A flame arrester is a safety device installed on a nozzle on top of a tank when the flash point of the stored product is lower than the possible tank temperature . A majority of the time, a “vent to atmosphere’’ pressure,vacuum valve is installed on top of the flame arrester. A flame arrester is also used as in-line safety device where combustible gases are transported through low pressure pipe lines to actual combustion, as in an incinerator or flare or where combustion fumes are vented through piping to atmosphere where lightning can cause a flame.