therein generally the known gassing device includes a vertically stationary metering cylinder 10 and a filling head 12 which is vertically translatable with respect thereto a spool 14 which has a throughgoing longitudinal channel an enlarged upper sealed portion and can adapter located at its bottom interconnects metering cylinder 10 and filling head 12 metering cylinder 10 encloses a ported internal sleeve 16 a ported retainer 18 and a sliding piston 20 guided by a rod 22 and having a protruding seal 24 on its bottom surface filling head 12 contains a poppet valve 26 which is actuated by raising filling head 12 for example by raising an aerosol container c through use of an elevator table to engage and lift filling head 12 thereby opening poppet valve 26 a conventional aerosol gassing device such as is shown in fig1 and 2 is substantially completely driven by the supply pressure of the propellant as follows with the device in the recovery position shown in fig1 the pressurized propellant is introduced into the interior of cylinder 10 the propellant flows through the ports provided at the top of sleeve 16 to act on the upper surface of piston 20 similalry propellant flows through peripheral ports provided on ported retainer 18 to act with equal pressure on the bottom surface of piston 20 however it will be notd that rod 22 effectively reduces the upper.