Safety Moment #96: Safety Signs

The material in this Article is extracted from Chapter 16 (Human Factors and Ergonomics) of the book Plant Design and Operations.

Guidance as to the types of signs and their meanings is provided below.


Prohibition signs mean "You must not" or "Do not do . . ." or "Stop". Signs of this type have a red circle, a white interior and a red bar, as illustrated in Figure 16.4.

Figure 16.4
Prohibition Sign

Prohibition sign

The sign can be supplemented with more specific information, as illustrated in Figure 16.5.

Figure 16.5
Prohibition Sign with Information

Prohibition sign

Other examples of prohibition signs include:

  • No smoking;
  • No open flames;
  • Non-potable water;
  • Do not enter;
  • Do not fish; and
  • Do not use crane for personnel transfer.

Mandatory Action

Mandatory signs mean "You must do . . ." or "Carry out this action" or simply "Obey". They are often used when special PPE (personal protective equipment) is required.

Signs of this type use a blue circle. Figure 16.7 shows that safety gloves are required.

Figure 16.7
Mandatory Sign

Example of a mandatory sign

Other examples of mandatory signs include:

  • Hearing Protection Required;
  • Wash Hands;
  • Chock Wheels;
  • Ground Fuel Truck;
  • Hard Hat Area;
  • Doors Must Be Kept Closed;
  • Goggles Required; and
  • Face Shield Required.


Warning signs are yellow triangles using black lettering, as illustrated in Figure 16.8, which is to do with electrical hazards.

Figure 16.8
Warning Sign

High voltage warning sign

Other examples of warning signs include:

  • H2S Gas;
  • Corrosive Liquids;
  • Radiation;
  • Equipment Automatic Start;
  • Open Trenches;
  • High Temperature;
  • Flammables;
  • Explosives; and
  • Danger High Voltage.

Safe Condition

A green square or rectangle indicates a safe condition, a means of escape or the location of safety equipment, as illustrated in Figure 16.9.

Figure 16.9
Escape Sign

Fire exit safety sign

Other examples of Safe Condition signs include:

  • Emergency Shower Station;
  • Emergency Eyewash Station;
  • Potable water;
  • Emergency Shutdown;
  • First Aid; and
  • Trash.

Fire Safety

A red square or rectangle is to do with fire safety, as shown in Figure 16.10.

Figure 16.10
Fire Sign

Fire exit safety sign

You are welcome to use this Safety Moment in your workplace. But please read Use of Safety Moments.

Copyright © Ian Sutton. 2023. All Rights Reserved.