The Fire Alarm (ZF5) safety sign has a red ringing alarm on the square shaped safety sign
 
The alarm symbol indicates where the fire alarm can be located in the event of an emergency and is often used in conjunction with one of the following safety signs:
Location Of Fire Fighting Sign
Location Of Fire Fighting Sign (Diagonal)
The fire alarm safety sign is also available as a Photoluminescent (glow in the dark) sign as a single safety sign or as a combination of more than one safety sign.
Refer to the Photoluminescent section for various combination options. 
SABS standard safety sign