Abstract: An audible alarm activated by a conventional safety valve of a domestic gas cylinder, so as to warn residents of gas being discharged into the atmosphere and contaminating the same; the alarm including a plug on a chamber into which the gas is discharged so that the plug is pushed outward and pull therewith a trigger arm away from a spring wound, toothed gear along whose edge a pivoted lever is bounced up and down so a hammerhead on the lever end strikes a bell.