The placement of exit signs is often a judgment call, and, as a result, there are many misconceptions about where signs should be located and how many are needed.
One misconception is that occupants must always be able to see an exit sign form wherever they are in the building. I have even heard people say that occupants mist always be able to see two exit signs. There is no such requirements in the code. Section 18.104.22.168.2 requires that new exit signs be placed in corridors in such a way that they are visible within 100 feet, but this applies only to new buildings or newly renovated portions of buildings. And the 100-foot spacing only applies in corridors. We expect people to start moving when the fire alarm is activated. Exit signs are needed where the exit, or way to reach the exit is not apparent.
Another question that arises concerns internally or externally illuminated exit signs, either of which is permitted by code. Internally illuminated exit signs are addressed in Section 7.10.7, which requires that internally illuminated signs be listed in accordance with UL 924. Section 7.10.6 addresses externally illuminated signs, which may be made of cardboard, metal, pr plastic and attached to the wall. Such signs may even consist of the word "EXIT" painted on the wall. Since externally illuminated signs are not UL-listed, the code specifies that lettering on the sign must be at least 6 inches high. If an area requires emergency lighting, the exit signs must be visible under emergency lighting conditions. For externally illuminated signs, there must be enough illumination from the emergency lighting to make the exit signs visible and legible. Section -2.9 of the applicable occupancy chapter will help you determine whether emergency lighting is required.
Another mistake people make concerns the requirement for exit sign color. There is no requirement for a specific color! Section 22.214.171.124 simply state that the signs must be of "distinctive color and design that it is readily visible and shall contrast with decorations, interior finish, and other signs."
The "NO EXIT" sign requirements are often misunderstood or misapplied, too. Section 126.96.36.199 states that a "No EXIT" sign is only needed where "any door, passage, or stairway that is neither an exit nor a way of exit access and that is located or arranged so that it is likely to be mistaken for an exit shall be identified by a sign that reads as follows: NO EXIT." This sign is required only if the door does not lead to a way out AND is likely to be mistaken for an exit door. It is not the code's intent that such signs be placed on every door that is not an exit. If the door is labeled as to what it is, such as "Closet, " "Basement," or "Electrical Room," there should be no confusion.
If a "NO EXIT" sign is necessary, Section 188.8.131.52.2 clearly specifies that the word "NO" must be two inches high and the word "EXIT" must be one inch high. This is so occupants will not key in on the word exit and mistake it for an exit sign.
There are a few differences between the exit sign requirements in the Life Safety Code and other codes used outside the United States that might encourage use of pictograms to mark exits or manmade specific color scheme.