect air, chemical and grease ducts by wrapping completely around them.
  • Lastly, endothermic firestopping protects through-penetrations, electrical cable trays, structural steel and emergency circuitry. Available in mats, endothermic materials release molecules of water in the form of steam when exposed to heat, therefore providing a cooling effect and acting as a heat sink. Endothermic products are sacrificial, that is, given enough time, they char away, crumble and disappear.

Mineral wool is often placed inside wall and floor cavities closed off by a firestop to assure the integrity of the fire rated seal. The wool is simply cut and stuffed into the penetrations prior to firestop being installed. Mineral wool is a critical component in perimeter fire containment, floor and wall penetrations, construction joints, and other applications.

It is important to note that when we speak of “firestopping” we refer to a system, not a single product. Firestopping has three elements: the fire-rated walls, partitions, floors or ceilings that have been penetrated; the cables, cable trays or conduits that make up the object creating the penetration; and the materials used to seal the penetrations to prevent the spread of fire and smoke. Firestop material is just one part of this complete system that, when used together, has an Underwriter’s Laboratory and/or ASTM approval. If one of the three elements fails, the overall system is compromised. 

Also, there is a common misconception that firestopping is the same as “fireproofing.” Not true. Fireproofing refers to the spray-on material on the underside of steel fluted decks in multistory buildings, steel I-beams, structural support columns and primary concrete. It typically is grayish in color with a rough texture. Fireproofing protects steel structures by insulating them from a high temperature fire, thus preventing the steel from warping, preserving its shape and strength.


Where There’s Smoke …

Firestops prevent the spread of flames. More importantly, it stops deadly gases and toxic smoke from traveling through walls, floors, ceilings and joints. Smoke and toxic gases are the leading killers of fire’s victims. Roughly 75 percent of building-related fire deaths are directly related to oxygen deprivation in the bloodstream, caused by the replacement of oxygen in the blood hemoglobin by carbon monoxide. During a fire, smoke can quickly travel a significant distance. In a developing fire, smoke will travel 50 to 100 feet per minute. In a fire that has developed, smoke may travel as fast as 300 feet per minute. The firestop is literally the last line of defense for building occupants and first responders.


Responsibilities and Ratings

There are many parties responsible for ensuring a building is properly fire-stopped, from the building owner, architect and specifier—all the way to the general contractor, sub-contractor and code official. Drywallers, HVAC technicians, electricians, plumbers and datacom installers run service installations throughout buildings. Every opening and gap they create must be firestopped to restore the integrity of a fire-rated assembly. 

Non-compliance can lead to serious legal issues. So, before walking away from a hole drilled into a wall, read what the National Fire Protection Agency, International Building Codes and National Electrical Code requires:

From the 2018 edition of NFPA 101:

  • 8.3.4 Penetrations.
  • Firestop Systems and Devices Required.
  • Penetrations for cables, cable trays, conduits, pipes, tubes, combustion vents and exhaust vents, wires, and similar items to accommodate electrical, mechanical, plumbing, and communications systems that pass through a wall, floor, or floor/ceiling assembly constructed as a fire barrier shall be protected by a firestop system or device.

From the 2018 edition of the IBC:

  • 706.9 Penetrations. Penetrations of firewalls shall comply with Section 714.
  • 714.2 Installation. A listed penetration firestop system shall be installed in accordance with the manufacturer’s installation instructions and the listing criteria.

From the 2017 edition of the NEC:

  • 300.21 Spread of Fire or Products of Combustion. Openings around electrical penetrations into or through fire-resistant-rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating.


Approved fire-stop materials are tested to ASTM E-814 and/or UL 1479, “Fire Tests of Through-Penetration Firestops.” Building materials are tested to the nearly identical ASTM E 119 and/or UL 263 test method, “Fire Tests of Building Construction and Materials.” Both evaluate the ability of a fire-resistive floor or wall assembly to perform its barrier function, resisting the passage of heat, flames, hot gases, and smoke in a fire situation. “Fire Tests of Through Penetration Firestops” or ASTM E 814 evaluates penetrations through a tested, fire-resistive (ASTM E 119 tested) wall or floor assembly. These standards contain the approved firestop system for building scenarios within the U.S. 

Although UL is the largest, best known and the go-to for approvals, they are not the only lab permitted to test building materials and firestop materials. Other third party labs can test to the ASTM standard and provide these approvals. Following are the testing standards for each specific purpose:

  • Fire Tests of Through Penetration Firestops
    • ASTM E-814
    • UL 1479
  • Tests For Fire Resistance of Building Joint Systems
    • ASTM E-1966
    • UL 2079
  • Fire Tests of Building Construction and Materials
    • ASTM E-119
    • UL 263

When it comes to the firestopping system requirements for your building, always consult the local authority having jurisdiction for guidance. The AHJ could be either your local fire marshal or building code inspector.


Firestop Listings

Like a fire-rated wall, a firestop must be “listed” and “labeled” for use as such and, just as with opening protectives, it must be rated to match the fire-resistance rating of the wall or another surface that is being penetrated.

In North America these ratings are typically listed as “F” ratings and “T” ratings. The F rating refers to the amount of time that it will take for a fire to break through from the exposed side to the non-exposed side of the fire-rated wall or assembly. The T rating refers to the time it takes for the penetrating item to heat to 325 degrees F plus ambient temperature. NFPA 101 requires that each of these ratings be no less than 1 hour and, again, they must at least match the rating of the barriers that protect the overall compartment. 

Additionally, an “L” rating shows the effectiveness of the firestop as a smoke and toxic gas barrier. It rates the air leakage in cubic feet per minute, per square foot of opening (CFM/sq. ft.). The “W” rating refers to water-resistant and/or water-tight seal. It indicates the effectiveness of the firestop material in restricting the flow of water through penetrations in ceilings, floors and walls occurring from exposure to the elements.

In some situations, particularly mechanical, electrical and plumbing 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.


Selecting Firestop Systems

To select the proper firestop system, there are several pieces of information that must be known:

Assembly type: What type of construction is being penetrated? Is it a wall, floor, or ceiling? Is it constructed of concrete, wood, or other material?

Penetrating item: What kind of item is being pushed through the wall? Is it electrical cabling, a metal pipe, a plastic pipe, an air duct, or a combination of items? Each of these items reacts differently during a fire. Knowing this will help you select the correct firestop products.

Required rating: What is the fire-resistance rating of the assembly being penetrated?

Size of the penetrating item: Firestopping a 2-inch pipe requires far different products compared to a large cable tray or grease duct.

Optional sleeve: In some assemblies, a steel sleeve is required while in others it is optional.

Cable fill: This refers to the size and types of cables that are being installed through the penetration.

Joint width and movement: A joint is a division that allows independent movement of the building. Knowing the width and movement requirements is necessary to choose the right system detail.

Annular space: This refers to the distance between the edge of the opening and the item penetrating the wall or floor.


Permanent or Temporary

When making an installation, the contractor has to decide whether or not the penetrations will be permanent for the life of the building. After all, things always change. For example, an expansion of a tenant’s office may require new electrical wiring due to workstations being added. Or a network may add new cable drops. Cable technology is always being upgraded to faster speeds, so it is more than likely a retrofit will occur every three to five years. Water pipes and HVAC ducts have to be moved in major renovations. In short, whatever is installed in the fire-stopped walls will likely be changed in the future.

Every time a cable is added or removed, the contractor must take out and replace the caulk, mortar or putty firestop just as they found it. Because this can be both messy and time-consuming, manufacturers offer products for jobs that require frequent re-penetration: Soft, pliable firestop bricks or pillows, and multi-plug pass-through systems let contractors easily remove and re-install cables.


What about Electrical Boxes?

This is a very common question. According to the International Building Code (IBC 2012 714.3.1), membrane penetrations (one-sided breaches) by electrical boxes may not require a firestopping assembly if they’ve been tested for use in a fire resistance rated assembly, and if they are installed per their listing or meet all of the following conditions:

  • The electrical box area does not exceed 16 square inches.
  • The aggregate area of openings through the membrane does not exceed 100 square inches in any 100 square feet of wall area.
  • The annular space between the wall membrane and the box does not exceed 1/8”.
  • If located on opposite sides of the wall, electrical boxes are separated by 24 inches in different stud cavities.

If these conditions are not satisfied, additional insulation, fireblocking, or listed firestop assemblies need to be added to achieve compliance with the code.

Final Thoughts

Modern firestopping has been around for 50 years, or to be more precise, since November 21, 1980. That is the date of the MGM Grand fire in which 85 people were killed and 679 injured, including guests, employees, and 14 firefighters. Burning material created toxic fumes that ascended throughout the hotel tower via vertical shafts and seismic joints, and caused the majority of the deaths. As a result of the fire, fire safety professionals and insurance companies became a driving force behind promoting and developing stronger building codes that require firestopping. While the importance of a firestop system is recognized today by experts in the field of fire safety, it needs to be a top priority among building owners and those involved in the construction industry. Firestop is a huge advantage to the builder, owner, and management because, if properly installed, it will greatly limit or eliminate the risk of fire, smoke and toxic gases spreading throughout an entire building, therefore preventing damage to the structure, personal property, and most of all, the lives within the building.