What are the different types of emergency lights?

Emergency Lighting is lighting that automatically illuminates or remains illuminated when the building's power supply is interrupted. The types of lights that fall under this category are exit signs, stand-alone emergency light units, exit signs with integrated emergency lights, and standard general illumination fixtures such as fluorescent 2x4s with integrated battery packs or that are connected to a special emergency circuit that is powered by either a generator or an inverter. (An inverter is a bank of batteries that are charged by the building's power that convert stored battery energy from DC to AC upon activation.) In all cases the emergency illumination must be capable of persisting for a period equal or greater than 90 minutes during emergency mode. The 90 minute required duration is established per the building code. Emergency lighting fixtures are tested to be in compliance with this requirement and will be listed with a certification/testing laboratory such as UL (Underwriters Laboratory), ETL (Intertek), or CSA. It is important to also note that emergency lighting, per the law, must be tested by the building and confirmed to be operable at least once per month, and fully tested once per year.