FAQs - Fire Performance

Answers to your most common questions about the fire performance of acoustical ceilings.

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What is flame spread and smoke developed? How does this relate to fireguard and class A?

Surface Burning Characteristics Rating (Formerly Flame Spread Rating)

The surface Burning Characteristics Rating of a material is a number, calculated from the results of a test, which indicates the relative rate at which flame will spread over the surface of the material as compared with flame spread on asbestos-cement board, which is rated 0, and on red oak, which is rated 100. Note that this rating is not the rate at which the flame actually spreads along the surface and is not at all an indication of the fire resistance of the material.

Test Method

The test used to obtain results from which a rating is calculated is called "Method of Test of Surface Burning Characteristics of Building Materials" (NFPA No. 255, ASTM E84, UL No. 723). It is commonly known as the Tunnel Test; the test equipment is referred to as the 25' tunnel. Although several small-scale tests have been developed to predict flame spread ratings based on the tunnel test, these are primarily bench tests for product development. The National Fire Protection Association (NFPA) has not accepted any alternate methods for determining the flame spread characteristics of materials to be used in buildings; for this purpose, NFPA recommends only the Tunnel Test.

The sample of material to be tested (minimum 18" wide, 25' long) is installed beneath the removable top panel. A gas flame is applied at one end and a regulated constant draft is directed through the tunnel from the flame end. The progress of the flame front along the sample is observed through side windows.

A flame spread rating is a relative number. It has no direct relationship to a fire resistance rating, which is a rating in hours determined by an entirely different test, known as "Standard Methods of Fire Tests of Building Construction and Materials" NFPA No. 251, ASTM E119, UL No. 263). The exposed surface (ceiling) of an assembly with a high (good) fire resistance rating; and, conversely, the exposed surface of an assembly possessing very little fire resistance could both have a very low flame spread. There is not necessarily any correlation between the two ratings.

There are numerous laboratories with 25 foot tunnels that do commercial testing.

Applying the Ratings

Relative figures on how fast fire will spread over the surface of the material allow fire protection engineers to deal with problems involving possibilities of (1) people being trapped within a building before orderly evacuation can be accomplished, and (2) rapid spread of fire through an entire building or area of a building before the usual fire protection measures can be put into effect to control or extinguish the fire. Building codes generally group flame spread ratings into classifications as follows:

Class 25 or Class I or Class A = Flame Spread Ratings 0-25; Class 75 or Class II or Class B - Flame Spread Rating 26-75; Class 200 or Class III or Class C - Flame Spread Rating 76-200; Class IV or Class D = Flame Spread Rating 201.

ASTM E119 and Fire Guard Products

ASTM E119 is an assembly test, not a product test. This is the test method (UL) used for fire resistance rated assemblies. UL does make note of this in the UL Fire Resistance Directory under INTRODUCTION. Therefore, any of our Fire Guard products have been tested according to this method.

Will ceilings alone provide me with a 1-hour rating?
No, Fire resistance ratings apply to a floor/ceiling or roof/ceiling assembly in its entirety. Individual components, such as ceiling panels or suspended grid systems, are not assigned fire resistance ratings. If your architect has not yet determined which UL design should be followed for your specific project, you may have to select a UL Design for code official approval. If so, here is how to select the correct UL fire-rated assembly:

  • Establish the hourly rating needed to meet code requirements.
  • Determine the existing or planned building elements, including structural, mechanical,electrical and finish materials, in the fire-rated assembly.
  • Refer to the Fire Resistive Rating Summary in the back of the Armstrong ceilings catalog to determine which UL design numbers resemble your building. The summary is divided into categories based on construction type and components.
  • Submit the chosen UL design to the code official for approval.

Which Armstrong ceilings and grid can I use if a fire-rated assembly is required?
Only Armstrong "FireGuard" ceilings and grid can be used in fire-rated assemblies. These products are identified by our FireGuard icon.

Are hold down clips necessary when following a UL design?
Armstrong Fire Guard ceilings do not require the use of "hold down" clips in a UL design. Hold down clips are only required for UL assemblies in which the ceiling panels weigh less than 1.0 lb./square foot. All Armstrong Fire Guard ceilings weigh 1.0 lb./sq.ft. or more and do not require hold down clips.

How do types BF, P and PC in UL designs relate to actual products?
PC=FINE FISSURED™ Ceramaguard® #605, #607 and #608
P=All other products designated Fire Guard

How do I obtain an hourly rating for a corridor?
Below is a list of construction practices used in the industry to obtain an hourly rating for a corridor:

  • If the corridor walls do not go to the deck, find the appropriate UL Design and install the specified fire-resistive ceiling and fire-resistive grid in corridor ceiling and adjacent areas.
  • If the walls in the corridor run to the deck above, find the appropriate UL Design and install the specified fire-resistive ceiling and fire-resistive grid in the corridor ceiling; fire-damp where walls are penetrated.
  • Install two layers of gypsum board in the corridor ceiling WITH CODE OFFICIAL APPROVAL, or reference the current 1997 Uniform Building Code section 1004. (2), page 1-115 Volume 1.

  The above construction practices should be reviewed with your local Code Official before construction.
How can I get a copy of the UL Fire Resistance Directory?
Call (847) 272-8800, Ext. 42612 or 42622, or write to Underwriter's Laboratories, Inc., Publications Stock, 333 Pfingsten Road, Northbrook, IL 60062. There is a cost for the directory, so inquire first.

How do grid types AFG, AFG-A, AFG-MX, FSL, FSLK, FST-6000 and FST-6000A relate to actual products?
AFG, FST-6000 = PRELUDE® XL® Fireguard
AFG-A, FST-6000A = PRELUDE Plus XL Fire Guard

Do you have any UL designs for your Drywall Furring System?
Yes, D501, D502, G523, G526, G527, G528, G529, J502, L211, L502, L508, L513, L515, L525, L526, L529, P237, P239, P241, P501, P506, P507, P508, P509, P510, P513, P514, P516.

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