Description of Driving Event:
Following completion of a repair, a work crew laid a hot cotton tar mop on a piece of roofing insulation material on the roof. Although they doused the mop with water, it subsequently ignited spontaneously after approximately two hours and started a fire on the roof. Damage was limited to the mop, the insulation, and a small area of the roof. The undocumented procedure to immerse tar mops in a bucket of water and then lower to the ground after job completion was not performed. To prevent recurrence, the maintenance contractor modified the safety section of the annual roof plan as follows: mops will be disassembled, placed in a sand filled container, lowered to the ground, and disposed of by the environmental support department according to existing regulations. The spontaneous ignition of tar mops is well documented in existing literature, e.g., "Fire Protection Handbook", 17th edition.