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The Problem With Leakage Ratings

More and more UL Firestop Sysems for cable penetrations now carry L-Ratings. Do you know what they mean? It seems simple doesn’t it? Air is pumped into a chamber and the rate at which it leaks out is measured. Pretty simple… Or is it? It would be if that’s all there was to it. Unfortunately there’s more to it than this. Unless you understand what you are reading, you may be mislead. The purpose of this Technical Update is to tell you how this published value is determined and just what it means.

While some of you may have actually witnessed a fire test at UL or elsewhere, I would be very surprised if any potential readers have witnessed the UL leakage testing. To get you prepared for this discussion, I’ll give you the benefit of our experience.

The requirements for leakage testing are found in UL/ANSI 1479. Since this requirement is not as yet included in ASTM E814, we will focus on the the requirements of the UL standard.

Leakage occurs within the cable bundle and not around it. Consider the typical cable installation depicted in a UL Through-Penetration System. The cable bundle is centered and the seal (be it putty, sealant, or foam muffins) is installed around it. These materials are not typically porous. This means that if there is leakage occurring, the air is flowing between the cables
rather than around them.

Some UL Systems with cables do have very low values that are legitimate. Firestop products or designs that seal around each individual cable will produce low leakage ratings. In areas where a hermetic seal is required, for example marine applications where penetrations occur in bulkheads, complex rubber block systems are installed and compressed tightly around each pipe and cable. This level of sealing may also be required for certain clean areas or pressurized areas within electronics manufacturing plants for example.

Other UL Systems indicate low values that are not! For most forms of normal construction however, it isn’t practical to attempt to seal cables air-tight. Achieving low values with cable bundles using sealants, putties, foam plugs, etc. require cables to be individually spaced and sealed so that air will not flow between them.

Published L Ratings – Be Sure to Read the Small Print! Don’t be fooled by low numbers. Extremely low numbers for cables usually mean that each cable has been individually sealed. Is this practical? Some pathway devices with self-contained firestopping require putty to be packed in both ends in order to achieve the rating. Be sure to read the small print.

These systems may also have cable bundles that are tightly cinched the cables are squeezed together with as little room between them as possible.

Since this is not practical in actual practice, these ratings simply are not realistic and the published values are not truly representative of what the average installer can reproduce in the field.

The bigger problem is how the actual test results are interpolated under UL1479. Looking at a UL System, you would naturally expect that if you install a single penetration using the parameters shown, you will get X leakage. You would also assume that if you install three of these penetrations, you will get 3X leakage. Unfortunately unless the actual tested opening size is exactly one square foot, you will not actually know the true leakage.

UL1479 adjusts the actual value achieved in the test up or down by dividing the Actual Leakage by the square footage of the opening (See Fig. 2). This can produce some very surprising results. If the opening is smaller than one square foot, the leakage value will be increased. If the opening is larger than one square foot, it will decrease. It doesn’t make much sense, but if you install either one of the penetrations shown in Fig. 2, your actual leakage will be the same. However, the larger opening may meet code requirements and the smaller one will not.

What does “less than 1” really mean? UL1479 does not provide for a rating of zero (0). The lowest rating is “Less than 1”. Since this is the lowest possible rating, this would seem to be as good as it gets. However, consider an opening 5’ X 5’ (25 ft2) with no cables or penetrants of any kind. In theory, we could seal this opening with an impermeable membrane such as a metal-backed composite firestop sheet and caulk the edges so that there would be absolutely no leakage. However, using UL1479, the lowest rating that could be assigned would be “less than 1” rather than “0”.

Now let’s assume that we have created an opening in this firestop membrane and installed and firestopped a cable bundle. We re-test and subsequently measure leakage of 24 ft3 per minute, our interpolated leakage would be 24 ÷ 25 = .96 or “less than 1” once again. So even though we have no leakage in our first example and 24 ft3 in the second, anyone reading the two systems would never know the difference.

This standard and the codes need to be changed. Until then, be careful about the products and systems that you select. Don’t be afraid to call the manufacturer and request the Actual Leakage values. This is the only accurate measure of leakage.

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 Data Sheets

Penetrations

  1. Caulks, Sealants & Putties
    Product
    Product Data Sheet
    Safety Data Sheet
    SSS Intumescent Sealant
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    LCI Intumescent Sealant
    pdf_icon_small
    pdf_icon_small
    SIL Silicone Sealant (Non-Sag)
    pdf_icon_small
    pdf_icon_small
    SIL Silicone Sealant (Self-Leveling)
    pdf_icon_small
    pdf_icon_small
    PEN200 Silicone Foam
    pdf_icon_small
    pdf_icon_small
    WF Caulk
    pdf_icon_small
    pdf_icon_small
    LC Endothermic Sealant
    pdf_icon_small
    pdf_icon_small
    SSP Putty
    pdf_icon_small
    pdf_icon_small
    SSP Putty Pads
    pdf_icon_small
    pdf_icon_small


  1. Collars, Wrap Strip & Cast-In
    Product
    Product Data Sheet
    Safety Data Sheet
    CID Cast-In Firestop Device
    pdf_icon_small
    pdf_icon_small
    SSC Intumescent Firestop Collars
    pdf_icon_small
    pdf_icon_small
    LCC Intumescent Firestop Collars
    pdf_icon_small
    pdf_icon_small
    RTC Intumescent Firestop Collars
    pdf_icon_small
    pdf_icon_small
    BLU Wrap Strip
    pdf_icon_small
    pdf_icon_small
    BLU2 Wrap Strip
    pdf_icon_small
    pdf_icon_small
    BLU220, BLU230, BLU240 Wrap Strip
    pdf_icon_small
    pdf_icon_small
    RED Wrap Strip
    pdf_icon_small
    pdf_icon_small
    RED2 Wrap Strip
    pdf_icon_small
    pdf_icon_small
    SSW125, SSW250, SSW375 Wrap Strip
    pdf_icon_small
    pdf_icon_small


  1. EZ-Path Fire-Rated Pathways
    Product
    Product Data Sheet
    Safety Data Sheet
    EZ-Path 44+
    pdf_icon_small
    pdf_icon_small
    EZ-Path 33
    pdf_icon_small
    pdf_icon_small
    EZ-Path 22
    pdf_icon_small
    pdf_icon_small
    EZ-Path Retrofit Device
    pdf_icon_small
    pdf_icon_small
    EZ Firestop Grommet
    pdf_icon_small
    pdf_icon_small


  1. Electrical & DataCom Cabling
    Product
    Product Data Sheet
    Safety Data Sheet
    EZ-Path 44+
    pdf_icon_small
    pdf_icon_small
    EZ-Path 33
    pdf_icon_small
    pdf_icon_small
    EZ-Path 22
    pdf_icon_small
    pdf_icon_small
    EZ-Path Retrofit Device
    pdf_icon_small
    pdf_icon_small
    EZ Firestop Grommet
    pdf_icon_small
    pdf_icon_small
    SSS Intumescent Firestop Sealant
    pdf_icon_small
    pdf_icon_small
    LCI Intumescent Firestop Sealant
    pdf_icon_small
    pdf_icon_small
    SSB Intumescent Firestop Pillows
    pdf_icon_small
    pdf_icon_small
    Composite Sheet
    pdf_icon_small
    pdf_icon_small
    SSM Firestop Mortar
    pdf_icon_small
    pdf_icon_small
    Electrical Box Insert
    pdf_icon_small
    pdf_icon_small
    SSP Putty
    pdf_icon_small
    pdf_icon_small
    SSP Putty Pads
    pdf_icon_small
    pdf_icon_small
    FP Intumescent Firestop Plug
    pdf_icon_small
    pdf_icon_small
    Ready® Sleeve
    pdf_icon_small
    pdf_icon_small
    Ready® Split Sleeve
    pdf_icon_small
    pdf_icon_small
    EZ-Path® Series 33NEZ Smoke and Acoustical Device (Wall – Blue)
    pdf_icon_small
    pdf_icon_small
    EZ-Path® Series 33NEZ Smoke and Acoustical Device (Wall – White)
    pdf_icon_small
    EZ-Path® Series 33NEZ Smoke and Acoustical Device (Ceiling)
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    pdf_icon_small
    EZ-Path® Series 44NEZ Smoke and Acoustical Device
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    pdf_icon_small


  1. Electrical Circuit Protection
    Product
    Product Data Sheet
    Safety Data Sheet
    Cable Spray
    pdf_icon_small
    pdf_icon_small
    E-Wrap™
    pdf_icon_small
    pdf_icon_small
    Thermal Barrier Wrap
    pdf_icon_small
    pdf_icon_small


  1. Outlet & Panel Box Protection
    Product
    Product Data Sheet
    Safety Data Sheet
    Electrical Box Insert
    pdf_icon_small
    pdf_icon_small
    SSP Putty
    pdf_icon_small
    pdf_icon_small
    SSP Putty Pads
    pdf_icon_small
    pdf_icon_small
    Thermal Barrier Wrap
    pdf_icon_small
    pdf_icon_small


  1. Large Opening
    Product
    Product Data Sheet
    Safety Data Sheet
    SSB Intumescent Firestop Pillows
    pdf_icon_small
    pdf_icon_small
    Composite Sheet
    pdf_icon_small
    pdf_icon_small
    SSM Firestop Mortar
    pdf_icon_small
    pdf_icon_small


  1. Packing/Forming Materials
    Product
    Product Data Sheet
    Safety Data Sheet
    STI-SSAMW
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    IIG (JM)-Type CW8
    pdf_icon_small
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    IIG (JM)-Minwool 1200 Safing
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Firespan 40 & 90
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Impasse System Complete
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Impasse System Hangers
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Impasse System Spiral Anchors
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Safing
    pdf_icon_small
    pdf_icon_small
    ROCKWOOL-CurtainRock 40
    pdf_icon_small
    pdf_icon_small
    ROCKWOOL-CurtainRock 80
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    pdf_icon_small
    Roxul-Safe
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  1. Other
    Product
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    Safety Data Sheet
    FyreFlange HVAC Firestop Angle
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    Closet Flange Firestop Gasket
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Construction Joints

  1. Joint Sprays
    Product
    Product Data Sheet
    Safety Data Sheet
    AS200 Elastomeric Spray
    pdf_icon_small
    pdf_icon_small
    Fast Tack® Firestop Spray
    pdf_icon_small
    pdf_icon_small


  1. Joint Sealants
    Product
    Product Data Sheet
    Safety Data Sheet
    SSS Intumescent Firestop Sealant
    pdf_icon_small
    pdf_icon_small
    LCI Intumescent Firestop Sealant
    pdf_icon_small
    pdf_icon_small
    SIL Silicone Sealant (Non-Sag)
    pdf_icon_small
    pdf_icon_small
    SIL Silicone Sealant (Self-Leveling)
    pdf_icon_small
    pdf_icon_small
    ES Elastomeric Firestop Sealant
    pdf_icon_small
    pdf_icon_small
    LC Endothermic Firestop Sealant
    pdf_icon_small
    pdf_icon_small


  1. SpeedFlex Joint Protection
    Product
    Product Data Sheet
    Safety Data Sheet
    SpeedFlex® TTG Track Top Gasket
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    pdf_icon_small
    SpeedFlex® Joint Profile System
    pdf_icon_small
    pdf_icon_small

Curtain Wall

  1. Perimeter Fire Barrier Sprays
    Product
    Product Data Sheet
    Safety Data Sheet
    AS200 Elastomeric Spray
    pdf_icon_small
    pdf_icon_small
    Fast Tack® Firestop Spray
    pdf_icon_small
    pdf_icon_small
    Safing Spray
    pdf_icon_small
    pdf_icon_small


  1. All Weather Firestop Sprays
    Product
    Product Data Sheet
    Safety Data Sheet
    Fast Tack® Firestop Spray
    pdf_icon_small
    pdf_icon_small


  1. Anchor Protection
    Product
    Product Data Sheet
    Safety Data Sheet
    Connection Protection
    pdf_icon_small
    pdf_icon_small


  1. Curtain Wall Insulation Materials
    Product
    Product Data Sheet
    Safety Data Sheet
    STI-SSAMW
    pdf_icon_small
    pdf_icon_small
    IIG (JM)-Type CW8
    pdf_icon_small
    pdf_icon_small
    IIG (JM)-Minwool 1200 Safing
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Firespan 40 & 90
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Impasse System Complete
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Impasse System Hangers
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Impasse System Spiral Anchors
    pdf_icon_small
    pdf_icon_small
    Owens Corning Thermafiber-Safing
    pdf_icon_small
    pdf_icon_small
    ROCKWOOL-CurtainRock 40
    pdf_icon_small
    pdf_icon_small
    ROCKWOOL-CurtainRock 80
    pdf_icon_small
    pdf_icon_small
    Roxul-Safe
    pdf_icon_small
    pdf_icon_small


  1. Quick Clip Insulation Hangers
    Product
    Product Data Sheet
    Safety Data Sheet
    Quick Clip™
    pdf_icon_small
    pdf_icon_small
    Quick Clip™ L-Bracket
    pdf_icon_small
    pdf_icon_small

Smoke & Acoustical

  1. EZ-Path Smoke & Acoustical Pathway
    Product
    Product Data Sheet
    Safety Data Sheet
    EZ-Path® Series 33NEZ Smoke and Acoustical Device
    pdf_icon_small
    pdf_icon_small
    EZ-Path® Series 33NEZ Smoke and Acoustical Device (Ceiling)
    pdf_icon_small
    pdf_icon_small
    EZ-Path® Series 44NEZ Smoke and Acoustical Device
    pdf_icon_small
    pdf_icon_small


  1. Sealants & Sprays
    Product
    Product Data Sheet
    Safety Data Sheet
    Application Data Sheet
    Smoke N Sound Acoustical Spray
    pdf_icon_small
    pdf_icon_small
    pdf_icon_small
    Smoke N Sound Acoustical Sealant
    pdf_icon_small
    pdf_icon_small
    pdf_icon_small

Fireblocking/Draftstopping

  1. SmokeBlock
    Product
    Product Data Sheet
    Safety Data Sheet
    SmokeBlock® 136
    pdf_icon_small
    pdf_icon_small
    SmokeBlock® 200
    pdf_icon_small
    pdf_icon_small

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