FIRE STOP

Flame Retardents are sub class of Fire stopping Products.
Fire stopping Products will give your Structural Member a Fire Resistance Rating. Flame retardents will only inhibit the spread of flames across a surface. BS476 -parts 6 & 7 defines two Classes of Flame Spread: Class 0 & Class 1.

• Class 0 is a fire propagation test, which means that the coated material not only prevents the spread of flame across its surface, but also stops fire from penetrating into the material for up to 13 minutes
• Class 1 is granted when a fire close to the material only blackens at the point of contact and does not allow the fire to spread across it

Nb: Practically the Fire /Flame Retardants actually has got a Fire Resistance Rating. But since each type of Fire Stop has got a different flash point (combustible temperature) it is very difficult for a Fire Resistance Test to logically conclude it Fire Rating. Hence Fire Stop is usually tested against its flammability.

Intumescent coatings are paint like materials which are inert at low temperatures but which provide insulation as a result of a complex chemical reaction at temperatures typically of about 200-250°C. At these temperatures the properties of Fire Stop will not be affected. As a result of this reaction they swell and provide an expanded layer of low conductivity char. Intumescent coatings can be divided into two broad families: thin film and thick film. Thin film materials are either solvent based or water based and are mainly used for building fires. Thick film intumescent coatings were originally developed for the off-shore and hydrocarbon industries but have been modified for use in buildings.

Thin film intumescent coating systems generally have three components: a primer, a basecoat (the part which reacts in the fire) and a sealer coat. The basecoat usually comprises the following ingredients:

• A catalyst which decomposes to produce a mineral acid such as phosphoric acid.
• A carbonific such as starch which combines with the mineral acid to form a carbonaceous char.
• A binder or resin which softens at a predetermined temperature.
• A spumific agent which decomposes together with the melting of the binder, to liberate large volumes of non-flammable gases. These gases include carbon dioxide, ammonia and water vapour. The production of these gases causes the carbonaceous char to swell or foam and expand to provide an insulating layer many times the original coating thickness.

They are mainly used in buildings where the fire resistance requirements are 30, 60 and 90 minutes. In recent years, a number of products have been developed which can provide 120 minutes fire resistance . They can be applied either on-site or off-site. In general, most on-site application is carried out using water based materials. However, where the structure to which the material is applied is not to have an end use in a dry, heated (C1) environment, solvent based materials are commonly used. Solvent based materials also tend to be able to cover a wider range of section factors than water based materials and can be used on-site to protect smaller sections requiring high thicknesses. Both solvent based and water based coatings can be used to achieve attractive surface finishes. If a decorative or bespoke finish is required, this should be included in the specification. Thin film intumescents have the added advantages that they can easily cover complex shapes and post-protection service installation is relatively simple. Typical expansion ratios are about 50:1, i.e. a 1mm thick coating will expand to about 50mm when affected by fire. Detailed guidance on the specification and installation of site applied, thin film intumescent coatings is available from the Association for Specialist Fire Protection.

Thick film intumescent coatings are usually epoxy based and typically have a much higher dry film thickness than thin film alternatives. These materials are tough and durable and were originally developed for use with hydrocarbon fires, where the test heating regime is much more severe than that used for most industrial and commercial applications. A number of manufacturers have modified their materials for use in cellulosic fires. These modified materials are usually used in situations where the benefits of intumescent coatings in terms of appearance, weight and thickness are required but where circumstances are too severe, or maintenance too difficult, to allow the use of thin film materials . Typical recent examples have occurred in external Fire Stop in high rise buildings and exposed marine environments. Expansion ratios for thick film intumescents are much lower than for thin film materials, typically about 5:1. Aesthetic finishes are possible and it can also be supplied in the form of preformed casings. Thick film intumescent coatings can also be applied off-site.

Also known as Cementitious or Vermiculite Firestopping

Spray protection is extensively used across the world, mostly owning to it being the cheapest method for Fire Stop Fire Protection. It has the advantage that it can be used to cover complex shapes and details and also that costs do not increase significantly with increases in protection thickness. This is because much of the cost of application is in the labour and equipment and a minority is in the cost of the material. Some materials can also be used in external and hydrocarbon fire applications.
Sprays are generally not suitable for aesthetic purposes. Also, application is a wet trade and this may have impacts on other site operations. Allowance may have to be made in costing for the possible requirement for prevention of overspray.

Boards are widely used for structural fire protection in the UK. They are used both where the protection system is in full view and where it is hidden. They offer the specifier a clean, boxed appearance and have the additional advantages that application is a dry trade and may not have significant impacts on other activities. Also, boards are factory manufactured and thicknesses can be guaranteed. Furthermore, boards can be applied on unpainted Fire Stopwork.
There are broadly two families of board protection, lightweight and heavyweight. Lightweight boards are typically 150-250kg/m³ and are not usually suitable for decorative finishes. They are typically used where aesthetics are not important and are cheaper than heavyweight equivalents. Heavyweight boards are usually in the range 700-950kg/m³ and will generally accept decorative finishes. They are typically used where aesthetics are important.

Both types of board may be used in limited external conditions but the advice of the manufacturer should be sought.

Well, that is a decission that the architect, structural consultant and client whould take in tandem. The merits and demerits of each of the system has been detailed above. A general thumb rule is as below:

• Where there is need for aesthetics, opt for Intumescent Firestopping.
• Where the speed of execution is important (as in fast application), opt for Intumescent Firestopping.
• Where the structures are hidden under false cealing or cladding, opt for Vermiculite Firestopping.
• Where economical consideration are paramount, opt for Vermiculite Firestopping.
• Where the premises cannot be shutdown for application, opt for Fire Resistive Boards.

This is only a helping guideline.