Class0，达到BS 476-7的Class1 和 BS 476-6 Pi<12, Si<6
16. The highest National product performance classification for lining materials is Class 0. This is achieved if a material or the surface of a composite product is either:
composed throughout of materials of limited combustibility; or
a Class 1 material which has a fire propagation index (I) of not more than 12 and sub-index (i1) of not more than 6.
Note: Class 0 is not a classification identified in any British Standard test.
来自英国建筑防火法规，Document B，Building Regulations 2006，Technical Guidance Document B
Approved Document B (fire safety) volume 1: dwellinghouses, 2006 edition incorporating amendments up to December 2018