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Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a fire-resistance rating. The term "fireproofing" is a trade term, which is also reflected in common North American construction specifications, which does not necessarily mean that an item cannot ever burn or be rendered inoperable as a result of fire exposure. It relates to measured performance under specific conditions of testing and evaluation. Fireproofing does not allow treated items to be entirely unaffected by any fire, as conventional materials are not immune to the effects of fire at a sufficient intensity and/or duration.
- Commercial construction
- Residential construction
- Industrial construction
- Marine (ships)
- Offshore construction
- Tunnel concrete walls and ceilings or linings
- Under and above ground mining operations
- Structural steel to keep below critical temperature ca. 540 °C
- Electrical circuits to keep critical electrical circuits below 140 °C so they stay operational
- Liquified petroleum gas containers to prevent a BLEVE (boiling liquid expanding vapour explosion)
- Vessel skirts and pipe bridges in an oil refinery or chemical plant to keep the structural steel below critical temperature ca. 540°
- Concrete linings of traffic tunnels
Asbestos was one material historically used for fireproofing, either on its own, or together with binders such as cement, either in sprayed form or in pressed sheets, or as additives to a variety of materials and products, including fabrics for protective clothing and building materials. Because the material has proven to cause cancer in the long run, a large removal and replacement business has been established.
Endothermic materials have also been used to a large extent and are still in use today, such as gypsum, concrete and other cementitious products. More highly evolved versions of these are used in aerodynamics, intercontinental ballistic missiles (ICBMs) and re-entry vehicles, such as the space shuttles.
Alternative fireproofing methods
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Among the conventional materials, purpose-designed spray fireproofing plasters have become abundantly available the world over. The inorganic methods include:
- Gypsum plasters
- Cementitious plasters
- Fibrous plasters
The industry considers gypsum-based plasters to be "cementitious", even though these contain no Portland, or calcium aluminate cements. Cementitious plasters that contain Portland cement have been traditionally lightened by the use of inorganic lightweight aggregates, such as vermiculite and perlite.
Gypsum plasters have been lightened by using chemical additives to create bubbles that displace solids, thus reducing the bulk density. Also, lightweight polystyrene beads have been mixed into the plasters at the factory in an effort to reduce the density, which generally results in a more effective insulation at a lower cost. The resulting plaster has qualified to the A2[clarification needed] combustibility rating as per DIN4102.[full citation needed] Fibrous plasters, containing either mineral wool, or ceramic fibres tend to simply entrain more air, thus displacing the heavy fibres. On-site cost reduction efforts, at times purposely contravening the requirements of the certification listing, can further enhance such displacement of solids. This has resulted in architects' specifying the use of on-site testing of proper densities to ensure the products installed meet the certification listings employed for each installed configuration, because excessively light inorganic fireproofing does not provide adequate protection and are thus in violation of the listings.
Proprietary boards and sheets, made of gypsum, calcium silicate, vermiculite, perlite, mechanically bonded composite boards made of punched sheet-metal and cellulose reinforced concrete have all been used to clad items for increased fire-resistance.
An alternative method to keep building steel below its softening temperature is to use liquid convection cooling in hollow structural members. This method was patented in the 19th century although the first prominent example was 89 years later.
The following examples of fraud are preventable when documentation is required and checked to ensure that all installed configurations fall within the tolerances of active certification listings.
- Entraining too much air in inorganic systems, thus reducing densities below fire-tested, saves on materials and labour.
- Spraying inorganic spray fireproofing materials over through-penetrations and building joints that should be firestopped, not fireproofed. This practice negates fire-separation integrity. Firestops must precede spray fireproofing.
- Substitution of intumescent and/or endothermic fireproofing coatings with less expensive paints that physically resemble the passive fire protection products, sometimes involving re-use of packaging and de-canting of contents.
- The American and Canadian nuclear industries have, historically, not insisted on listing and approval use and compliance, on the basis of the use of accredited certification laboratories. This has allowed the use of Thermo-Lag 330-1, for which the basis of testing has been proven to be faulty, resulting in millions of dollars of remedial work. The Thermo-Lag scandal came to light as a result of disclosures by American whistleblower Gerald W. Brown, who reported the deficiencies in fire testing to the Nuclear Regulatory Commission. Presently, product certification of fireproofing and firestopping remains optional for systems installed in nuclear power plants both in Canada and the United States.
Spray fireproofing products have not been qualified to the thousands of firestop configurations, so they cannot be installed in conformance of a certification listing. Therefore, firestopping must precede fireproofing. Both need one another. If the structural steel is left without fireproofing, it can damage fire barriers and a building can collapse. If the barriers are not firestopped properly, fire and smoke can spread from one compartment to another.
Traffic tunnel fireproofing
Traffic tunnels may be traversed by vehicles carrying flammable goods, such as petrol, liquified petroleum gas and other hydrocarbons, which are known to cause a very rapid temperature rise and high ultimate temperatures in case of a fire (see the hydrocarbon curves in fire-resistance rating). Where hydrocarbon transports are permitted in tunnel construction and operations, accidental fires may occur, resulting in the need for fireproofing of traffic tunnels with concrete linings. Traffic tunnels are not ordinarily equipped with fire suppression means, such as fire sprinkler systems. It is very difficult to control hydrocarbon fires by active fire protection means, and it is expensive to equip an entire tunnel along its whole length for the eventuality of a hydrocarbon fire or a BLEVE.
Concrete exposed to hydrocarbon fires
Concrete, by itself, cannot withstand hydrocarbon fires. In the Channel tunnel that connects United Kingdom and France, an intense fire broke out and reduced the concrete lining in the undersea tunnel down to about 50 mm. In ordinary building fires, concrete typically achieves excellent fire-resistance ratings, unless it is too wet, which can cause it to crack and explode. For unprotected concrete, the sudden endothermic reaction of the hydrates and unbound humidity inside the concrete causes such pressure as to spall off the concrete, which then winds up in small pieces on the floor of the tunnel. This is the reason why laboratories insert humidity probes into all concrete slabs that undergo fire testing even in accordance with the less severe building elements curve (DIN4102, ASTM E119, BS476, or ULC-S101). The need for fireproofing was demonstrated, among other fire protection measures, in the European "Eureka" Fire Tunnel Research Project, which resulted in building codes for the trade to avoid the effects of such fires upon traffic tunnels. Cementitious spray fireproofing must be certification listed and applied in the field as per that listing, using a hydrocarbon fire test curve such as the one that is also used in UL1709.
The traditional method for constructing fireproof vaults to protect important paper documents has been to use concrete or masonry blocks as the primary building material. In the event of a fire, the chemically bound water within the concrete or masonry blocks will be forced into the vault chamber as steam. The steam will soak the paper documents to keep them from burning. This steam will also help keep the temperature inside the vault chamber below the critical 176.7 °C (350 °F) threshold, which is the point at which information on paper documents is destroyed. The paper can later be remediated with a freeze drying process, if the fire is extinguished before internal temperatures exceed 176.7 °C (350 °F). An alternate less expensive and time-consuming process is using dry insulating material.
This traditional vault construction method is sufficient for paper documents, but the steam generated by concrete/masonry structures will destroy contents that are more sensitive to heat and moisture. For example, information on microfilm is destroyed at 65.5-degrees C (150-degrees F. a.k.a. Class 150) and magnetic media (such as data tapes) lose data above 51.7-degrees C (125-degrees F. a.k.a. Class 125). Fireproof vaults built to meet the more stringent Class 125 requirement are called data-rated vaults.
All components of fireproof vaults must meet the fire protection rating of the vault itself, including doors, HVAC penetrations and cable penetrations
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- Brominated flame retardant
- Cable tray
- Channel tunnel
- Circuit integrity
- Fire protection
- Fire-resistance rating
- Flame retardant
- Gerald W. Brown
- Liquified petroleum gas
- Listing and approval use and compliance
- Passive fire protection
- Product certification
- Sodium silicate
- Fisher, Arthur (May 1970). Water-Filled Columns Keep Building Frames Cool in Fires. Popular Science. Retrieved 27 Jan 2012.
- see U.S. Steel Tower
- National Fire Protection Association 232 "Protection of Records"
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