Testing for fire

The Construction Products Directive (CPD) in Europe will take a major step towards full implementation over the next 12 months. This will happen thanks to the publication of the new European fire tests covering the primary areas of reaction to fire, fire resistance and external fire performance of roofs. The purpose of this harmonisation is to remove trade barriers between member states of the European Community.

Fire tests are used to assess the fire performance of a product or material. The purpose of this assessment is typically to classify the product for its intended application. Such classifications are used by regulators as a way of maintaining levels of safety in case of fire, or by property protection specialists to control the potential for losses. This may include loss of contents, damage to building fabric, and lost opportunities due to business interruption.

Many countries currently have their own national fire tests for evaluating the reaction to fire performance, fire resistance of construction products, and external fire performance of roofs. In the UK, these have traditionally involved the BS 476 series of tests. These test methods are referred to in the practical guidance in Approved Document B: Fire safety1, as appropriate methods for demonstrating compliance with the requirements of the Building Regulations 2000.

Commitment brings responsibility
However, with the commitment of the European Union member states to implement the CPD, comes the requirement to enable the use of the new European fire tests within the national regulatory framework. In England and Wales this will be achieved by the publication of a European supplement to Approved Document B, following a period of public consultation. The draft version completed its period of public consultation on 15 February 2002. It will now be amended accordingly.

In the draft European supplement to Approved Document B, it has been necessary to consider the fire performance of a limited number of construction products, in both the BS 476 and the new European tests. This has led to the definition of European classes of performance within the context of their application, as defined in Approved Document B. Special consideration has been given to maintaining a balance between the current levels of perceived safety and the current commercial marketplace.

Reaction to fire
Table 1 summarises the reaction to fire tests and complementary standards that will be used for classifying construction products in the UK and Europe in future. All construction products excluding flooring will be classified as follows: A1, A2, B, C, D, E, and F, according to their performance in the tests EN ISO 1182: 2002, EN ISO 1716: 2002, EN 13823: 2002 and EN ISO 11925-2: 2002.

Floorings will also have seven classifications: A1FL, A2FL, BFL, CFL, DFL, EFL, and FFL, according to their performance in the tests EN ISO 1182: 2002, EN ISO 1716: 2002, EN ISO 11925-2: 2002 and EN ISO 9239-1: 2002. Additional declarations will be made for both sets of classifications. This relates to smoke production in construction products, excluding flooring. However, these additional classifications are not called upon in the draft Approved Document B.

With the exception of EN 13 823: 2002, the single burning item test, all of the harmonised reaction to fire tests were developed from existing methods. In the case of EN 13 823: 2002, a completely new intermediate scale test method has been developed to simulate a single item burning close to the corner of a room – hence the single burning item test.

Fundamental in the development of EN 13 823: 2002 was the correlation of product fire performance characteristics with those in the ISO 9705 room-corner test, the so-called reference scenario. The product fire performance characteristics are associated with the quantity of heat released and the rate at which it is released, in particular, the occurrence of flashover in the ISO 9705 test under different thermal exposure conditions.

The task of defining European reaction to fire classes within the context of the applications as required in Approved Document B has not been a simple one since the various test methods are very different from each other.

The single burning item test measures different quantitative parameters from BS 476-7, the surface spread of test. These two tests are also very different in their thermal exposure conditions. It is therefore not surprising that the traditional ranking and classification of products based upon BS 476-7 is not maintainable with the new fire tests and classification system.

Government assistance
The data to support the development of the European supplement was largely provided through a DETR sponsored Partners in Innovation project2, in which 60 products were tested. Many products were class 0, according the current UK classes, or were from generic product groups that are not regulated within the UK Building Regulations. Data of relevance to the other BS classes of regulated products was therefore limited. Given this restriction, the following proposal for the European supplement to table 10 in Approved Document B has been agreed (see table 2).

Non-combustible materials have been redefined to include those classified as A1 in accordance with EN 13 501-1: 2002 Fire classification of construction products and building elements, Part 1 Classification using data from reaction to fire tests when tested to EN ISO 1182: 2002 Reaction to fire tests for building products – non-combustibility test or BS EN ISO 1716: 2002 Reaction to fire tests for building products – determination of the gross calorific value. In addition, products made from only one or more of the materials considered as class A1, without the need for testing, as defined in Commission Decision 96/603/EC of 4 October 1996 are also included.

Materials of limited combustibility have been redefined to include those classified as class A2 in accordance with BS EN 13 501-1: 2002 Fire classification of construction products and building elements, Part 1 Classification using data from reaction to fire tests when tested to BS EN ISO 1182: 2002 Reaction to fire tests for building products – non-combustibility test or BS EN ISO 1716: 2002 Reaction to fire tests for building products – determination of the gross calorific value and BS EN 13 823: 2002 Reaction to fire tests for building products – building products excluding floorings exposed to the thermal attack by a single burning item.

Focus on solutions
Until now, under the requirements of the CPD, effort has focused on providing a solution to the problem of European standardisation of reaction to fire test methods for wall and ceiling lining products, which form the primary interest in relation to the UK Building Regulations. There is currently no real guidance on testing of other products within the European system.

As a result, confusion and concern has been responsible for increasing interest in the remaining construction products, including linear products, profiled sheets and construction systems – the difficult or so-called exotic products. The issues relating to end use testing and the appropriate reference scenarios still require final resolution by the European Commission.

Cables
Some countries have fire performance requirements for cables used in buildings. Within Europe, cables have now been encompassed in the CPD, which means that, where required, they will be tested, using a European system of fire test methods and classification.

Currently the system of reaction to fire tests and classification is the same as for all construction products, except flooring. However, it has been noted by the European Commission that: "The treatment of some families of products (pipes, ducts, cables etc), is still under review and may necessitate an amendment to this decision".

As a consequence, the European cable industry is currently working with the European Commission on the development of a European system for testing and classification of cables.

Fire resistance
Construction products will be classified according to the performance characteristics of load-bearing capacity R, integrity E and insulation I, as required in relation to the Commission Decision 2000/367/EC (published May 2000). It details the classification of the resistance to fire performance of construction products, construction works and parts. For some specific product groups, additional performance characteristics may also be required, such as thermal radiation W, self-closing capability C and smoke leakage S.

The new European fire resistance tests are not much different from the fire resistance tests traditionally carried out in furnaces by member states. The primary difference is in the adoption of the plate thermometer that is used to control the temperatures within the fire resistance furnaces.

Differing data
While the plate thermometer was introduced with the expectation that it would reduce discrepancies in test data from furnaces across Europe, it has resulted in a consistent increase in severity of exposure in relation to the UK test furnaces.

This has resulted in a decrease in performance of UK manufactured construction products, which has been demonstrated by the test data that resulted from the Partners in Innovation project.

However, the fire resistance of a construction product may only be declared in accordance with the Commission Decision 2000/367/EC. Therefore, the European supplement has been drafted to comply with the Commission Decision and its resulting limitations, but at the same time not compromise the current levels of fire safety.

This has meant that the fire resistance times currently specified in Appendix A of Approved Document B have been maintained in the draft European supplement. This will clearly equate to an increased level of safety in fire resistance terms, but due to the plate thermometer and the Commission Decision, equivalence is not possible.

The concept of a modified 30 minute standard of fire resistance is not possible within the context of the Commission Decision. However, for parts of buildings where the standard is required it has been accommodated at national level (England and Wales).

This has been done by considering construction products to be deemed to have satisfied the provisions of REI 30, provided that they achieve a load-bearing capacity of at least 30 minutes, and integrity and insulation requirements of at least 15 minutes. In particular, this is specific to some floors, external walls and cavity barriers.

External fire exposure to roofs
Table 3 summarises the standards that will be used when classifying the external fire exposure to roofs within the UK and Europe in the future.

This area has proven to be the most contentious of all. There is little consensus on the appropriate method of test at European level, and this has resulted in the adoption of a three-part method of test. This method will replace the traditional UK test method, BS 476 part 3: 1958.

So far, there has been insufficient data available from the new European tests to enable a decision to be taken on which part of CR 1187 is the most suitable to support the UK regulatory requirements. Information to enable this decision should be available in the near future.

However, due to this uncertainty, no proposal is made in the European Supplement to Approved Document B, on how to use the classifications within the regulatory framework. This is expected to be the subject of a later amendment to the European Supplement.

Further considerations
As more products are tested using the European fire tests, it is inevitable that anomalies additional to those that have already been identified will emerge.

One of the approaches that may be used to deal with such anomalies could be National 'deemed to satisfy' lists. This will mean that if a product, which has been successfully used for a number of years without any known problems related to fire safety, obtains a European classification making it will no longer useable in the UK market place, then the DTLR may give consideration to its inclusion onto a national acceptable list.

Inclusion onto such a list would not be automatic and evidence would be required to demonstrate that the product has not changed in any way, and that a suitable generic description can be provided.

However, such a provision would assist manufacturers during the implementation of the CPD in England and Wales. It would also possibly be open to manufacturers throughout Europe, so as not to present a barrier to trade. This option is unlikely to be available in other member states.