Forty years ago, when John Kampmeyer started practicing engineering, through penetration firestops were very simple.

Editor's Note: Due to technical difficulties, Figure 1 noted below could not be reproduced online. Please refer to the print version in the January 2003 issue.

Issue: 1/03

Forty years ago, when I started practicing engineering, through penetration firestops were very simple. Once the opening through the fire barrier was made, and the pipe or other item was installed, the annular space was "stuffed" with a non-combustible material such as mineral wool, fiberglass, or heaven forbid, asbestos (this was before asbestos was known to be a carcinogen).

In 1975, a fire at the Browns Ferry Nuclear Plant demonstrated that it was not only important to seal penetrations to limit the spread of fire, but also to limit the spread of smoke. Previously used materials were found to be inadequate for this purpose. As a result of the fire, Dow Corning Corp. developed a silicone foam material which provided both a fire and smoke seal for penetrations. Subsequent to this initial development, a series of tests were developed for testing these materials in combination with various fire barrier constructions, resulting in the Underwriters Laboratories (UL) Fire Resistance Directory, containing 1,478 pages of through penetration firestop systems. Each system deals with a specific firestop material, penetrating element and construction system.

Determining the Fire Barrier Location and Rating

The first step in determining the proper firestop method to be used is to identify the location of the fire barriers and their hourly rating. In new construction projects, these are generally shown on the architectural drawings, or in the case where a fire protection engineer is part of the design team, a separate set of fire barrier drawings may be provided which show their locations and hourly ratings.

In existing construction, there may be little or no guidance from drawings. It is necessary to study the building and the local building code to determine the locations of the fire barriers. In multi-story buildings, each floor is generally separated by 1- or 2-hr. rated construction, although it could be greater in some cases. Shafts and stairs are generally separated by 2-hr. rated construction. Boiler rooms, incinerator rooms, storage rooms over 100 sq. ft., paint shops and maintenance shops will often be separated by 2-hr. rated construction. Enclosed corridors used for access to exits, separations between tenants and separations between dwelling units generally carry a 1-hr. rating, although in some cases these may be non-rated partitions in buildings which are provided with automatic sprinklers. Also, storage rooms under 100 sq. ft., trash chute access rooms, linen chute access rooms and laboratories are examples of rooms which may be separated by 1-hr. rated construction.

Institutional buildings such as hospitals and nursing homes have an additional requirement for smoke barriers to separate floors, so that patients can be moved to an area protected from smoke in the event of fire. These smoke barriers must also carry a 1-hr. fire resistance rating, so the penetrations through them must be protected with through penetration firestop systems.

One method that may be used, while not always accurate, is to look for labels on doors and frames that contain hourly ratings. Generally, the ratings of fire doors are as follows:

Door Rating Wall Rating

20 minutes 1/2-1 hr.

3/4 hr. 1 hr.

1 hr. 1 hr.

1 1/2 hr. 1 1/2-2 hr.

3 hr. 3-4 hr.

F, T and L Ratings

Firestop systems are tested in accordance with either ASTM E 814, Standard Test Method for Fire Tests of Through-Penetration Fire Stops, or ANSI/UL 1479, Fire Tests of Through-Penetration Firestops. These tests yield three ratings that are used in the published listings for the systems:

  • F Rating--This evaluates the time that the system will withstand the passage of flame and is expressed in hours.

  • T Rating--This evaluates the time that the system will limit the temperature on the unexposed side to not more than 325 degrees F and is also expressed in hours.

  • L Rating--This evaluates the air leakage through the system at ambient and/or 400 degrees F at an air pressure differential of 0.30" W.C. and is expressed in cubic feet per minute per square foot of opening (cfm/sq. ft.). The test for L Ratings is not a requirement of ASTM E 814 and is optional in UL 1479.

Both the 2000 Edition of the ICC International Building Code (IBC) and the 2003 Edition of the NFPA Building Construction and Safety Code require that penetrations through all fire barriers be protected with a through penetration firestop system having an F rating equal to the hourly rating of the assembly. NFPA includes the additional requirement that the F rating cannot be less than 1 hr. There is an exception in both codes that says where the penetrating items are 6" diameter maximum steel, copper or cast iron pipes, the annular spaces can be filled with grout to the full depth of the assembly. A T rating is not required for these assemblies because they are generally located above any combustible materials that could come in contact with the penetrating item.

For horizontal fire barriers (floors and floor/ceiling assemblies), both codes require additionally that the T rating of the through penetration firestop system has to be equal to the hourly rating of the assembly, except where the penetration is contained within a fire-rated wall or partition assembly. The additional T rating requirement is in recognition of the fact that many vertical pipes may come in contact with combustible materials that are on the floor of the areas where they are located. If it can be assured that there will be no combustibles near the piping, NFPA allows that the T rating requirement may be dropped.

Neither of the building codes call for an L Rating on smoke barriers at the present time. The only reference to a pressure differential is in the IBC, which requires the firestop system to be tested under a differential pressure of 0.01". The ASTM E 814 and UL 1479 standards require a 0.01" positive pressure as a minimum for all through penetration firestop system tests. This is done to assure that the system will withstand a fire pressure attempting to push the heat through it. It is typically more of an issue with non-metallic penetrating items where the fire could push through the burned off sections of piping.

Firestop System Identification

Once the required hourly ratings for the through penetration firestop system have been determined, the search for a specific system begins. Note that I am using the term system and not product. In order to determine the proper application of any product, it is necessary to know more about the construction of the fire barrier as well as the penetrating item. These three elements--fire barrier, penetrating item and firestop product--go together to form a system that makes up the through penetration firestop.

With 1,478 pages of these systems in the UL Fire Resistance Directory, this appears to be a formidable task. UL has developed an elaborate system of identification for these through penetration firestop systems that will serve to make the search for a particular system to be used on a project a little less difficult. This system consists of a three-component designation that identifies the area in the directory where a particular application may be found. This designation consists of the following components:


Type of Barrier

Fire Barrier Construction

Penetrating Item

Type of Fire Barrier

The first component is a letter that defines the type of fire barrier being penetrated and consists of one of the following letters:



C--Floor and/or Wall

Fire Barrier Construction

The second component of the designation is one or more letters, depending on whether the system is listed for horizontal fire barriers, vertical barriers or both. This designation breaks down as follows:

A--Concrete floors with a minimum thickness < or = 5"

B--Concrete floors with a minimum thickness >5"

C--Framed floors

D--Steel decks in marine vessels

E--Floor-Ceiling assemblies consisting of concrete with membrane protection

F-I--Not used

J--Concrete or masonry walls with a minimum thickness < or = 8"

K--Concrete or masonry walls with a minimum thickness >8"

L--Framed walls

M--Bulkheads in marine vessels

N--Composite walls

O-Z--Not used

Therefore, a through penetration firestop system with the designation C-AJ has been tested for concrete floors and concrete or masonry walls with a thickness < or = 5" for floors and < or = 8" for walls.

Penetrating Item

The last part of the designation is a four-digit number that identifies the penetrating item. The first digit in this number identifies the general type of penetrating item, and the remainder of the number is a specific designator for the through penetration firestop system. The designators are as follows:

0000-0999--No penetrating item

1000-1999--Metallic pipe, conduit or tubing

2000-2999--Non-metallic pipe, conduit or tubing

3000-3999--Electric cables

4000-4999--Cable trays with electric cables

5000-5999--Insulated pipes

6000-6999--Miscellaneous electrical items, such as bus ducts

7000-7999--Miscellaneous mechanical penetrating items, including air ducts

8000-8999--Combinations of penetrating items, including any combination of items listed above

System Selection

Thus, the search can be narrowed down to 1,000-2,000 possible choices. Each of these choices is very specific as to the size and type of penetrating items, as well as the details of the construction of the floor or wall being penetrated. It is necessary to study these details to be certain that the construction details in the listing meet the details of the fire barrier being penetrated before choosing a system to be used.

Figure 1 is a typical UL-listed through penetration firestop system. This system is listed under two UL designations:

--C-AJ 5021-F Rating-2 and 3 hr., T Rating-1/2 and 1 hr., L Rating-<1 CFM/sq. ft.

--C-AJ-5087-F Rating-2 hr., T Rating-1 hr.

While the above detail represents the firestop system, it is necessary to review the full UL listing to verify that all of the details of the system are in compliance. A review of the UL listing for these systems indicates that the main difference between the two systems is that the C-AJ-5087 system can be used with a sleeved opening up to 30" in diameter, while the C-AJ-5021 system is limited to a maximum 8" diameter opening. These systems illustrate a major problem facing designers in finding systems for floor penetrations using metallic pipes. It is difficult to get T Ratings that will equal the F Rating. This is because the metal transmits heat through the fire barrier at a greater rate than either the fire barrier construction or the firestop sealant, resulting in less time to reach the 325 degrees F maximum temperature. Generally, it will be necessary to use insulation on the piping, and you will still probably end up with an F rating greater than needed for the particular fire barrier. This is generally not as great a problem when using non-metallic piping because of the lower heat transmission rate.

Remember the steps in finding the firestop sealant needed for a particular project:

    1. Determine the type of pipe you will be using to penetrate the fire barrier.

    2. Determine whether you will be penetrating floors, walls or both.

    3. Determine the F, T and L Ratings you need or want to achieve.

    4. Determine the construction details of the fire barrier.

    5. Check the UL Fire Resistance Directory for a system that will meet your needs.

Happy hunting!