​Ceiling Performance FAQs

1. What is NRC?
   NRC means Noise Reduction Coefficient. It is the average sound absorption coefficient measured at four frequencies: 250, 500, 1,000, and 2,000 Hz expressed to the nearest integral multiple of 0.05. It is measured in accordance with ASTM C423 and rates the ability of a ceiling, wall panel, or other material to absorb sound. The NRC is averaged over all angles and sound frequencies, and represents the average absorption per unit area. The NRC ranges from 0.00 (concrete floor) to 1.00 (high performance acoustical products like OPTIMA).
2. What is CAC?
   CAC means Ceiling Attenuation Class. It is a single-number rating that represents a ceiling system’s efficiency as a barrier to airborne sound transmission between adjacent closed spaces that share a common air plenum. This is a 2-pass test – sound will radiate through the source room’s ceiling as well as the receiving room’s ceiling as defined by ASTM E1414.
3. What is NIC?
   NIC means Noise Isolation Class. It is a single-number rating calculated in accordance with ASTM E413 using measured values of noise reduction. Whereas STC, CAC, and NRC are laboratory measurements of material performance, NIC provides an estimate of the total sound isolation between two enclosed spaces that are acoustically connected by many paths.
4. What is AC?
   AC means Articulation Class. It is a single-number rating for the performance of a ceiling in an open office with a partial-height divider. Defined by ASTM 1111, the attenuation of sound that travels over a divider and reflects off of the ceiling is measured at human speech frequencies. Ceilings best suited for use in the open office have AC values of 170 or greater. A standard acoustical ceiling (NRC 0.55) will normally have an AC of 150. Non-absorptive materials, such as gypsum board, will have an AC of 120. The highest AC that can be achieved by a ceiling is 230.
5. What is Sabin?
   Sabin is the unit of measure for total sound absorption of an acoustical object. For items like baffles, clouds, and canopies the entire object is tested and the acoustical absorption of each object is measured. For continuous ceiling material the total absorption is measured but it is divided by a known surface area producing absorption coefficients.
6. What is the difference between STC and CAC?
   STC means Sound Transmission Class. It is a single number rating corresponding to the sound reduction from one side of a barrier to the other. The STC is used to rate the performance of walls, partitions, windows, etc. For this test sound is passing through the material once – from one side to the other. In a CAC test sound passes from a source room, through the ceiling plane, across a shared air space and then through the ceiling plane of the receiving room.

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1. 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.

2. Will ceilings alone provide me with a one-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.
3. 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 FIRE GUARD icon.
4. 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 FIREGUARD

5. 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 1004.3.4.3.1 (2), page 1-115 Volume 1.

   The above construction practices should be reviewed with your local Code Official before construction.

6. 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.

7. 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 FIRE GUARD
   • AFG-A, FST-6000A = PRELUDE Plus XL FIRE GUARD
   • FSL = SILHOUETTE XL FIRE GUARD
   • FSLK = SUPRAFINE XL FIRE GUARD
8. 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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1. Which grid products can be used for seismic applications?
   Since ceiling panel performance is not well defined in the IBC requirements, Armstrong has partnered with the State University of NY at Buffalo to test both standard and non-standard ceiling systems for seismic performance. The results of more than 70 full-scale seismic tests offer proven safety and performance support for standard and non-standard ceilings, flexible design options, and more efficient installation designs.

   The following grid systems have been tested and approved for International Building Categories (IBC) A-F:

   Suspension System	IBC A, B, C	IBC D, E, F
   AL PRELUDE Plus XL	X
   SS PRELUDE Plus XL	X
   CLEAN ROOM	X
   INTERLUDE XL	X
   PRELUDE Concealed	X	X
   PRELUDE ML	X
   PRELUDE Plus XL FIREGUARD	X	X
   PRELUDE XL	X	X
   PRELUDE XL for Exterior Applications	X	X
   PRELUDE XL FIREGUARD	X	X
   SILHOUETTE	X	X
   SUPRAFINE ML	X
   SUPRAFINE XL	X	X
   SUPRAFINE XL FIREGUARD	X	X
   Drywall Grid System	X	X
   SHORTSPAN	X	X

    

2. What do I need to know to be able to install ceilings to meet seismic requirements?
   You need to know the following:
   • With what code are you being asked to comply?
   • With what seismic zone or category are you being asked to comply?
   • What implementation standard will be used/accepted?
3. Is there a step-by-step installation procedure for seismic requirements?
   Common implementation standards are IBC, UBC 25-2 and ASTM E 580. The implementation standards are straightforward. Please contact our TechLine department at 877-ARMSTRONG if additional assistance is required.
4. How do I know what code my state or local municipality has adopted?
   Contact your local government office and ask to speak to someone about building permits and construction requirements.
5. Is there an installation alternative to 2” wall molding in IBC seismic categories D, E and F?
   The Armstrong BERC2 system offers the alternative of 7/8” wall molding and no perimeter stabilizer bars (versus 2” wall molding with perimeter stabilizer bars) with verified performance and superior aesthetics. The BERC2 system complies with IBC as an alternative material or method with code official approval. Section 104.11 of the IBC code provides for “Alternative materials, design, and methods of construction and equipment.” Section 104.11.1 authorizes building code officials “to require tests as evidence of compliance” in order to substantiate claims for alternative materials or methods.
6. If the code requires 2” wall molding, how can Armstrong offer an alternative using 7/8” wall molding?
   The Armstrong BERC2 system was full-scale tested on a seismic table at the Structural Earthquake Engineering Systems Laboratory at the State University of New York at Buffalo. The appropriate section of the IBC code (Section 104.11) allows code officials to consider alternative construction methods. The BERC2 system solution is an “alternative construction method” properly governed by IBC section 104.11. Full-scale tests conducted validated that the BERC2 system performs in a manner consistent with the requirements of the 2000 IBC.
7. What documentation can I provide to a code official to prove the BERC2 system has demonstrated proper seismic performance?
   The IBC code authorizes code officials to approve alternative construction methods based upon acceptable full-scale test results. Armstrong has made these test results available to you for code official to review. Test summaries and seismic literature can be found on our web site. Complete test results can be obtained by calling TechLine at 1-877-ARMSTRONG (276-7876).

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1. How do the ISO/TC209 clean room class ratings compare to the Federal Standard 209E clean room class ratings?
   ISO/TC209 clean room class ratings have replaced the Federal Standard 209E ratings. ISO/TC209 is based on metric measurements versus Federal Standard 209E which is based on imperial measurements. See comparison chart: ISO FED STD 209E 3 1 4 10 5 100 6 1,000 7 10,000 8 100,000
2. What do the clean room class ratings mean?
   The classes, according to ISO/TC209 14644-1, are a level of airborne particulate cleanliness. A Class 5 means that less than 3,520 particles (0.5 microns in size) are present per cubic meter, which equals 100 particles per cubic foot. A Class 6 indicates less than 35,200 particles per cubic meter. The higher the class number, the more particles present.
3. What products do we recommend for clean room applications?
   CLEAN ROOM FL, CLEAN ROOM VL, HEALTH ZONE OPTIMA and HEALTH ZONE ULTIMA non-perforated ceilings, installed on 1-1/2" or 15-16" Co-Extruded Aluminum Grid (now available in steel as well) with factory applied gasketing are recommended for Class 5-8 clean room applications. PVC hold down clips are available but not required for clean room performance. Clean rooms Class 4 or less usually require 100% Hepa filter installations.
4. For a clean room application, do I need to seal my panels into the grid?
   We recommend a PVC hold down clip to insure a good seal but the hold down clip is not required for clean room performance ISO Class 5 or higher when using the Co-extruded Aluminum and Steel Clean Room grid system.

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1. Are Armstrong ceilings safe to install & use?
   Yes.
   • INSTALLATION. Studies have shown that exposures during conventional installation are below all current occupational standards for nuisance and other listed substances (dust). If power tools are used in the installation, they should be equipped with special dust collection devices, and the workers should wear the appropriate NIOSH-designated respirators.
   • IN-PLACE. Once installed, Armstrong ceiling products do not represent an identifiable health risk to the general building occupants.
2. Do Armstrong ceiling products contain mineral wool?  If so, do these products represent a health risk?
   Some Armstrong ceilings contain mineral wool, but they do not represent a health risk (see below).
   • PRODUCT. The safety of those Armstrong acoustical ceiling products that do contain mineral wool has been confirmed through occupational studies of mineral wool workers which have been carried out for more than 50 years. The results of these studies and reviews by independent researchers give no indication that exposure to products which contain mineral wool causes a health risk.
   • INSTALLATION. The installation practices for ceiling products recommended by Armstrong and other manufacturers have been monitored. Those studies which were submitted to United States Department of Labor, Occupational Safety & Health Administration ("OSHA") showed that exposure to mineral wool during the installation of the ceiling materials, when typical installation practices are used, are significantly below the permissible exposure limit (PEL) of one fiber per cubic centimeter for such materials.
   • IN-PLACE. Once installed, Armstrong ceiling products do not represent an identifiable health risk to the general building occupants.
3. Do Armstrong ceiling products contain silica?  If so, do these products represent a health risk?
   Armstrong mineral wool ceilings contain silica, but they do not represent a health risk (see below).
   • PRODUCT. Silica is present in most Armstrong mineral wool ceiling products. Tests conducted for Armstrong which monitored a typical installation did not detect the presence of any respirable silica.
   • INSTALLATION. Silica is present in most Armstrong mineral wool ceiling products. Tests conducted for Armstrong which monitored a typical installation of these products did not detect the presence of any respirable silica. The only foreseeable installation practice that may generate measurable levels of respirable silica would be through the use of power tools. For this reason, Armstrong and other manufacturers recommend that a dust respirator, as well as a dust collection device, be used during power tool applications.
   • IN-PLACE. Once installed, Armstrong ceiling products do not represent an identifiable health risk to the general building occupants.
4. Do Armstrong ceiling products release formaldehyde? If so, do they represent a health hazard?
   • PRODUCT. Certain materials used in the production of Armstrong ceiling products may result in the release of small amounts of formaldehyde at the time of installation. During the manufacturing process, the majority of the formaldehyde is driven off.
   • INSTALLATION. Studies have shown that any residual formaldehyde releases at the time of installation dissipate very quickly with adequate ventilation and are well below permissible exposure levels established by the United States Department of Labor, Occupational Safety & Health Administration (OSHA).
   • IN-PLACE. Installed Armstrong ceiling products do not represent an identifiable health risk to the general building occupants.
5. Do Armstrong fiberglass ceiling products represent a health hazard?
   • PRODUCT. The safety of Armstrong fiberglass ceiling products has been confirmed through occupational studies of fiberglass workers over the last 50 years. The results of these studies and reviews by independent researchers give no indications that exposure to products which contain fiberglass causes a health risk.
   • INSTALLATION. Studies have shown that exposures during conventional installation are below all current occupational standards for nuisance and other listed substances (dust). If power tools are used in the installation, they should be equipped with special dust collection devices, and the workers should wear the appropriate NIOSH-designated respirators. The only foreseeable health effect that may be caused by fiberglass is an irritation of the skin during the installation process. This condition is transient and disappears when physical contact ceases.
   • IN-PLACE. Installed Armstrong ceiling products do not represent an identifiable health risk to the general building occupants.
6. Has there been a recent favorable change in the ruling regarding the health aspects and classification of fibrous glass, mineral and slag wool?
   • PRODUCT. In October 2001, an expert review by the International Agency for Research on Cancer (IARC) re-evaluated the 1988 IARC assessment of fibrous glass, rock and slag wool fibers. This ruling removed them from the list of possible carcinogens by downgrading the classification of these fibers from Group 2B (possible carcinogen) to Group 3 (not classified as to carcinogenicity in humans). All Armstrong ceiling products that use these fibers are included in this classification.
7. Are respirable fibers released during general maintenance activities that would require the disturbance/removal of the OPTIMA High-NRC product?
   Tests* were conducted to measure respirable fibers generated following the installation, removal/reinstallation of the Hi-LR OPTIMA fiberglass product. In all cases, the results of the monitoring** one hour, and 24 hours, after each activity did not detect the presence of respirable airborne fiber.
   
   **Large chamber protocol followed the guidelines of ASTM Standard D5116. The dynamic chamber was operated at one air change per hour and 23×C and 50% relative humidity.
   **Fiber counts were conducted in accordance with NIOSH Method 7400B.
8. 8. Are respirable fibers released during general maintenance activities that would require the disturbance/removal of the CIRRUS product?
   Tests* were conducted to measure respirable fibers generated following the installation, removal/reinstallation of the CIRRUS mineral fiber product. In all cases, the results of the monitoring** one hour, and 24 hours, after each activity did not detect the presence of respirable airborne fibers.
   
   **Large chamber protocol followed the guidelines of ASTM Standard D5116. The dynamic chamber was operated at one air change per hour and 23×C and 50% relative humidity.
   **Fiber counts were conducted in accordance with NIOSH Method 7400B.

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1. How do I find replacement tiles?
   If your ceiling is damaged, water stained, or discolored, consider replacing the damaged ceiling product. Visit our replacement ceilings page to get started. In just a few clicks you'll be on your way to a brand new ceiling.
2. How do you clean and disinfect Armstrong ceilings?
   Due to differences in the finishes and textures of our various ceiling, wall and suspension systems products, each product or product family requires a different method of cleaning.

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