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 2 of 10 2.  The primary purpose of a breather on explosion-proof compartment is: Choices: To keep the parts cool To allow harmful gases that cause corrosion to escape To provide inspection openings To let methane out of the compartment