Halon 1301 Extinguishing System 6517 sign points out that people are within a hazardous area. It also provides clear instructions on what a person would need to do before entering an area.
The sign must be prominently displayed for all to see, to advise them on what should be done if the system discharges or they hear an alarm. The sign will indicate that people should not re-enter an area until it has been ventilated.
Fixing requires anything as simple as sticky pads, 'No-nails' type adhesive or double-sided tape.