During a switching off operation, the moveable contact member moves out of the arcing chamber and quenching gas flows from {HEAD ~ the accumulator space} into the expansion space, through the arcing chamber, {TAIL ~ i.e. the nozzle} 
During a switching off operation , the moveable contact member moves out of the arcing chamber and quenching gas flows from { HEAD ~ the accumulator space } into the expansion space , through the arcing chamber , { TAIL ~ i.e. the nozzle }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL