1. Standard- BS6853 Annex D.8.4
BS6853 Annex D: Methods for measuring smoke density
BS6853:1999 Code of practice for fire precautions in the design and construction of passenger carrying trains.
BS 6853 Annex D.8.4 is utilized for interior and exterior vertical surfaces and horizontal prone surfaces (Tables 2, 3, 5 and 6 of BS 6853: 1999) and seat shell (table 10 of BS6853: 1999).