J60 Fire Rating Definition
Gene Honnette
A fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test. This can be quantified simply as a measure of time, or it may entail other criteria, involving evidence of functionality or fitness for purpose.
Outdoor spray fireproofing methods that must be qualified to the hydrocarbon curve may be required to pass a host of environmental tests before any burn takes place, to minimize the likelihood of ordinary operational environments rendering a vital system component useless before it ever encounters a fire.
This rating is the requirement in data safes and vault structures for protecting digital information on magnetic media or hard drives. Temperatures inside the protected chamber must be held below 125 F (52 C) for the time period specified, such as Class 125-2 Hour, with temperatures up to 2,000 F (1,090 C) outside the vault. The temperature reading is taken on the inside surfaces of the protective structure. Maintaining the temperature below 125 F is critical because data is lost above that temperature threshold, even if the media or hard drives appear to be intact.
This is the rating required to protect microfilm, microfiche, and other film-based information storage media. Above 150 F (65.5 C) film is distorted by the heat and information is lost. A Class 150-2 Hour vault must keep the temperature below 150 F. for at least two hours, with temperatures up to 2,000 F. (1,093.3 C) outside the vault.
Typically, most countries use the building elements curve for residential and commercial spaces, which is nearly identical in most countries as that is what results by burning wood. The building elements curve is characterized jointly by, including, but not limited to, DIN4102, BS476, ASTM E119, ULC-S101, etc. For industrial facilities in the hydrocarbon and petrochemical industries, a hydrocarbon curve (such as UL 1709) is used, reflecting a more rapid temperature rise. The only commonly used exposure beyond this, apart from the more recent tunnel curves shown above, would be the jet fire exposure standards such as ISO 22899, which are used where equipment may be subject to the extreme heat and momentum effects of jet fire exposure.
During a fire in a tunnel, as well as in the petrochemical industry, temperatures exceed those of ordinary building (cellulosic) fires. This is because the fuel for the fire is hydrocarbons, which burn hotter (compare hydrocarbon curve above to ASTM E119 curve), faster and typically run out of fuel faster as well, compared against timber. The added complication with tunnels is that heat cannot escape as well as it can in open area. Instead, the fire is confined to a narrow tube, where pressure and heat build up and spread rapidly, with little room for escape and little chance of compartmentalization.
Construction of a test sample consists of a mockup of a section of concrete floor, with typical mechanical and electrical utility components (pipes and cables) penetrating the floor assembly. A firestop mortar is applied around the penetrations.
The completed test sample is inserted into a furnace such that one side is exposed to a fire. The test is terminated when the fire stops successfully meet the test criteria in minimizing the amount of heat and smoke allowed to pass through the assembly, when the fire penetrates the fire stops. This determines the fire stop F-Rating. The length of time required for a penetrant or sample on average to exceed a specified average heat rise above ambient at any single location determines the duration for the FT Rating (Fire and Temperature). If a hose-stream test is passed afterwards, the rating can then be expressed as an FTH Rating (Fire, Temperature and Hose-stream). The lowest of the three determines the overall rating.
The ASTM E-84 tests characteristics of flame and smoke of a material. The ASTM E-119 measures the fire resistance of a structure. With the right covering, your project can exceed the requirements for both tests.
The ASTM E-84 is based on two main metrics of burning behavior. These metrics are flame spread and smoke development. The flame spread index is a measure of how quickly the flame travels after the fire is initiated. The smoke development rating tells you how much smoke is produced over a period of time.
Flame spread index and smoke development are tested in the Steiner Tunnel, a 24 x 24-inch steel box. A sample of the material is exposed to two burners. Then, the sample is monitored through a window. The flame spread and smoke development are analyzed with specialized software.
Class A (or Class 1) is the best fire rating. The flame spread for a Class A fire rating is 25 or lower, and the smoke development does not exceed a maximum of 450. Many facilities require a Class A rating for building materials. For example, hospitals typically require Class A ratings.
To perform the ASTM E-119 test, a sample of a material is placed in a furnace. The material is left in the furnace for a pre-specified amount of time and temperature. At the end of the test, the material is checked for its structural integrity.
Different materials have higher and lower flame spread rating. The chart below compiles information from various sources and shows flame-spread ratings for some common building materials according to the Louisiana Fire Marshal website:
A 1-hour fire rated wall is able to remain intact after one hour of being exposed to fire. For example, the fire would not penetrate the structure after an hour. If your project keeps its integrity for at least one hour of burning, it would receive a 1-hour rating. Most facilities require a minimum of a 1-hour fire rating.
Some walls are built with materials that come guaranteed with a 1-hour fire rating. For example, the Intertek Design LPB/WPPS-60-01 wall is constructed with gypsum. It is designed to receive 1-hour fire ratings for both sides of the assembly.
Different classifications refer to different levels of flammability and smoke production. Understanding the fire-resistance rating of materials gives you the knowledge you need to make effective choices.
Flame spread index is a numerical value that is typically obtained by examining how the material responds during a ten-minute tunnel test. The flame spread index value is expressed as an arbitrary numerical value, where the asbestos-cement board has a rating of zero, and red oak has a value of one hundred.
Each of the fire rating classifications has a flame spread index range assigned to it. Having a basic understanding of the fire-resistance rating of structural elements is invaluable in protecting property against fire. These are the classes recognized by the National Fire Protection Association Life Safety Code, NFPA No. 101.
Materials that fall into Class A or Class 1 include things like brick, gypsum wallboard, and fiber cement exterior materials. These materials do not burn well and are very unlikely to contribute fuel to a fire.
A whole wood material would be wood planks that are in the same form as they were when they were cut from the tree. They burn more quickly than Class A materials and more slowly than Class C materials.
A Class C or Class 3 fire rating has a flame spread rating between 76 and 200. This rating incorporates building materials like plywood, fiberboard, and hardboard siding panels. It also includes any of the faster burning whole woods.
Ratings between 201 and 500 would be considered a Class D material, and Class E materials include anything with a flame spread rating above 500. Classes D and E are not considered effective against any form of fire exposure.
Knowing how your building materials will hold up against fire is a great first step toward effective protection. Choosing materials with higher fire rating classifications may be the barrier that saves your home from a fire.
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Fire doors are rated in terms of minutes/hours; the fire rating defines how long the assembly was tested to withstand a fire. Some common fire door ratings are 20, 45, 60, 90, and 180 (minutes). The fire rating required depends on the adopted building codes and the location of the door opening. Fire doors are typically rated less than the wall itself (ex. a 4-hour wall gets a 3-hour door assembly) since the door does not carry a fuel load such as artwork, adjacent furniture, etc.
Fire rated doors and frames are available in many types including wood, hollow metal, and specialty products such as FRP (Fiber Reinforced Polymer). Some door types, such as wood doors, also require intumescent seals either built into the door edge or supplied as a separate item that attaches to the fire door frame.
Fire doors are required in certain wall types as dictated by local, state, national, and international building codes (ex. IBC, NFPA 101). You can typically find fire rated doors in fire walls, fire barriers, fire partitions, and smoke barrier walls. Building codes outline the mandated fire resistance rating of the fire door assembly based on the type of space and occupancy. All fire door assemblies must be tested using the appropriate standard and installed according to NFPA 80.
Fire-rated assemblies constructed with gypsum board or drywall are a key component to ensuring life safety and complying with applicable building codes in both residential and commercial construction. The gypsum board used in fire-rated assemblies is usually described as either Type X or Type C. As a result, understanding the differences between these terms will aid in the selection of the correct product for use in each specific fire-rated assembly.
National Gypsum Company, through its affiliate company Gold Bond Building Products, LLC, provides more than two dozen Type X and Type C drywall products to meet a variety of requirements in addition to fire ratings, such as resistance to mold, moisture, sound, abuse, impact and weather exposure.
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