once the propellant gas now free from liquid particulates exits the coalescing filter 20 it is preferably forced through a first flashback inhibitor 18 the flashback inhibitor 18 is preferably a stainless steel screen which is sufficiently porous to allow uninhibited flow of the propellant gas but prevents the flow of an indicator material into the lower filter chamber 22 of the filter assembly 10 the flashback inhibitor 18 additionally minimizes the ability of an ignited propellant to path or return to the storage drum 30 should the propellant gas accidentally become ignited by an outside source during the filtration process the propellant gas then enters the upper filter chamber 12 which preferably contains activated carbon 32 in this chamber activated carbon 32 adsorbs hydrocarbons from the propellant gas a second flashback inhibitor 14 preferably a stainless steel screen is preferably included within the upper filter chamber 12 to provide additional safety this filter assembly 10 includes a method for determining when it has ceased to function as intended and requires replacement a visual indicator may be in the form of a temperature indicator 34 attached to the upper filter chamber 12 of the filter assembly 10 during proper functioning of the upper filter chamber 12 adsorption of hydrocarbons by the activated carbon 32 causes an increase in temperature of the housing around the upper filter chamber 12 of the filter assembly 10 preferably by having the temperature indicator 34 in direct contact with the upper filter chamber 12 a temperature indicator 34 preferably a liquid crystal indicator is attached to the outer or inner surface.