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A firestop is a passive fire protection system made up of various components and used to seal openings and joints in a fire-resistance-rated wall or floor assembly. Penetrating cables are known as multi-cable transits (MCTs). Firestops are designed to fireproof a wall or floor assembly, impeding the spread of fire and smoke by blocking openings with fire-resistant materials.[1]


Firestops prevent unprotected horizontal and vertical penetrations in a fire-resistance-rated wall or floor assembly, which can diminish the fire-resistance rating of these structures and are the leading cause of rapid, erratic spreading of smoke and fire.[1]

Opening types[edit]

Firestops are used in:

  • Electrical, mechanical, and structural penetrations
  • Unpenetrated openings (such as openings for future use)
  • Re-entries of existing firestops
  • Control or sway joints in fire-resistance-rated wall or floor assemblies
  • Junctions between fire-resistance-rated wall or floor assemblies
  • Head-of-wall (HOW) joints, where non-load-bearing wall assemblies meet floor assemblies


Components include intumescents, cementitious mortars, silicone, firestop pillows, mineral fibers, and rubber compounds.


Firestops should be maintained in accordance with listing and approval use and compliance. Construction documentation sometimes includes an inventory of all firestops in a building, with drawings indicating their location and certification listings. Using this, a building owner can meet the fire code relating to fire barriers. Improper repairs may otherwise result, which would violate the fire code and could allow a fire to travel between areas intended by code to be separated during a fire.


It is often necessary to install new electrical cables or mechanical systems through a hole in a fire-rated barrier which has been firestopped during construction. In this case, the firestops are "re-entered". To maintain a building's original fire-protection plan, firestop re-entries must comply with the certification listing upon which the original configuration was based.

Spray fireproofing[edit]

Cable passing through a wall
Improper firestopping

Spray fireproofing of structural steel is best accomplished before interior partitions are built. Otherwise, a conflict with firestops in firewalls could result. Firestops must adhere to the bare, dry, unobstructed surfaces of the fire barrier which is penetrated (metal decking, for example), or adjacent to an interface of two fire barriers at which fire stopping is required (such as beams). Spray fireproofing cannot be applied before firestopping on these surfaces, since the fireproofing would obstruct adherence of the firestop materials to the fire-barrier surfaces. Spraying the upper room perimeter with fireproofing may also cover wall or ceiling joints and through penetrations which require firestopping. These joints are then not provided with proper firestopping, violating the integrity of the passive fire barrier.


Proper maintenance is enhanced by the installation of tags on each side of the firestop with information needed to refer to documents indicating approved procedures for the original installation and re-entries. This requires knowledge of the certification listing used for each opening of a building joint or a penetrant through-penetration seal.


Firestop materials are not rated per se. They receive a fire rating by combining materials in an arrangement specific to the item (a pipe or cable, for example) penetrating the fire-rated wall or floor and the construction arrangement of the fire-rated wall or floor. A two-hour-rated pipe-penetration firestop may consist of a layer of caulking over packed rockwool. The arrangement, not the caulking, provides the two-hour rating. The individual firestop materials and the overall firestop assembly are listed.

Testing and certification[edit]

Certification listings include those available from:

Regulations and compliance[edit]

When the installed configuration does not comply with the appropriate certification listing, the fire-resistance rating may be lower than expected. When it is difficult to assess the impact, it often must be assumed to be zero and the building's fire-protection plan is compromised. Each opening in a fire-resistance-rated wall or floor in a building must have a certification listing. There are thousands of listings from various certification and testing laboratories. The Canadian and United States Underwriters Laboratories publish books listing firestop manufacturers who have contracted with them for testing and certification. Firestops should be routinely inspected and maintained to mitigate the effects of time and re-entries.

Trade jurisdiction[edit]

In North America, composite crews are required when working near live electrical conductors; an electrician is required to observe and ensure the safety of the insulator. Germany's Gütegemeinschaft Brandschutz im Ausbau also offers a passive fire-protection course resulting in a Brandschutzfachkraft (Passive Fire Protection Expert) certificate. The material types used and the skill sets needed in insulation and firestop installations are similar. Exceptions to the rule that firestopping is insulators' work include firestop devices which become part of a plumbing system and which must be installed by plumbers during the forming of concrete.

Inadequate firestopping[edit]

No firestopping[edit]

Older buildings often lack firestops. A thorough inspection can identify all vertical and horizontal fire barriers and their fire ratings, and all breaches in these barriers (which can be sealed with approved methods).

Non-listed attempts[edit]

Firestops created by contractors or building maintenance personnel which are not listed, sometimes called "deemed-to-comply," are not credited with an adequate fire resistance rating for building-code compliance purposes. They are usually short-term, cost-cutting measures at the expense of fire safety and code compliance. One common error is citing a listing for a product which may be for another use. An insulation with an active listing of a certain flame-spread rating is unacceptable for firestopping purposes.

See also[edit]


  1. ^ a b "Fire Stopping: What Every Contractor Needs to Know | EC Mag". Retrieved 2017-09-06.
  2. ^ Approval Standard for Approval of Firestop Contractors, Class Number 4991

External links[edit]