a glow - in - the - dark marking pen that is intended for use for marking structures during search and rescue operations , particularly during a fire , is herein disclosed . the glow - in - the - dark properties of the ink are activated by breaking an inner glass tube contained within the plastic marker body and shaking it . the cap is removed and the pen can be used upon various surfaces as needed . the glow - in - the - dark ability of the ink allows others to see writing in diminished lighting environments , such as emergency personnel who wish to alert other personnel that a room of a structure is being checked or has been checked .