Prohibition signs indicate that an action or activity is not permitted. Its designated symbolic shape is a red circle with a diagonal red slash through it. This is usually superimposed over a black pictograph, e.g. a cigarette, to indicate what specific activity is referred to.
The background is white and any text is black. AS1319 the Australian standards covering safety signage does not specify a required material or nominal size for a sign, but does stress that the type of sign used should be suitable for the intended application, and that employees should be informed of their purpose.
In locations where lighting is good and a sign is mounted in a reasonably prominent position, it is recommended that any symbols be at least 15mm per metre of viewing distance, and any uppercase text be at least 5mm per metre of viewing distance. This should be increased by at least 50% for poor lighting or viewing conditions.
