Coal Mine Rescue Field Test 3 Taken from the 2018 NMRA Post 6 Mine Rescue Contest (Day 1) held in Cadiz, OH Progress Indicator: Question 5 of 10 5.  Carbon Monoxide is explosive and flammable.  It’s explosive range in normal air is _________ percent. Choices: 12.0 to 75.0 13.0 to 76.2 12.5 to 74.2 12.5 to 72.4