Mine Gases - No. 13 Questions and answers taken from PowerPoint Presentations found on this site. Progress Indicator: Question 1 of 20 1.  What is the least percentage of methane that can be detected with a flame safety lamp? Although included here, flame safety lamps are no longer in use in coal mines. Choices: Three tenths percent (0.3%). About seventy-five hundredths percent (0.75%). About one percent (1%). Five tenths percent (0.5%).