Fire safety and protection systemsRob Gardiner, of Armstrong World Industries, looks at passive fire protection systems and the role suspended ceilings play in protecting a building against fire
It doesn't take much to start a fire: just the right combination of heat, oxygen and fuel. In theory, eliminating a fire or preventing its spread simply requires the removal of one of these elements. But whereas a fire can start almost instantaneously, putting it out is almost never as swift.
In July 2005, the Office of the Deputy Prime Minister issued a revised copy of Approved Document B for consultation to help limit the number of fires and minimise the consequences.
The document provides guidance on the level of fire performance necessary to comply with the requirements of Part B of the UK Building Regulations. The final version (volumes one and two) has now been published and will come into force on 6 April 2007.
Fire protection systems are categorised as either active or passive. Automated detectors and sprinklers are considered active, and passive methods include the use of suitably tested materials and construction techniques that limit the development of a fire and protect the building's structure.
Suspended ceilings, could be an example of this, contributing towards the protection of the building in two ways.
The first depends on a material's fire reaction performance. Requirement B2 of Approved Document B demands that all interior linings within a building, including suspended ceilings, must "adequately resist the spread of flame over their surfaces".
It further states that if those materials are ignited, they should have a rate of heat
release or fire growth "which is reasonable in the circumstances".
In order to be sure that building components are able to fulfil these requirements, there are appropriate test methods (British Standards or Euro Norms). For suspended ceilings these have historically been BS 476. However this is set to change.
Part B of the UK Building Regulations was amended in 2002 to include European test methods for fire reaction and resistance. The British Standard and the harmonised European standards can currently be used to show compliance to the Building Regulations.
But as part of the process of technical harmonisation of standards within Europe, the new suspended ceilings product standard, BS EN 13964, was published in 2004 and only references European test methods.
This leads the way for the CE marking of suspended ceilings that will become mandatory in most European countries at the end of the period of coexistence (1 July 2007), which will mean that BS 476 testing methods for fire reaction will no longer be acceptable.
But whether fire reaction testing is carried out to BS 476 or to the new European standards, there are similar concepts involved. These include the ignitability or spread of flame across the surface of the tile and the rate of heat release or combustibility of the product.
The European test methods also introduce measures for smoke and flaming droplets, although Approved Document B does not currently give a set of detailed performance requirements for these.
Meeting the above criteria for fire reaction will limit the time taken for a fire to grow, but once it has fully developed, the main emphasis moves to fire resistance.
This falls under the remit of Requirement B3 of Approved Document B, which states that "the building shall be designed and constructed so that, in the event of a fire, its stability will be maintained for a reasonable period".
Fire resistance therefore relates to the protection of the building's structure, and should enable people to get out safely.
Whereas all suspended ceilings require the appropriate fire reaction performance, not all will be required to provide fire resistance.
However, when they are used for fire resistance, the choice of grid system and method of installation are critical.
They can also protect various types of flooring, such as mezzanine or timber, and provide protection to load-bearing steel beams, provided that they are installed as tested.
As with fire reaction, there are European standards for fire resistance, although currently there is not a single test method that has been deemed acceptable to all.
Therefore, either the British Standard tests for fire resistance (BS 476 parts 20-23), or those European tests permitted in Approved Document B, can be used to prove fire resistance performance to the UK Building Regulations requirements.
Although there are limitations to the fire resistance performance that suspended ceilings provide, there are other construction techniques and structures that will ensure the integrity and stability of the building.
When it comes to fire reaction however, suspended ceilings can meet the Building Regulations requirements when tested to either the European or British standards.
Rob Gardiner is Technical Sales Manager, UK & ROI at Armstrong World Industries Ltd.