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What issues must I consider for passive fire protection?

Integrated systems for passive fire protection

To choose the most suitable treatment you need to take into account such important issues as the surfaces to be treated, the methods that can be used, the different types of fire that may occur and current regulations.

Why do I need fire-protection?

Apart from common sense, national and EU standards governing construction materials (CPR EU 305 2011) place fire safety as an essential requirement immediately after structural aspects. When talking about fire protection this includes all provisions aimed at keeping to a minimum damage to people and property and to limit the consequences of such damage. 

Active and passive protection.

Active fire protection aims to reduce the effects of fire by early detection and rapid extinguishing brought about by human action or by the activation of equipment such as sprinkler systems, alarms and fire extinguishers. 
Passive fire protection, on the other hand, has as its aim limiting the effects of the fire so as to make it possible to evacuate the building and to make people and property safe within a certain time period. This is not an alternative to active protection but an approach to fire safety that is independent of human or mechanical intervention. Passive protection systems come into action autonomously as soon as the surfaces or materials to be protected come into contact with flame or high temperatures. Passive fire protection, in the sense of the fire resistance of structural elements, is generally indicated in legislation and standards by the abbreviation REI, accompanied by a number representing the minimum duration in minutes of the required resistance

The REI abbreviation

REI represents the initials of three French words
  • Resistance = R = resistance/load bearing capacity
  • Entretenir = E = integrity
  • Isolement = I = insulation
Other parameters exist that, while currently less well known, will be increasingly demanded in the future since they are referred to in the new national and EU standards. 
The REI rating defines the capacity of a building, or part of it, or of a construction element, to maintain its various properties for a fixed time.
Not all the performance properties are always required at the same time. For load-bearing elements, mechanical resistance (R) over time is always required, while for non-load-bearing compartmentalising elements such as dividing walls, resistance (R) is an irrelevant factor while integrity (E) and insulation (I) become significant.
It is therefore possible to find specifications of the type: R 120, RE 120, REI 120 and also EI 120 meaning requirements for the minimum duration of individual or multiple performance factors, in this case 120 minutes.
The fire-resistance durations are specified by the relevant standard or regulation, being typically 15, 30, 45, 60, 90, 120, 180 and 240 minutes, expressing the time in minutes during which fire resistance must be guaranteed.

Different solutions for different materials

For passive fire protection it is possible to choose from among a number of products or protection systems, each with its own pros and cons.
Reactive paints – field of application steel, cast iron, wood, brickwork, reinforced concrete and pre-stressed concrete.
Pros: as well as being easy to apply, these are particularly popular because they leave the aesthetic appearance of the protected surface unchanged. Reduced weight, high mechanical strength and reduced bulk are further factors making this system popular. Moreover, used on metal structures they team perfectly with ...
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Reactive/intumescent paints

Reactive coatings are based on principles that have been known about for centuries, but it was only midway through the last century that major developments were made in both their formulas and applications. Their intumescence is based on a sequence of chemical and physical mechanisms that lead, as soon as the protective coating is exposed to heat, to the formation of a carbonaceous foam that acts as a protective barrier. One layer of a reactive paint barely 1mm thick can produce some centimetres of foam. This makes it possible for reactive paints to provide high fire-resistance ratings to structural elements without altering their lines, shapes and architectural geometry. Moreover, they can be overpainted with various types of finishing paints or varnishes, making them not only resistant to atmospheric agents but their finish and colour can also enhance the aesthetic effect. Amotherm brand products provide effective, fully tested passive fire-protection for structures and materials.
FOTO: intumescence

Soft plasters

Lightened fire-resistant soft plasters are usually formulated on a base of plaster/cement to which inert ingredients of various types have been added, such as vermiculite, polystyrene and cellulose, to lighten the specific weight and increase the mass and insulating power compared to ordinary plaster. Each type of plaster has its own specific heat insulating co-efficient (λ). The thickness of plaster to be applied to obtain the desired fire-resistance rating is calculated according to the structure to which it is to be applied, the critical temperature required and, by applying the insulation co-efficient, it is possible to calculate the insulating thickness that must be used. Since these plasters are not only used on concrete but also metal surfaces, their cohesion and adherence are of critical importance. AMONN has joined forces with GRACE, the world leader in the production of lightened fire-resistant plasters, and recommends the various Monokote solutions for passive fire protection. 

Resistance and reaction

In passive fire protection differentiation is made between products designed to slow heat propagation in order to limit the damage to buildings and other structures (resistance), and products designed to reduce the combustion capacity of normally inflammable materials (reaction). For non-combustible structural elements the focus is on raising their resistance to fire for a determinate period of time. For combustible construction elements, such as wood, in addition to their fire resistance, the requirement is that the wood should not contribute to triggering fire and feeding its propagation. The main factor for the resistance requirement is the length of time, while the fire reaction requirement is not linked to any time factor, the material must comply with the combustibility classes provided for by the regulations

Intumescent or fire-proofing paints

Two defence mechanisms are used for protective paint systems, the first being intumescence while the second involves increasing the fire-proof properties of the materials. 
  • The word intumescence is derived from the Latin word intumescens “swelling”, and that is exactly how this defence mechanism works in paints that, when they are subjected to heat or flame, swell up and create a carbonaceous layer that acts as a protective barrier. The thermal insulation power of the foam generated by the chemical and physical process triggered by the rise in temperature increases the fire-resistance of the structure to which it is applied. 
  • A paint is defined as fire-proofing if it possesses properties that notably reduce the combustion capacity of the wood surface to which it is applied. Fire-proofing paints use chemical reactions intended to extinguish the flames or to limit their propagation. Fire-proofing paint therefore, alters the reaction to fire of the materials to which it is applied. 
FOTO: Column with intumescence and wood after being subjected to Class 1