Southwest Regional Drager BG4 Exam Taken from the 2019 Southwest Regional Mine Rescue Contest held in Ruidoso, New Mexico Progress Indicator: Question 6 of 30 6.  In some materials, such as oil-soaked rags, heat can accumulate naturally and cause the materials to start burning without being exposed to a flame.  This phenomenon is called: Choices: automatic flare-up spontaneous combustion random eruptive ignition