Table 1: Flame classification [27].

ClassificationSpread of flame at 1.5 mins Final spread of flame 
Limit (mm)Limit for one specimen (mm)Limit (mm)Limit for one specimen (mm)

Class 1165165 + 25165165 + 25Very low rate
Class 2215215 + 25455455 + 45Low rate
Class 3265265 + 25710710 + 75Medium rate
Class 4Exceeding the limits for class 3Rapid rate