Fire-resistance rating

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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 a host of other criteria, involving other evidence of functionality or fitness for purpose.

Contents

Common rating systems

The following depict the most commonly used international time/temperature curves:

International fire-resistance ratings

There are many international variations for nearly countless types of products and systems, some with multiple test requirements.

Canada's Institute for Research in Construction (a part of the National Research Council and publisher of Canada's model building code - NBC) requires a special test regime for firestops for plastic pipe penetrants. Fire endurance tests for this application must be run under 50Pa positive furnace pressure in order to adequately simulate the effect of potential temperature differences between indoor and outdoor temperatures in Canada's winters. Special hoods are applied here to provide suction on the top side of a test assembly in order to reach the 50Pa pressure differential. Afterwards, a 30PSI hose-stream test may be applied.

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.

If critical environmental conditions are not satisfied, an assembly may not be eligible for a fire-resistance rating.

Regardless of the complexity of any given test regime that may lead to a rating, the premise is generally product certification and, most importantly listing and approval use and compliance. Testing without certification and installations that cannot be matched with an appropriate certification listing, are not usually recognised by any Authority Having Jurisdiction (AHJ) unless it is in a realm where product certification is optional.

Tests for fire resistance of record protection equipment

The following classifications may be attained when testing in accordance with UL 72. [1]

Class 125 Rating

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.

Class 150 Rating

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.

Class 350 Rating

This rating is the requirement for protecting paper documents. Above 350 °F (176.7 °C) paper is distorted by the heat and information is lost. A Class 350-4 Hour vault must keep the temperature below 350 °F. for at least four hours, with temperatures up to 2,000 °F. (1,093.3 °C) outside the vault.

Different time/temperature curves

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 & 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.

Big differences between different countries in terms of the use of the curves include the use of pipes, which shield the furnace thermocouples inside of NAFTA testing laboratories. This slows down the response time and results in a somewhat more conservative test regime in North America. On the other hand, the ISO based European curves run somewhat hotter for most of the test. North America also selectively uses a hose-stream test between 30 and 45PSI, to simulate real-world impacts and damages that may not be simulated in a laboratory. The US Navy even insists on a 90PSI hose-stream test for some of its assemblies, which may simulate the pressure available to firefighters in fighting a fire, but which has little to do with countermeasures against damaging effects of manual fire suppression. The hose-stream is simply intended to add a level of toughness to matters because without this, some fairly flimsy systems can pass a test, thus receive a rating and thus be permissible by a building code but be so weak that ordinary building use may damage a thus qualified system before it encounters a fire.

Germany's DIN4102 also includes a significant impact test for a potential firewall, which is, however, applied from the wrong side: the cold side. Applying the impact from the cold side is more practical to do in a lab setting, however, potential impacts should come from the exposed side, not the unexposed side. Still, for the person designing, building and paying for the test, the fire resistance itself may be rather uneventful unless major problems appear. The burn itself is the long duration, up to 4 hours, but the hose stream test only lasts a few minutes, with large damage potential due to the sudden thermal and kinetic impacts, as the fire was upwards of 1,100 °C (see curves above), whereas the sudden hose-stream test is as cold as the domestic water fed to the fire hose used in the test, which might be 10-20 °C. This combined impact explains the debris that can be seen coming from test specimens during the hose stream test, as seen herein.

Because of the large differences in test regimes all over the world, even for identical products and systems, organizations that intend to market their products internationally are often required to run many tests in many countries. Even where test regimes are identical, countries are often reluctant to accept the test results and particularly the certification methods of other countries.

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 the environment inside a "tube" is best described as a "microclimate". The heat cannot escape as well as it can in a burning refinery, which is in the open. 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. This scenario was tested and quantified, particularly during the "Eureka Project", run by Technische Universität Braunschweig's iBMB, Ekkehard Richter. The Netherlands, through Rijkswaterstaat in particular, mandated an extremely tough standard, the curve of which is shown in the gallery above.

Example of a fire stop fire-resistance rating test

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.

Ulc nachher alles dicht.jpg

Part B: The Burning Branding Test. This test consists of mock decks being subject the placement of a burning brand in the center of the mock deck to simulate the falling of burning embers during a wildfire. The deck must be absent of flame after the 40 minute test period and lack structural failure of any boards.

TimberSIL wood Burning Brand Test 0:00:00 Buring-brand-fire-Test.jpg
TimberSIL wood Burning Brand Test 0:00:00
TimberSIL wood Burning Brand Test after 0:40:09 Buring-brand-fire-Test-0-40-09.jpg
TimberSIL wood Burning Brand Test after 0:40:09

See also

Related Research Articles

Firewall (construction)

A firewall is a fire-resistant barrier used to prevent the spread of fire. Firewalls are built between or through buildings, structures, or electrical substation transformers, or within an aircraft or vehicle.

Ceiling

A ceiling is an overhead interior surface that covers the upper limits of a room. It is not generally considered a structural element, but a finished surface concealing the underside of the roof structure or the floor of a story above. Ceilings can be decorated to taste, and there are many fine examples of frescoes and artwork on ceilings especially in religious buildings. A ceiling can also be the upper limit of a tunnel.

Fire door

A fire door is a door with a fire-resistance rating used as part of a passive fire protection system to reduce the spread of fire and smoke between separate compartments of a structure and to enable safe egress from a building or structure or ship. In North American building codes, it, along with fire dampers, is often referred to as a closure, which can be derated compared against the fire separation that contains it, provided that this barrier is not a firewall or an occupancy separation. In Europe national standards for fire doors have been harmonised with the introduction of the new standard EN 16034, which refers to fire doors as fire-resisting door sets. Starting September 2016, a common CE marking procedure was available abolishing trade barriers within the European Union for these types of products. In the UK, it is Part B of the Building Regulations that sets out the minimum requirements for the fire protection that must be implemented in all dwellings this includes the use of fire doors. All fire doors must be installed with the appropriate fire resistant fittings, such as the frame and door hardware, for it to fully comply with any fire regulations.

Fireproofing

Fireproofing is rendering something resistant to fire, or incombustible; or material for use in making anything fire-proof. It is a passive fire protection measure. "Fireproof" or "fireproofing" can be used as a noun, verb or adjective; it may be hyphenated ("fire-proof").

An intumescent is a substance that swells as a result of heat exposure, thus leading to an increase in volume and decrease in density. Intumescents are typically used in passive fire protection and require listing, approval, and compliance in their installed configurations in order to comply with the national building codes and laws.

Fire protection

Fire protection is the study and practice of mitigating the unwanted effects of potentially destructive fires. It involves the study of the behaviour, compartmentalisation, suppression and investigation of fire and its related emergencies, as well as the research and development, production, testing and application of mitigating systems. In structures, be they land-based, offshore or even ships, the owners and operators are responsible to maintain their facilities in accordance with a design-basis that is rooted in laws, including the local building code and fire code, which are enforced by the Authority Having Jurisdiction.

A firestop or fire-stopping is a form of passive fire protection that is used to seal around openings and between joints in a fire-resistance-rated wall or floor assembly. Firestops are designed to maintain the fireproofing of a wall or floor assembly allowing it to impede the spread of fire and smoke.

Passive fire protection

Passive fire protection (PFP) is an integral component of the components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, such as by fire-resistant walls, floors, and doors. PFP systems must comply with the associated listing and approval use and compliance in order to provide the effectiveness expected by building codes.

Firestop pillow

Firestop pillows are passive fire protection items, used for firestopping holes in wall or floor assemblies required to have a fire-resistance rating. The products must be used in accordance with a valid certification listing, subject to listing and approval use and compliance.

Within the context of building construction and building codes, "occupancy" refers to the use, or intended use, of a building, or portion of a building, for the shelter or support of persons, animals or property. A closely related meaning is the number of units in such a building that are rented, leased, or otherwise in use. Lack of occupancy, in this sense, is known as "vacancy".

Circuit integrity

Circuit integrity refers to the operability of electrical circuits during a fire. It is a form of fire-resistance rating. Circuit integrity is achieved via passive fire protection means, which are subject to stringent listing and approval use and compliance.

Fire test

A fire test is a means of determining whether fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation. Successful tests in laboratories holding national accreditation for testing and certification result in the issuance of a certification listing. The listing is public domain, whereas the test report itself is proprietary information belonging to the test sponsor.

Pressurisation ductwork

Pressurisation duct work is a passive fire protection system. It is used to supply fresh air to any area of refuge, designated emergency evacuation or egress route.

Annulus (firestop) the space between a penetrant and whatever surrounds it

The annulus, or annular space, is the space between a penetrant and whatever surrounds it, such as the sides of an opening or a sleeve, as the case may be.

Combustibility and flammability Ability to easily ignite in air at ambient temperatures

A combustible material is something that can combust (burn) in air. Flammable materials are combustible materials that ignite easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame.

Grease duct

A grease duct is a duct that is specifically designed to vent grease-laden flammable vapors from commercial cooking equipment such as stoves, deep fryers, and woks to the outside of a building or mobile food preparation trailer. Grease ducts are regulated both in terms of their construction and maintenance, forming part of the building's passive fire protection system. The cleaning schedule is typically dictated by fire code or related safety regulations, and evidence of compliance must be kept on file by the owner.

A building joint is a junction where building elements meet without applying a static load from one element to another. When one or more of these vertical or horizontal elements that meet are required by the local building code to have a fire-resistance rating, the resulting opening that makes up the joint must be firestopped in order to restore the required compartmentalisation.

A certification listing is a document used to guide installations of certified products, against which a field installation is compared to make sure that it complies with a regulation. Typically, products or items are required to be installed or used in accordance with a subject-related certification listing if those products or items are subject to product certification and must be used in a specific manner in order to be safe for use. Certification listings are issued by organisations that are usually nationally accredited for doing both testing and product certification work, in accordance with nationally accredited standards.

Fire damper

Fire dampers are passive fire protection products used in heating, ventilation, and air conditioning (HVAC) ducts to prevent the spread of fire inside the ductwork through fire-resistance rated walls and floors. Fire/smoke dampers are similar to fire dampers in fire resistance rating, and also prevent the spread of smoke inside the ducts. When a rise in temperature occurs, the fire damper closes, usually activated by a thermal element which melts at temperatures higher than ambient but low enough to indicate the presence of a fire, allowing springs to close the damper blades. Fire dampers can also close following receipt of an electrical signal from a fire alarm system utilising detectors remote from the damper, indicating the sensing of heat or smoke in the building occupied spaces or in the HVAC duct system.

EN 16034 refers to a set of European standards which specify the technical performance characteristics for fire resisting and/or smoke control products, or better known in common language as fire/smoke doors or fire/smoke proof doors. Compliance with this standard requires to fulfill the requirements of the Construction Product Regulation for construction products, which are placed on the EU market with the intention to become permanent parts of a construction.

References

  1. "Standard 72 - Standard for Tests for Fire Resistance of Record Protect". ulstandards.ul.com. Retrieved 2016-09-21.