Exit signs – deciding the viewing distance. Emergency exit signs are a mandatory part of building safety. It is essential to maintain the safety of the individuals in your place of business. Evacuation routes must be clearly marked and visible. Any final exits and locations where the escape route may be unclear must have signs installed to reduce uncertainty. However, there are some calculations you need to make when deciding which size of emergency exit sign you need for your premises.
When an inspection of the building is carried out, the fire officer looks to ensure that anyone in the room or corridor can recognise the exit route in an emergency situation. They will walk around the routes and decide where the emergency exits should be. Also the maximum distance somebody could be from it will be assessed. This gives you the maximum viewing distance. The maximum viewing distance deemed safe to be viewed from is given in BS 5266 Pt7/EN1838. You will need to work to these guidelines. Fire exit signs can either be illuminated by an external light source, or have their own internal light source to display the graphics on the signs legend.
Depending which version of sign you use dictates the maximum viewing distance.
Internally Illuminated Exit Sign
The maximum viewing distance is 200 x the panel height.
If the sign is 175mm high then the maximum viewing distance is 35000mm or 35 meters.
175mm x 200 = 35000 mm (35 meters) or 12 inches x 200 = 2400 inches (200 feet).
Externally Illuminated Exit Sign
The maximum viewing distance is 100 x the panel height.
Therefore if the sign is 175mm high then the maximum viewing distance is 17500mm or 17.5 meters.
175mm x 100 = 17500 mm (17.5 meters) or 12 inches x 100 = 1200 inches (100 feet).
In conclusion we know that greater viewing distances are achieved through internally illuminated exit signs. Externally illuminated signs are easy to install but they still need an emergency light to illuminate it during power loss. If you have limited space above an emergency exit door and can only use a smaller sign, but the room is bigger than the viewing distance, then you will need more than one sign to indicate the direction of travel.
If you have any questions or need assistance selecting the exit signs for your premises give our sales team a call