It is not enough that a safety sign can be seen. It is essential that each sign is quickly understood and that an installation of signs quickly and clearly conveys their intention and continues to confirm the message.
Research has identified that the key requirements for an acceptable safety sign are:-
- Conspicuity: The capacity of a sign to stand out or be distinguishable from its surroundings and thus be readily discovered by the eye. It is the noticeable contrast between a sign and its background, attributed to an exogenous (unplanned) or andogenous (planned) mind-set, with the display having features that attract attention to the sign. Conspicuity is considered a subjective outcome.
- Visibility: The physical attributes of a sign and its contents that allow for detection at a given distance, although legibility may be uncertain. Visibility is considered an objective stimulus.
- Legibility: The physical attributes of a sign that allow for differentiation of its letters, words, numbers, or graphics and that directly relate to an observer’s visual acuity. Legibility is considered an objective stimulus.
- Understandability: That which enables the observer to correctly perceive the information content of letters, numbers or symbols grouped together, or other meaningful relationships on the sign. Understandability is the character of a sign that leads to comprehension of its intended message, and depends on legibility and other considerations of contents and time restraints. It is considered a subjective outcome.
The signs should be positioned so that each sign is always within a readable viewing distance and each sign shall be located so that it is visible to reconfirm the correct route at every intersection or change of direction so that evacuees can move along the escape route quickly and safely. However, in some environments (public buildings, retail areas, etc.) there may be a great number of sign boards, building furniture and visual obstacles that could confuse evacuees in an emergency. This is why safety signs must be easily seen and understood and, in today’s multinational society, it is essential that the meaning of signs does not rely on any specific language.
The Legal Situation
Standardization across Europe was one method of increasing a wider understanding of safety signs. Therefore, the European Community (EC) Safety Signs Directive (92/58/EEC) was published and adopted as ‘The Health and Safety (Signs and Signals) Regulations’ in England during 1996. This piece of legislation set out simple ‘Pictogram’ sign formats to be used within the European Community.
The Regulations showed the intrinsic features required for emergency escape (egress) signs as being white on green, with pictorial symbols of a running man, a direction arrow and a door. These intrinsic features avoided the use of words in any of the escape signs and set out escape route guidance by showing the running man with an arrow down for when the escape route went straight on, arrow right for right turns and arrow left for left turns. The Regulations simplified the vast range of text signs that had previously been used.
The only problem with the EC Safety Signs Directive was that the pictograms supplied were of a different format to those shown in ISO documents and some National Standards such as BS 5499. Here are the three formats currently seen in use in the UK:
- Text only signs (like the common "EXIT" or "SORTE") are not legal and should have already been replaced.
- BS5499 Pictogram signs (with or without supplementary text) are legal but should only have been used when expanding an installation already incorporating similar signs.
- Pictogram only signs with the same format as shown in The Health and Safety (Signs and Signals) Regulations / EC Safety Signs Directive (92/58/EEC) are legal but should not be mixed with other sign formats on any installation.
- From 2012 the new ISO16069 Pictogram signs will also be legal but again should not be mixed with other formats on an installation.
- The latest proposals do not only identify the ISO16069 sign format, there are also references to ISO 3864-1 and ISO 3864-4 to provide detailed information relating to the safety color and contrast color.
- ‘Straight on’ is depicted by an arrow facing up in ISO 16069 (and in BS 5499) whereas the Safety Signs and Signals Regulations do not state which way the arrow should be used.
- ISO 16069 allows the use of supplementary information such as diagonal arrows (for stairs up or down) and in certain instances the use of text (e.g. to distinguish between a normal exit that may also be used for escape and an exit that is perhaps intended only for emergencies and may lead to an exit door that is fitted with a security alarm).
Almost all escape route scenarios can be clearly indicated with the basic ISO 16069 pictogram signs conveying the messages ‘straight on’, ‘go left’, ‘go right’.
The technical features required for these signs are:
- The luminance of any area of safety color of the sign shall be at least 2 cd/m².
- Within either the contrast color white or the safety color, the minimum luminance divided by the maximum luminance shall be greater than 0.2.
- The ratio of the luminance Lcontrast to the luminance Lsafety color shall be not less than 5:1 and not greater than 15:1.
- Signs shall be illuminated to at least 50% of the required luminance within 5 seconds and full required luminance within 60 seconds (this is significantly different from the US standard where the signs must remain continuously illuminated).
However, Local Authorities and Fire Authorities can require new installations to be of either format – EC Safety Signs Directive or ISO 16069 until the situation is resolved by an amendment to the Directive – So check to be sure you are supplying the correct format for your facility.