Treatments are listed that can be applied to wood and wood-based products to upgrade their rating for surface spread of flame, by British Standard BS476: Part 7, from Class 3 (occasionally 4) to Class 0. Requirements for Class 0 are described. Treatments for which Class 1 certification has been obtained are also listed under: inorganic salts impregnation treatments, leach resistant treatments, clear surface coatings, and pigmented surface finishes. -- AATA