... Flame combustion Average duration of flame for four test samples , s , ≤ 30 3 Duration of flame for any individunl test ... sample , s , ≤45 10 Flameless combustion Average duration of flame for four test samples , s , ≤ 120 - Duration of flame for ... any individunl test sample , s , ≤ 180 - Buming on propane bumer ...