Passive fire protection

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Fire-resistance rated wall assembly with fire door, cable tray penetration and intumescent cable coating Mortar intumescent.jpg
Fire-resistance rated wall assembly with fire door, cable tray penetration and intumescent cable coating

Passive fire protection (PFP) is components or systems of a building or structure that slows or impedes the spread of the effects of fire or smoke without system activation, and usually without movement. [1] Examples of passive systems include floor-ceilings and roofs, fire doors, windows, and wall assemblies, fire-resistant coatings, and other fire and smoke control assemblies. Passive fire protection systems can include active components such as fire dampers.

Contents

Main characteristics

Passive fire protection systems are intended to:

PFP systems are designed to "prevent" the spread of fire and smoke, or heating of structural members, for an intended limited period of time as determined by the local building code and fire codes. Passive fire protection measures such as firestops, fire walls, and fire doors, are tested to determine the fire-resistance rating of the final assembly, which is usually expressed in terms of hours of fire resistance (e.g., ⅓, ¾, 1, 1½, 2, 3, 4 hour). A certification listing provides the limitations of the rating.

Passive fire protection systems typically do not require motion. Exceptions are fire dampers (fire-resistive closures within air ducts, excluding grease ducts) and fire door closers, which move, open and shut in order to work, as well as all intumescent products which swell in order to provide adequate material thickness and fill gaps. The simplicity of PFP systems usually results in higher reliability as compared to active fire protection systems such as sprinkler systems which require several operational components for proper functioning.

PFP in a building perform as a group of systems within systems. For example, an installed firestop system is part of a fire-resistance rated wall system or floor system, which is in turn a part of a fire compartment which forms an integral part of the overall building which operates as a system.

Different types of materials are employed in the design and construction of PFP systems. Endothermic materials absorb heat, including calcium silicate board, concrete and gypsum wallboard. For example, water can boil out of a concrete slab when heated. The chemically bound water inside these materials sublimates when heated. PFP measures also include intumescents and ablative materials. Materials themselves are not fire resistance rated. They must be organised into systems which bear a fire resistance rating when installed in accordance with certification listings (e.g., DIN 4102 Part 4).

There are mainly two types of materials that provide structural fire resistance: intumescent and vermiculite. Vermiculite materials cover the structural steel members in a relatively thick layer. Because of the porous nature of vermiculite, its use is not advisable if there is the possibility of water exposure. Steel corrosion is also difficult to monitor. Intumescent fireproofing is a layer of a material which is applied like paint on the structural steel members. The thickness of this intumescent coating is dependent on the steel section used. Intumescent coatings are applied in a relatively low thickness (usually 350- to 700-micrometer), have a more aesthetic smooth finish, and help prevent corrosion.

PFP system performance is typically demonstrated in fire tests. A typical test objective for fire rated assemblies is to maintain the item or the side to be protected at or below either 140 °C (for walls, floors and electrical circuits required to have a fire-resistance rating). A typical test objective (e.g., ASTM E119) for fire rated structural protection is to limit the temperature of the structural element (e.g., beam, column) to ca. 538 °C, at which point the yield strength of the structural element has been sufficiently reduced that structural building collapse may occur. Typical test standards for walls and floors are BS 476: Part 22: 1987, BS EN 1364-1: 1999 & BS EN 1364-2: 1999 or ASTM E119. [2] Smaller components such as fire dampers, fire doors, etc., follow suit in the main intentions of the basic standard for walls and floors. Fire testing involves live fire exposures upwards of 1100 °C, depending on the fire-resistance rating and duration one is after. Test objectives other than fire exposures are sometimes included such as hose stream impact to determine the survivability of the system under realistic conditions.

Examples

This I beam has a fireproofing material sprayed onto it as a form of passive fire protection. Spray fireproofing on an ibeam.jpg
This I beam has a fireproofing material sprayed onto it as a form of passive fire protection.

Regulations

Examples of testing that underlies certification listing:

Each of these test procedures have very similar fire endurance regimes and heat transfer limitations. Differences include the hose-stream tests, which are unique to Canada and the United States, whereas Germany includes an impact test during the fire for firewalls. Germany is unique in including heat induced expansion and collapse of ferrous cable trays into account for firestops resulting in the favouring of firestop mortars which tend to hold the penetrating cable tray in place, whereas firestops made of rockwool and elastomeric toppings have been demonstrated in testing by Otto Graf institute to be torn open and rendered inoperable when the cable tray expands, pushes in and then collapses. [3]

In exterior applications for the offshore and the petroleum sectors, the fire endurance testing uses a higher temperature and faster heat rise, whereas in interior applications such as office buildings, factories and residential, the fire endurance is based upon experiences gained from burning wood. The interior fire time/temperature curve is referred to as "ETK" (Einheitstemperaturzeitkurve = standard time/temperature curve) [4] or the "building elements" curve, whereas the high temperature variety is called the hydrocarbon curve as it is based on burning oil and gas products, which burn hotter and faster. The most severe fire exposure test is the British "jetfire" test, [5] which has been used to some extent in the UK and Norway but is not typically found in common regulations.

Typically, during the construction of buildings, fire protective systems must conform to the requirements of building code that was in effect on the day that the building permit was applied for. [6] Enforcement for compliance with building codes is typically the responsibility of municipal building departments. [7] Once construction is complete, the building must maintain its design basis by remaining in compliance with the current fire code, which is enforced by the fire prevention officers of the municipal fire department. [8] An up-to-date fire protection plan, [9] containing a complete inventory and maintenance details of all fire protection components, including firestops, fireproofing, fire sprinklers, fire detectors, fire alarm systems, fire extinguishers, etc. are sometimes a requirement for demonstration of compliance with applicable laws and regulations.

Prescriptive versus listed

Prescriptive systems have been tested and verified by governmental authorities including DIBt, [10] the British Standards Institute (BSI) and the National Research Council's Institute for Research in Construction. [11] These organisations publish wall and floor assembly details in codes and standards that are used with generic standardised components to achieve the quantified fire-resistance ratings. Germany and the UK publish prescriptive systems in standards such as DIN4102 Part 4 (Germany) [12] and BS476 (United Kingdom).

Listed systems are certified by testing in which the installed configuration must comply with the tolerances and materials set out in the certification listing. The United Kingdom is an exception to this as certification is required but not testing[ citation needed ].

Countries with optional certification

Fire tests in the UK are reported in the form of test results but building authorities do not require written proof that the materials that have been installed on site are actually identical to the materials and products that were used in the test. The test report is often interpreted by engineers as the test results are not communicated in uniformly structured listings. In the UK, and other countries which do not require certification, the proof that the manufacturer has not substituted other materials apart from those used in the original testing is based on trust in the manufacturer.

See also

Related Research Articles

<span class="mw-page-title-main">Firewall (construction)</span> Barrier used to prevent the spread of fire through or between structures

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.

<span class="mw-page-title-main">Vermiculite</span> Hydrous phyllosilicate mineral which expands significantly when heated

Vermiculite is a hydrous phyllosilicate mineral which undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently; commercial furnaces can routinely produce this effect. Vermiculite forms by the weathering or hydrothermal alteration of biotite or phlogopite. Large commercial vermiculite mines exist in the United States, Russia, South Africa, China, and Brazil.

<span class="mw-page-title-main">Bulkhead (partition)</span> Vertical partition inside a ship

A bulkhead is an upright wall within the hull of a ship, within the fuselage of an airplane, or a car. Other kinds of partition elements within a ship are decks and deckheads.

<span class="mw-page-title-main">Fire door</span> Fire resistant 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.

<span class="mw-page-title-main">Fireproofing</span> Rendering something (structures, materials, etc.) resistant to fire, or incombustible

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").

<span class="mw-page-title-main">Intumescent</span> Substance that swells as a result of heat exposure

An intumescent is a substance that swells as a result of heat exposure, leading to an increase in volume and decrease in density. Intumescence refers to the process of swelling. Intumescent materials 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 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 fire-resistance rating of a wall or floor assembly intended to impede the spread of fire and smoke.

<span class="mw-page-title-main">Firestop pillow</span>

Firestop pillows are passive fire protection items used for firestopping holes to achieve fireproofing. The various kinds of firestop pillows are intended to slow the spread of fire. They are often used to meet fire-resistance ratings in conduits that need frequent access.

Within the context of building construction and building codes, occupancy is the use 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.

<span class="mw-page-title-main">Cable tray</span> Electrical-cable-supporting structure

In the electrical wiring of buildings, a cable tray system is used to support insulated electrical cables used for power distribution, control, and communication. Cable trays are used as an alternative to open wiring or electrical conduit systems, and are commonly used for cable management in commercial and industrial construction. They are especially useful in situations where changes to a wiring system are anticipated, since new cables can be installed by laying them in the tray, instead of pulling them through a pipe.

<span class="mw-page-title-main">Circuit integrity</span>

Circuit integrity is how little can a fire affect an electrical circuit's operation. It is a form of fire-resistance rating. Circuit integrity is achieved via passive fire protection means, which are subject to listing and approval use and compliance. Alternatively, cable construction and materials can achieve fire-resistance ratings on their own such as mineral-insulated copper-clad cable, or MI cable.

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.

<span class="mw-page-title-main">Fire test</span>

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.

<span class="mw-page-title-main">Pressurisation ductwork</span>

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

<span class="mw-page-title-main">Smoke exhaust ductwork</span>

Smoke exhaust ductwork, in Europe, is typically protected via passive fire protection means, subject to fire testing and listing and approval use and compliance. It is used to remove smoke from buildings, ships or offshore structures to enable emergency evacuation as well as improved firefighting. In North America, fireproofed ductwork may be used for the purpose of smoke exhaust, but it is more common to use unfireproofed return air ductwork, whereby no fire testing or listings are employed to qualify the ductwork for this use.

<span class="mw-page-title-main">Grease duct</span>

A grease duct is a duct that vents 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 part of the building's passive fire protection system. The cleaning schedule is typically dictated by fire code or related safety regulations.

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.

<span class="mw-page-title-main">Fire damper</span> Type of passive fire protection

Fire dampers are passive fire protection products used in heating, ventilation, and air conditioning (HVAC) ducts to prevent and isolate 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.

<span class="mw-page-title-main">Penetrant (mechanical, electrical, or structural)</span>

Penetrants, or penetrating items, are the mechanical, electrical or structural items that pass through an opening in a wall or floor, such as pipes, electrical conduits, ducting, electrical cables and cable trays, or structural steel beams and columns. When these items pierce a wall or floor assembly, they create a space between the penetrant and the surrounding structure which can become an avenue for the spread of fire between rooms or floors. Building codes require a firestop to seal the openings around penetrants.

References

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  2. "ASTM E119 – 15 Standard Test Methods for Fire Tests of Building Construction and Materials". www.astm.org. Retrieved 2015-09-25.
  3. "Fachbereich 1 Baustoffe und Brandschutz". Archived from the original on 2008-05-26. Retrieved 2008-01-15.
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  6. "Building Code Acceptable Solutions and Verification Methods". Ministry of Business, Innovation and Employment. Retrieved 2015-09-25.
  7. "Miami-Dade County - Building Code Compliance Office". Archived from the original on 2008-01-16. Retrieved 2008-01-15.
  8. "MCFRS-Fire Code". www.montgomerycountymd.gov. Archived from the original on 2008-06-05.
  9. "NRC: 10 CFR 50.48 Fire protection". www.nrc.gov. Retrieved 2015-09-25.
  10. "DIBt – Deutsches Institut für Bautechnik". www.dibt.de. Retrieved 2015-09-25.
  11. "Institute for Research in Construction - NRC-IRC". Archived from the original on 2007-09-13. Retrieved 2007-09-16.
  12. "NABau". din.de.