About this same time, a window at the foot of the stairwell shattered due to the intense heat, giving the smoldering fire a new oxygen supply. This burst of heat also ignited a by roll of material, described by the fire chief in his report as "tarred building paper", stored in the area, which, along with the petroleum-based waxes on the floors, caused the thick, oily black smoke that was believed responsible for so many of the smoke inhalation deaths in the building. The wooden staircase burst into flames and, acting like a chimney, sent hot gases, fire, and very thick, black smoke swirling up the stairwell.