of fluid through the valve between an inlet pipe a and an outlet pipe b a similar annular lip 46 at the opening of the bore 37 into the chamber 24 provides a stop against which the flow control element 22 rests in its 34 open 34 position not shown and in that position the spring 26 presses against the element 22 with sufficient force to assure fluid tight contact between that element and the lip 46 the valve 10 preferably is disposed vertically as illustrated with the support plate 30 below the seat body 18 whereby gravity assists the spring 26 in urging the flow control element 22 toward the lip 46 since the valve 10 is intended to remain in its illustrated closed condition thereby preventing flow from the pipe a to the pipe b until the ambient temperature rises to a dangerous level the choice of the composition of the fusible spacers 34 depends upon what that temperature level is for the particular installation and upon the melting point of the composition accordingly the valve 10 can be tailored to suit a wide variety of uses by merely selecting the appropriate fusible composition for the spacers 34 as should be apparent from the foregoing so long as the fusible spacers 34 are intact the compression element 36 exerts a force upon the flow control element 22 greater than that of the spring 26.