Iingcango zomlilo zihlelwa ngokuhambelana nokumelana nomlilo kwaye zinokwahlulwa zibe: iingcango zomlilo ezikhusela ukushisa (iKlasi A), iingcango zomlilo ze-partial-insulating fire (iKlasi B), kunye neengcango zomlilo ezingenayo i-insulating (iKlasi C). Kukho amabakala amathathu aqhelekileyo okumelana nomlilo kwiingcango zomlilo zokugquma i-thermal: iBakala A (1.5h), iBakala B (1.0h) kunye neBanga C (0.5h).