Carl Thompson, Technical Manager for CA Group, addresses the issue.
In the construction and building materials industry, few topics are as critical, and often as misunderstood, as fire performance testing. Two of the most frequently referenced issues in the UK are Fire Resistance and Reaction to Fire. While both address fire safety, they do so from very different perspectives. Understanding these differences is essential for designers, manufacturers, and contractors striving to achieve compliance, safety, and clarity in specification.
Historical Context and Purpose
BS 476 Part 22, first published in 1987, forms part of the long-standing British Standard 476 series, developed to provide methods for assessing how building materials and elements of construction perform under fire conditions. Part 22 specifically deals with “Methods for determination of the fire resistance of non-loadbearing elements of construction” such as doors, shutters, partitions, and cladding assemblies. Its focus is on fire resistance, or how long an element can maintain its integrity and insulation performance when exposed to fire.
BS EN 13501-1, first issued in 2007, is a European harmonised classification system under the Construction Products Regulation (CPR). It does not test materials directly but provides a framework for classifying reaction to fire performance based on results from other specific EN test methods (for example, BS EN ISO 1182, BS EN ISO 1716, BS EN ISO 11925-2 and BS EN 13823). In other words, BS EN 13501-1 addresses how a material reacts to fire, rather than how long it can resist fire.
Much focus is given to Euroclass ratings following the changes in 2019 to Approved Document B for England, and in particular Regulation 7(2) limiting cladding materials to A2 or better for ‘Relevant Buildings’ (high rise residential buildings). This potentially has led to confusion between reaction to fire and fire resistance standards, with the risk of misinterpreting Euroclass ratings as offering a degree of fire resistance.
Reaction vs. Resistance
This distinction between reaction to fire and fire resistance is critical:
- BS 476 Part 22 is concerned with how long an assembly continues to perform its function when subjected to fire exposure. It measures the duration of performance, expressed in minutes (typically multiples of 15 minutes):
– Integrity (E) – the ability to prevent flames and hot gases from passing through
– Insulation (I) – the ability to restrict temperature rise on the unexposed face
A product tested under BS 476 Part 22 might, for instance, be rated as “EI240/15,” indicating 240 minutes Integrity and 15 minutes Insulation fire resistance. Note that BS 476 Part 22 will be replaced in England by BS EN 1364-1 by September 2029, and provides a fire resistance rating for systems in a similar manner.
- BS EN 13501-1 classifies how a material contributes to the development and spread of fire. It focuses on ignitability, flame spread, heat release, smoke production, and flaming droplets. Products are assigned a Euroclass rating from A1 (non-combustible) to F (no performance determined), often accompanied by additional designations such as s1, s2, s3 (for smoke) and d0, d1, d2 (for flaming droplets).
The Move Toward Harmonisation
The adoption of EN standards across Europe (including the UK) aimed to harmonise fire performance classification so that products could be traded freely. In England, BS EN 13501-1 system has become the preferred and most widely recognized classification for most building products, especially following the withdrawal of reaction to fire standards under BS 476 (part 3 and 7) in March 2025. For England BS476-22 is due to be replaced in September 2029 by BS EN 1364-1, continuing the move towards harmonisation (the devolved regions are transitioning at differing speeds).
A comprehensive fire strategy may require both types of testing—reaction to fire (BS EN 13501-1) for materials and finishes, and fire resistance (BS 476 Part 22 or BS EN 1364-1) for doors, partitions, or cladding assemblies. Both standards play vital, complementary roles in ensuring building safety. But to confuse the two very different standards could be dangerous and could lead to incorrect conclusions about product characteristics, or even lead to the incorrect selection of materials based on using the wrong standard for assessing performance.
For professionals specifying materials or designing to code, understanding not only the numbers and letters on a test certificate, but also the philosophy behind them, is key to making informed, life-saving decisions and creating low-risk specified solutions. Reaction to Fire classification cannot be used to demonstrate Fire Resistance, and vici versa.