3m Fireproofing

[Placido Teofilo]

Fireproofing is rendering something (structures, materials, etc.) resistant to fire, or incombustible; or material for use in making anything fire-proof.[1] 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").

Applying a certification listed fireproofing system to certain structures allows them to have a fire-resistance rating. The term "fireproofing" may be used in conjunction with standards, as reflected in common North American construction specifications. An item classed as fireproof is resistant in specified circumstances, and may burn or be rendered inoperable by fire exceeding the intensity or duration that it is designed to withstand.

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 was later proven to cause cancer, a large removal-and-replacement industry 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.

Historically, these masonry encasement methods use large amounts of heavy materials, thus greatly increasing the load to the steel frame. Newer materials and methods have been developed to resolve this issue. The following lists both older and newer methods of fireproofing steel beams (i-beams):[7]

Gypsum plasters include chemical additives to create bubbles that displace solids, thus reducing the bulk density. Lightweight polystyrene beads may be 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.

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 temperature below the critical strength limit is to use liquid convection cooling in hollow structural members.[9] This method was patented in the 19th century although the first prominent example was 89 years later.[10]

Traffic tunnels may be traversed by vehicles carrying flammable goods, such as petrol, liquefied 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.

Concrete cannot, by itself, withstand severe hydrocarbon fires. In the Channel Tunnel that connects the United Kingdom and France, an intense fire broke out and reduced the concrete lining in the undersea tunnel down to about 50 mm.[citation needed] 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 generates pressure high enough to spall off the concrete, which falls in small pieces on the floor of the tunnel. Humidity probes are inserted into all concrete slabs that undergo fire testing to test for this, even for 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 gave rise to 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 used in UL1709.[11]

Fireproof vaults to protect important paper documents are usually built using concrete or masonry blocks as the primary building material.[citation needed] In the event of a fire, the chemically-bound water within the concrete or masonry blocks is forced into the vault chamber as steam, which soaks the paper documents to keep them from igniting.[citation needed] This steam also helps 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.[citation needed] 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).[citation needed] An alternate less expensive and time-consuming construction method is using dry insulating material.[citation needed]

This vault construction method is sufficient for paper documents, but the steam generated by concrete and masonry structures will destroy contents that are more sensitive to heat and moisture. For example, information on microfilm is destroyed at 65.5 C (149.9 F) (a.k.a. Class 150)[citation needed] and magnetic media (such as data tapes) lose data above 51.7 C (125.1 F) (a.k.a. Class 125).[citation needed] Fireproof vaults built to meet the more stringent Class 125 requirement are called data-rated vaults.[citation needed]

Fireproofing is to extend the time an item can be exposed to fire before it fails. In construction this is referred to as passive fire-protection as it does not extinguish the fire but rather prevents failure. Typically this is done by applying a fireproofing material to structural members.

While the term fireproofing may seem to imply that an item cannot burn or fail, this is not the case. In reality, no building material or system is completely fireproof. All physical structures and components have limits and can be irreparably damaged by fire. A more proper term would be fire resistant as it only protects the structure for a prescribed period of time.

Although there are different materials and methods of doing this, all systems follow the same basic principle. A product is used to separate the item from the fire, which will insulate and delay the transfer of heat. This can be achieved in different ways but the basic principle always stays the same.

Regardless of the above, fireproofing a structure is an effective way of preserving structural integrity for a period of time during a fire. This is important as it allows people a chance to escape and gives firefighters the ability to safely enter the structure and provide fire rescue services.

Fireproofing is required in order to ensure a structure or a part of a structure will not fail for a period of time during a catastrophic fire. National and regional building codes will determine what fire-rating is required for a given structure.

The required rating usually depends on the construction type and use group. There are also often more than one use group in a structure. In these instances a separation between uses may be required with a fire rating higher than the rest of the structure.

Buildings may be designed and constructed with fire resistance-rated walls, floors and ceilings and a design must be provided showing all components of a given assembly and the provided rating. When all details of a design are followed, the assembly as a whole is to be considered fire-rated. This is often referred to as a fire-rated assembly.

A thorough understanding of building code is needed in order to determine the fire ratings needed for your project. These are typically called out by the architect and can be found in the construction documents.

While there are different methods to fire rate a structure, steel construction is generally fire rated with a fireproofing material. This will usually be either cementitious (spray fireproofing) or intumescent fireproofing.

When designing a project and specifying a product, care must be taken to choose the most appropriate material that complies with the code requirements of the structure getting rated. Aside from the required rating, there are variables in material capabilities and properties. Code may require materials with specific characteristics depending on building height and other factors. Additionally, not all materials are created equal and the environment and location play a big part in choosing the correct product. Some situations may require materials with specific approvals and properties.

Fireproofing contractors will use specialty machinery to mix water and material. Then using compressed air, they atomize and spray apply the fireproofing to the correct thickness for the required rating. When the cementitious material completely dries, it forms a barrier. This coating will act as an insulator and significantly delay heat transfer. In the event of a fire this will protect the building structure from failure for the prescribed time.

Not all cementitious fireproofing is created equal, so you need to choose a product that is best suited for your project as well as the environmental conditions your building will encounter. Some fireproofing is more durable, and some are better suited for high-moisture areas. Some products are designed for conditioned spaces while others are tested for durability in freeze-thaw cycles.

In addition to the above, cementitious fireproofing comes in different densities which are broken down into three categories, low, medium and high density. Higher density materials will have different properties then lower density materials. Higher density materials may be required by code depending on different factors.

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