What Is Firestopping?
As a cable installer, your job involves drilling holes in walls and fire-rated barriers for cable pathways. Smoke and fire spread through the holes that are not resealed.
The holes in fire-rated barriers must always be resealed to reestablish the original fire rating of the barrier. Firestopping is the process of installing qualified firestop materials in all penetrations created during the installation of communication cables.
The cable installer is responsible for using both approved firestopping methods and approved materials.
Most people died in building fires die from toxic smoke and gases, not from direct flames. Firestop systems must be installed in commercial buildings to prevent toxic smoke and gases from travelling through building penetrations.
Consider these fire statistics.
- 3/4 of all fire deaths are caused by smoke inhalation.
- Approximately 57% of people killed in fires are not in the room of the fire’s origin.
- Visibility – 47% of survivors caught in a fire could not see more than 12 feet.
- Smoke travels 120-420 feet per minute under fire conditions.
The following picture shows the areas that allow for fire/smoke spread.
There are two types of wall and fire barrier penetration types.
1) Through penetration
A through penetration is a hole that passes completely through a fire-rated barrier. It can be a hole cut into a concrete floor to install a conduit or a hole cut through a fire-rated wall.
2) Membrane Penetrations
A membrane penetration is a partial penetration in a wall or a single surface fire barrier penetration. A hole in one side of a wall to install a telecom outlet is a sample of membrane penetration.
How Do Firestop Products Work?
1) Through-penetration firestop products work by filling the voids around penetrating items in fire rated walls and floors.
2) Some firestop products intumesce or expand in the presence of heat.
3) The intumescing action seals and stops the spread of flames and smoke to other floors and rooms for penetrations that melt or change shape in a fire. (eg. Plastic pipe)
Firestopping Standards and Rating Classifications
Firestop materials used in a firestop system must be tested to pass the following standards.
- American Society of Testing Material (ASTM) E814
- Underwriters Laboratories (UL) 1479
The testing and approval comes from a certified and independent laboratory.
The three ratings for through penetration firestop systems in USA include the following.
1) F Rating (Flame Ratings)
F rating is required for all through penetration firestop systems. It is measured for passage of flame.
It is usually expressed in hours indicating a specific length of time that a fire-resistive barrier can withstand fire before being consumed or before permitting the passage of flame through an opening in the assembly.
This rating also evaluates if a fire occurs on the opposite side of the barrier from heat transmission through the firestop.
F rating also evaluates if an opening occurs in the firestop due to the hose stream. This rating looks for the projection of water beyond the exposed side of the firestop.
2) T Rating (Thermal Ratings)
T rating is required for all through penetration firestop systems. It is measured for fire and temperature.
T rating is usually expressed in hours indicating the length of the time that the temperature on the non-fire side of a fire-rated barrier does not exceed 325ºF above ambient temperature.
3) L Rating (Smoke Ratings)
The L rating is based on the amount of air and smoke leakage. It measures the amount of air (or cold smoke) that can leak through a penetration and the number indicates the amount of air in cubic feet per minute.
L rating is an optional part of the UL 1479 standard and not included in the ASTM E814 standard.
The L rating is conducted under a differential pressure of 0.3 inches water column (75 Pa) at 75ºF and 400ºF.
Firestop systems are made up of a combination of products to reestablish the original raging of a penetrated fire barrier. It can be made of a single material or a combination of materials that provide a balance of
- Heat resistance
- Adequate sealing at extreme temperatures
- Durability to stay in place and stay intact during a fire
- Structural integrity to survive the erosive effects of a high-powered hose stream
Firestop products have unique properties that make these materials desirable in the event of a fire. The characteristics can be one or more of the following.
- Endothermic products can absorb heat. They are used with a fire-rated barrier and flammable materials are located on the opposite side of the barrier.
- Intumescent products can swell and become enlarged due to heat. They are used if a cable or conduit burns away during a fire and leaves a hole in the firestop. Intumescent firestop products will block the hole.
- Ablative products can develop a hard char when exposed to heat. This helps it resist erosion from flames and super-heated gas. Ablative products remain pliable until heat is present. This makes them ideal for where cables are continually added to a building. When exposed to heat, the hard char will prevent fire, smoke, and gases from passing through the firestop.
1) Mechanical Firestop Systems
Mechanical firestop systems consist of pre-manufactured products and devices that are pre-shaped and sized to fit into or around standard penetrations made by conduits, cables, core holes, and other penetrations commonly found in commercial buildings.
They fit and expand into standard sized building openings and are secured and held into place by tension.
2) Non-Mechanical Firestop systems
Non-mechanical firestop products are designed to fit and expand into non-standard building openings. They can fit into irregularly shaped or irregular size openings.
Non-mechanical firestop products include the following products.
Firestop Putties. Firestop putties provide intumescent properties that will swell around the installed cables. Many firestop putties also have the abilities to absorb heat which makes them pass T ratings. Firestop putties usually remain soft and pliable until exposed to heat. This allow reentry into a firestopped cable pathway for adding new cables or removing old cables.
Firestop Caulks. Firestop caulks are preferred for very large openings that must be firestopped. They are usually dispensed from large pails or smaller caulking tubes. They are available as latex compositions, water-based compositions, and solvent-based compositions.
Firestop Silicone Foam. Firestop silicone foam expands when exposed to heat and is capable of easily sealing large openings. When exposed to heat, firestop silicone foam forms a cellular structure that blocks fire, flames, and smoke.
Independent Inspection of Firestops
If so much time is being spent on the installation quality through programs like FM 4991, then why is an independent inspection agency needed to oversee installation even if a professional firestopping contractor installs firestopping?
Over the past few years, firestop industry participants have been frustrated by some firms who don’t take the time to install firestopping properly.
Jess Kray, professional engineer, Kray Cabling, Inc., Richmond, Calif., in an editorial published in The Electrical Distributor magazine, stated, “I see poor or no firestopping all the time. In fact, I have never seen a building that was properly firestopped throughout.” When there are many trades trying to install firestopping, anything can happen. Some firms pay attention to the firestop installation protocol while others may not fulfill the obligations that a life safety system deserves.
Currently in our industry, there are four methods of installation for firestopping a project. First, a specialty firestop contractor may be hired by the general contractor (GC) or owner to install the complete scope of work. Second, the GC/owner may split the scope of work to penetrations only and wallops/joints/perimeter fire protection. Third, penetrations might be handled by the trades making the penetration, while perimeter, walltops and joints are installed by a professional firestop specialty firm. Fourth, the GC/owner lets the trades decide how to divide the work. As a result, some trades hire specialty firestopping contractors, while others handle firestopping on their own. On some projects, this decision leads to all trades installing their own firestop scope of work. Conceivably, more than eight different trades could be installing firestopping on a project. This is especially true when “he or she who pokes holes, fills them” is the chosen firestopping method.
This latter “freewheeling” method of purchasing has caused firestopping to become difficult to manage. How can eight trades use only one manufacturer’s tested systems to firestop a building? Such cooperation is difficult at best. Then, if eight product manufacturers are used, will inspection personnel be able to identify which product/system is which during testing? From what industry observers, architects, engineers, code/fire officials, building owners report, this type of procurement method is the most difficult to control. They credit this difficulty to the vast number of trades responsible for firestopping. And, in the event of a subsequent disaster due to poor firestopping, assigning responsibility can be difficult as firms hide behind each other to evade blame.
A situation where multiple trades are responsible for firestopping work is a clear-cut example of why independent inspection should be required. ASTM E 2174, “Standard for the Inspection of Through Penetration Firestop Systems,” outlines a protocol for the inspection group to follow when quality control checking a project.