Although there are no specific codes that favor one style of emergency exit sign over another, installation and design criteria may. Exit sign LED Exit signs that use tritium or photoluminescence are listed and tested the same way as electric exit signs. In some ways, all illuminated exit signs are the same. However, a detailed examination of less visible criteria can assist installers, and building owners make informed decisions that cut overall costs, reduce maintenance requirements, and ensure that signs comply with local legislation. If you're looking to buy or already own an exit sign, chances are it's one of three types: Electric : These signs are connected to a building's electrical supply and illuminated with backup power in the case of a power outage. In addition, they might have emergency lights on the top or sides to help with the evacuation. Photoluminescent : Light-absorbing materials collect light particles and emit them as a greenish slow. These signs have ...