Mine Rescue Statements of Fact - Test No. 5 Questions taken from the 2016 Coal Mine Rescue Statements of Fact - Group A Progress Indicator: Question 8 of 20 8.  Within what amount of time of being exposed to air can Class 4 Division 4.2 materials ignite? p. 116 Choices: 10 minutes 20 minutes 5 minutes 15 minutes