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Europe harmonises fire safety

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The second in a bi-monthly series of articles by Lawrence Webster Forrest examining key fire safety issues

New European performance standards will provide the regulatory bodies of the individual member states with effective, all-encompassing test methods. Some of the new standards are set to change the face of UK fire testing and specification.

As Europe draws ever closer, manufacturers of building products are increasingly looking for undiscovered sectors of the European Union with which to trade. Previously, expansion into such markets has been considered troublesome and fraught with red tape.

Until now, much of this bureaucracy has revolved around a manufacturer's ability to comply with the fire-performance standards of the country to which they are exporting. The requirements of national fire tests can vary significantly from country to country. Differences can include parameters as diverse as the scale of the test, the maximum size of samples, the thermal exposure conditions, the ventilation provisions and sample fixing details.

The restrictions applying to the country into which a product is being exported can differ greatly from those applying to the product's country of origin, and have been recognised as a major stumbling block to barrier-free European commerce.

With this in mind, the Construction Products Directive (CPD) was implemented in June 1991 in an attempt to remove trade barriers between EU member states by providing a framework for the harmonisation of test methods and product specification.

The directive was designed to cover all products which are intended as an integral and permanent part of construction works. It contains six health and safety-related 'essential requirements' that detail the minimum standard a product or system must achieve in order for it to attain its CE marking.This is a mandatory requirement for placing products into the European market and is similar in purpose to that of the current British Standards Kitemark.The six essential requirements are:

mechanical resistance and stability;

safety in the case of fire;

hygiene, health and the environment;

safety in use;

protection against noise; and energy economy and heat retention.

Each of the requirements is technically developed through a series of interpretative documents (IDs), of which safety in the case of fire (ID2), will be examined in this article.

The fire-test methods contained within the interpretative document on safety are being drawn up by the Technical Committee (TC) 127 of the European Standards Organisation (CEN). UK input into these discussions, and the briefing of UK delegations, is coordinated by the British Standards Institute (BSI).The preparation of test methods in support of the directive covers two primary areas, fire-resistance tests and reaction to fire tests.

The fire-resistance testing of building products, components and systems is being conducted by way of a number of new European standards based on concepts which are already internationally accepted (see table below).The many minor technical anomalies between national fire-resistance tests can produce varying results for identical specimens of a product.The newly developed standards are intended to lead to greater harmonisation.

One of the more significant issues being addressed by the European standards is the variable severity of the thermal exposure experienced by test samples in different countries, due to the difference in construction and configuration of furnace set-ups. In an attempt to address this, the use of the 'plate thermometer' was developed as a more reliable tool for monitoring and regulating the internal conditions of the furnace (see diagram).It is widely believed that the use of this apparatus, as opposed to that of the standard 'point type' thermocouples, will provide reliable and uniform test results across Europe.

The fire-resistance performance of a product is classified on the outcome of the results obtained for a single specimen.The primary classifications are:

Load-bearing capacity (R) - the ability of a loadbearing element to support its test load without exceeding a specified criteria with respect to either or both the extent of, or rate of, deformation.

Fire integrity (E) - the ability of a separating element to contain a fire to specified criteria for collapse, freedom from holes, cracks and fissures and sustained flaming on the unexposed face.

Fire insulation (I) - the ability of a separating element to restrict the temperature rise of the unexposed face below specified levels.

The letters are assigned to a specimen after the test in a number of allowable combinations, signifying the results category followed by the relevant time compliance. For example E30 means 30-minute integrity only; REI60 means that the sample offers 60minute load-bearing capacity, integrity and insulation.

Certain products can also attain other classifications, for example demonstrating their resistance to emission of thermal radiation (W), self closing capabilities (C) and smoke leakage potential (S).

At present, the use of test data from one particular specimen to assess the likely fire-resistance performance of another specimen is not permitted.

However, it is intended that test reports produced in support of the European standard will contain a 'direct field of application'statement that will allow a certain degree of scope for other products than the specimen which was actually tested.This is, after all, only a common sense approach. If, for example, the largest partition system that could possibly be tested was 3m by 3m, it would be unreasonable to impose a limit of that size for real applications just because of furnace restrictions.

In the 'reaction to fire' category every effort has been made to utilise the current European test methods that have a proven track record in providing significant correlations to real fire data.As such, the various test methods (see below) will be incorporated into the new standardised European solution. It is worth noting that many of the UK's own British Standard 476 tests (Fire tests on building materials and structures) are widely regarded as not giving an accurate representation of the 'real fire performance' of a product or a system and, therefore, these have not been included.

Notwithstanding the technicalities of the new standard, the fundamental aspect of the harmonisation process has been the introduction of the new single burning item test.The use of such a test evolved from the requirement of European fire regulations for a standard test to simulate a single item burning close to the corner of a room and growing within the enclosure to the point of flashover.The need for such a test has been highlighted in a number of devastating fires throughout the world and fire regulators have recognised this scenario as the only major fire hazard that has, up until now, gone relatively unassessed.

The test was developed under a European Commission-funded programme conducted by officiallynominated laboratories from each member state under the direction of the European Fire Regulators Group. In the UK, this test development work was conducted by the Fire Research Station, which was nominated by the Department of the Environment, Transport and the Regions.

The aim of the single burning item test is to use the various product test results, and create six Euroclasses of 'reaction to fire' for building products.

Products will achieve a level of classification gauged on their potential contribution to the growth of a fire in its pre-flashover stage.These classes have been designated as follows: class A, which offers no contribution to the development of fire; class B, which offers very limited contribution to fire; class C, which offers limited contribution to fire; class D, which offers acceptable contribution to fire; class E, which offers acceptable reaction to fire; and class F, the test for which has yet to be decided.

Classes A and B identify products that can be safely used in a fully-developed fire of more than 60kW/m 2, while classes C and D are those which perform adequately when exposed to a maximum heat flux of about 40kW/m 2.The exact criterion for distinction between classes is not yet determined.However, with the proposed tests aimed at enabling all necessary parameters to be measured in a technically reliable, repeatable and reproducible manner, the designer should be privy to realistic performance evidence for the first time.

In the single burning item test, the corner of the room is represented by non-combustible boards 1,500mm high by 1,000mm wide and 1,500mm high by 500mm wide mounted perpendicular to one another.

The test product is placed in a specimen holder and fixed in a manner representative of that to be used in its end use condition. Once mounted, the holder and specimen are positioned in the corner of the test enclosure and subject to a carefully regulated ignition source - a propane-fuelled burner capable of producing a 30kW heat output. Pictured above is the exterior of the test rig with the exhaust duct containing the necessary measuring equipment.

The vertical flame effect, where two tests are fully under way, is also shown. This situation presents us with significantly differing results than those that would be obtained under the methods detailed in BS476: Part 7 for the classification of the surface spread of flame of products.

The British Standard utilises an externally-located, applied radiant heat profile to determine horizontal- opposed flame spread over the linings surface. The single burning item test demonstrates the reality - in end-use situations lateral flame spread is generally far slower than vertical flame spread.

This test not only provides us with different results from those usually expected from BS476's Part 7 but, in many cases, opposing ones!

This example demonstrates one instance where anomalies currently occur in the various fire-tests. It only scratches the surface of the internal workings of the relevant authorities and the uphill struggle that is faced in achieving tests which are reliable across the EU.Extensive debate will continue for years to come, even after the standards have been implemented, but it is hoped that the tests will continue and expand their range, without any fundamental problems emerging.

Thanks to the Fire Research Station and BRE for some of the photographs reproduced within this article.To contact Lawrence Webster Forrest call 020 8655 1605 e-mail fire@lwf. co. uk or visit www. lwf. co. uk SETTING THE STANDARDS At present, the world of fire-test standards, like many others, is awash with an array of abbreviations - BSI, ISO, CEN, CEN-ELEC, IEC etc. So, which takes precedence? What accreditation should manufacturers be aspiring to? In order to understand the situation fully, the history of the formation of the various sectors requires explanation.

In 1907, as a result of the large-scale introduction of electricity, the International Electrotechnical Commission (IEC) was the first standards authority to be formed with the express purpose of reducing the hazards of internationally trading electrical appliances that might have been unsuitable for a receiving country's electricity system. It was not until 1948 that the (first non-electric) International Organisation for Standards (ISO) was established. At the time, both the IEC and ISO appreciated that the total agreement on the varying aspects of individual standards would be almost impossible to achieve. For this reason, their standards were to be taken as suggestions or recommendations, to be adopted to a degree chosen by the respective national standards bodies.

This situation remained for a number of years. However, with the formation of the European Community, the lack of standardisation presented considerable difficulties to the vision of free commerce. Consequently, both the CEN-ELEC and the CEN were formed (covering electrical and nonelectrical organisations respectively) to provide a common framework for all European countries to work towards. This attempt at harmonisation was undermined by the fact that, by then, individual countries had working standards implemented into national law for some time and these could not be changed straight away. As such, political practicalities enabled 'national deviations' to be introduced to prevent certain national standards from being altered by the European standards bodies.

In short, once a standard has been accepted as a European standard then it is recognised as being compulsory in all member states of CEN OR CEN-ELEC, subject to agreed deviations.However, ISO and IEC standards are still seen as recommendations only. Until this is changed there will be a fundamental difference between Europe and recognised standards elsewhere.

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