Reaction to fire
National Class: Historically products were tested to BS 476-6 and 7 and then classified as Class 0, Class 1 etc dependant on their performance.
Reaction to fire national classes have now been removed from Approved Document B for England & Wales (2019 edition).
European Class: Products should now be classified to European Class A1, A2 etc. under EN 13501-1.
Resistance to fire
National Class: BS 476-20 is a furnace test to prove fire resistance performance in terms of integrity (E) and insulation (I) in minutes.
For example, a product may achieve 120 minutes integrity and 90 minutes insulation.
European Class: Products should be tested to the relevant EN standard such as EN 1364-4 or EN 1366-4. The fire resistance in terms of integrity and insulation is then classified to EN 13501-2.
For example, a product may achieve 120 minutes integrity (E 120) and 90 minutes insulation (I 90), this would receive a classification of EI 90.
Approved Document B for England & Wales (2019 edition) now lists classification to EN 13501-2 as the primary route to compliance. BS 476-20 is listed as an alternate route to compliance.