Abstract: A device for alerting miners of an unsafe condition existing in mine shafts includes a surface-engaging member, a chamber-defining member having a compressible medium therein, and a plunger connected between the surface-engaging member and chamber-defining member. The plunger is slidably engaged with the chamber at one end in contact with the compressible medium therein so that the plunger moves in response to a compression force applied to the surface engaging member and applies pressure on the compressible medium. A switch for actuating an alarm in response to a predetermined amount of movement between the surface-engaging member and the chamber-defining member, is provided and a visual indicator operatively associated with the compressible medium is utilized so as to set the switch to establish the predetermined amount of movement necessary to actuate the alarm.