Group C: Flammable gas, flammable liquid produced vapor, or combustible liquid produced vapor mixed with air that may burn or explode, having either a maximum experimental safe gap (MESG) value greater than 0. 45 mm and less than or equal to 0. 75 mm, or a minimum igniting current ratio (MIC ratio) greater than 0. 40 and less than or equal to 0. 80. Note: A typical Class I, Group C material is ethylene