Stephen Harris Staff Engineer at UL UK, introduces the standard testing requirements for reaction to fire of building products, looks at what can influence fire test performance and examines the added value that independent third-party certification offers those who specify products for the built environment.
Stephen Harris, Staff Engineer, UL
Fire in buildings puts the safety of occupants at risk, either directly, by exposure to the fire conditions, or indirectly, as a result of the response of the building to exposure to fire. Potential responses of the building that could represent a risk to life safety include:
- Ease of ignition, resulting in early involvement
- High rates of heat release
- Rapid spread of fire on surfaces (walls and ceiling linings)
- Production of excessive volumes of smoke
- Behaviours, such as melting and particles/flaming droplets
- Excessive heat flames and smoke flow through fire separating elements of structure
- Excessive distortion of the structure – rendering the building unsafe
- Total or partial collapse of the structure due to fire weakening the structure
What does reaction-to-fire testing involve?
Reaction-to-fire testing measures the contribution of a material or system to fire, at the early stages of a fire (the first five points detailed above), as this is crucial to the safe evacuation of a building. European tests differ in methodology from the older British standard tests. There are some equipment differences, and in particular the test result classification, are different. The European tests classifying the smoke release performance of a product and also the number of particles/flaming droplets the product produces. Both of these are key elements in the risks that a product poses when involved in the early stages of a fire.
Regardless of the test method, all test results specifically relate to the performance of the specimen of the product under the particular conditions of test, i.e. test results provide a guide to the potential fire performance of a product and may not reflect the exact performance of the product under real fire conditions. However, it is a benchmark and offers a standard by which to compare products and their likely performance in a building.
The United Kingdom Accreditation Service (UKAS) accredits laboratories to test, measure, and evaluate the physical properties of materials, and components. Laboratory accreditation is carried out against the internationally recognised standard ISO/IEC 17025 to assess factors relevant to a laboratory’s ability to produce precise, accurate tests and data. These factors include:
- Technical competence of staff
- Validity and appropriateness of test methods
- Suitability and maintenance of test equipment
- Testing environment
- Sampling
- Handling and transportation of test items
- Quality assurance of test data
European testing is conducted on construction products and building elements including rubber, plastics, paper, and wood, using standardised test equipment methods.
BS EN 13501-1 provides the reaction to fire classification procedure for all construction products, including products incorporated within building elements. Products are considered in relation to their end use application. BS EN 13501-1 separates these types of products into three categories, which are:
- Floorings
- Linear pipe thermal insulation products
- Construction products, excluding floorings and linear pipe thermal insulation products
Classification is achieved via one or a combination of tests.
Classification of European Test Results
BS EN 13501-1 is the fire classification specified in each of the product standards that enable products to be categorised, as required by The Construction Products Regulation.
The classification is split into three parts, the main classification, the smoke classification and the flaming droplet classification.
- The main part of the classification is its letter – A1, A2, B, C, D, E and F. A1 (non-combustible) is the highest level of performance, with F the lowest performance level (no performance determined). Flooring materials and linear pipe thermal insulation products are classified according to the same classes A1, A2, B, C, D, E and F followed by the abbreviation ‘fl’ for flooring and ‘L’ for linear pipe thermal insulation products. Products classified in A1 and A2 classes are non-combustible materials and from B to F are combustible materials in ascending order.
- There is a suffix smoke classification of s1, s2 or s3. s1 is the best level of performance and s3 is the worst performance level. There are no smoke requirements for Class E products.
- There is also a suffix classification for particles/flaming droplets of d0, d1 or d2. d0 is the best level of performance and d2 is the worst performance level. There is no flaming droplet requirement for floorings.
Many construction products that have achieved a test classification can be CE marked (or UKCA marked from 2023). The CE mark by itself does not necessarily indicate that the product is suitable for the end application. It will indicate a set of performances against specific criteria through the manufacturers Declaration of Performance, which will accompany the product when sold. One of those declarations will be the fire performance classification. However, it is essential to check that the product’s performance is suitable for the end use application.
British Standards vs European standards
There is no direct comparison between British Standards tests and European Standards tests results. Therefore, a product that passes a British test and has been classified under the national system cannot be regarded as equivalent to a particular European test result. However, it is generally accepted that a European test classification can be regarded as the equivalent to the British test result. This assurance of equivalence is a result of historic research testing completed at accredited UK test laboratories. Because of the complexities of the European test, the way in which results are calculated, plus the additional smoke and flaming droplet suffixes for the European tests; the BS results cannot be compared in the same reciprocal way.
Until the revision in 2019, UK Building Regulations listed both British and European types of tests as suitable evidence of performance and it specifies the required classification of materials for specific areas within the building. However, EN performance is now the required reaction to fire performance classification. Some products may still be legitimately in the marketplace with only a British classification. However, Approved Document B should be consulted prior to specification use and acceptance from building control.
Influencing factors in differences from testing to onsite fire performance
Many different products and system properties can influence the fire performance of a product and any variation from that which was tested to that which is installed onsite can mean the products performance could be significantly worse than the indicated test classification.
These include:
- Substrate used for testing – The three standard substrates used in testing are plasterboard, calcium silicate board and fibre cement board. Cement board is the densest of the three and represents brick or cement walls in the end use application. Calcium silicate is less dense than fibre cement board but has a greater density than plasterboard. All three are classed as A2 – s1, d0 substrates. However denser materials normally have a better heat sink than less dense materials. This means that more of the heat from the test flames goes into heating up the substrate and therefore anything attached won’t heat up to ignition temperature quite so quickly and during the test more heat will be absorbed by the substrate. i.e., the product could perform better on a test by just changing the substrate. This will of course be reflected on the test report, but often the test reports are not supplied by the manufacturer.
- Fire retardants – It isn’t always a question of the more the better, particularly for the European tests which have a measure of the smoke produced, and fire retardants normally contribute to greater smoke production. Test specimens can be sent in by the test sponsor directly to the test laboratory. The sponsor will need to declare the formula to the test laboratory and provide the fire-retardant details; including the percentage of retardant in the product and the type used. Without the checks and balances that the third-party certification process adds to the testing process i.e., production control audits, audit sample selection, ongoing surveillance and monitoring of product labelling etc., there is a significant element of trust in the manufacturers ethical approach to the consumer.
- Mechanical fixing or adhesion to the substrate – If a product is not as securely fixed or adhered to a substrate in the onsite application as it was in the test, the material may detach from the wall which can expose more of the material to the fire attack.
- Air gaps – Either within a product or between the product and the substrate, airflow through vertical gaps does influence the fire performance of a system on the test rig. Just like a chimney drawing air to through in a domestic chimney. The more air and therefore oxygen the fiercer the flames. If on site for example a different profile is used, or the air gaps are larger than that which was tested the performance in a fire could differ significantly.
- Product colour – Colour can also influence performance; light colours can reflect heat whilst darker colours can absorb heat. Colours such as red and dark yellow can have more organic content in their pigments thus adding fuel to the product. It is not always possible to tell which product colour will perform worse and products with multiple colour variations should have test evidence to support the colour variations.
- Weight or density – Weight or density of a material can also have an impact on fire performance. A denser product could be harder to heat to the point of combustion thus delaying the contribution of the product to fire growth. A different weight of wallpaper for example which might only mean a few added micrograms to the weight per metre squared but it could add on a significant percentage of fuel to the overall product.
- Thickness – The amount of fuel available to burn increases with thickness and this may mean a 10mm product gains one classification, but the 20mm product crosses the grade boundary.
- Application rate – Application rate can also have an impact on product performance. Too much being applied can increase the fire load. Too little being applied in the case of fire-retardant varnish, for example, may reduce the actual fire protection performance on site.
- Adhesives – The type of adhesives used to bond products to a substrate can also be a factor in fire performance. The amount used, the application rate, is it spot applied, or brush applied, and what type of adhesive is used when there are alternatives available. These can all factor into the end performance. The type of adhesive used, and the application rate and method should be clearly indicated on test and certification evidence.
The importance of third-party certification
In the UK, the Department for Business, Energy and Industrial Strategy (BEIS) supports the use of conformity assessment through accredited certification bodies.
“Conformity assessment and accreditation are important parts of the nation’s quality infrastructure”
“Conformity assessment is the demonstration that what is being supplied actually meets the requirements specified or claimed”
“Conformity assessment is thus an indispensable part of the nation’s business, technology and quality infrastructure”
Third-party certification means that a UKAS accredited independent organisation has, for example, reviewed the manufacturing process of a product and has independently determined that the final product complies with specific standards for safety, quality, or performance. This review typically includes comprehensive formulation/material reviews, testing and facility inspections. Most certified products bear the certifier’s mark on their packaging to help consumers and other buyers make educated purchasing decisions.
Product certification schemes will also typically have continued annual audit of the factory of production to ensure the product remains the same as that which was tested and can include sample testing requirements to ensure the reaction to fire performance of the product remains the same.
READ: Why FIREX International is fully committing to third-party certification in 2022 and beyond
Fire test reports are normally difficult to obtain from manufacturers for their products and they are not normally supplied with manufacturers own product specification details. The fire performance is normally declared in the supporting literature. With a certificated product however, the information about the product is publicly available from the certification bodies website, which details the test configuration, including substates and adhesive type/application rates, test results/classification and any range of variations covered. So, if a wall covering achieves an EN Classification of B s1 d0, for all colours and in three different weights. The consumer can be assured that if the product as supplied fits those parameters when purchased, its fire performance is covered by the certification.
As another example, of why third-party certification offers assurance above those of a single test report, the amount of resin is a key factor in the fire performance of mineral wool insulation products. Too much resin will add to the amount of organic combustible material within the product, which will add to the products combustibility. During the factory audit, the auditor from the certification body will examine the results of the internal tests carried out at the factory. They will be able to check what happened to non-conforming products i.e., those with too much resin added. In addition, they will check the type of resin and the tests done to ensure the resin is consistent with that which was included in the tested samples. Samples of the product will also be purchased from the supply chain and retested independently, to see if the same results are achieved.
About the author
Stephen has over 24 years’ experience in fire testing and certification. He has a fire engineering degree from UCLAN and understands why reaction to fire is so important in the built environment. Working out of UL’s U.K. office, he manages European testing carried out at UL’s ‘Centre of Excellence for Fire-Testing Laboratory in Rosenheim, Germany.
Get in touch with UL for further information, here.