a valve controlled passageway 37 in a secondary fitting 38 which is engaged in the port 21 in the selector valve 14 as heretofore referred to the valve element 39 in the passageway 37 in the secondary fitting 38 is normally closed and is arranged to be actuated by a normally movable button 40 a secondary tube 41 extends from the fitting 32 and communicates with the passageway 33 therein and with a passageway 42 in the secondary fitting 38 which in turn communicates with the interior of the cylindrical body of the selector valve 14 and in the area thereof adjacent the inlet port thereof in order that the cylindrical valve element 28 will normally be in closed relation with respect to the resilient gasket 26 a biasing spring 43 is positioned between a portion of the valve 14 defining the inlet port and an annular shoulder in the adjacent end of the cylindrical valve element 28 a plurality of o ring seals are positioned between the respective parts as will be understood by those skilled in the art the fire protection system disclosed herein is normally energized with respect to the heat sensors 20 and 20a the solenoid valves 17 and 17a are normally closed as are the manually controlled valves 39 in the fittings 38 the main control valve 11 is also closed and the fire extinguishing agent is contained in the replaceable cylinder 10 upon one of the heat sensors 20 or 20a detecting a fire or an abnormal rise of temperature in the supervised area the signal originated by the sensor travels back through the appropriate circuits and opens the selector valve 14 or 14a which.