(The purpose of emergency lighting is to ensure adequate lighting is provided when the power supply to the normal lighting fails. Emergency lighting is key in making sure people can exit a building safely in the event of an emergency. Emergency lighting illuminates the means of egress which includes stairs, aisles, corridors, ramps, and escalators leading to an exit.)
When we speak of safety or disaster management in general, the emphasis is always on prevention to begin with. To be well prepared at all times to deal with a disaster, if at all it happens, is the first essential need as per any safety manual. The NBC has put down certain guidelines that are non- negotiable to ensure that any enclosed premise is adequately prepared to get all necessary licenses and permissions. Some basics which are recommended for enclosed spaces of all types could be fire alarms, extinguishers, safety signages, illuminated path finding tools and of course, Emergency lights.
An emergency light is a battery-backed lighting device that switches on automatically when a building, apartment or any enclosed space experiences a power outage. Incandescent light bulbs were originally used in emergency lights, before fluorescent lights and later light emitting diodes (LEDs) superseded them in the 21st century. By the nature of the device, an emergency light is designed to come on when the power goes out. The earliest models were incandescent light bulbs which could dimly light an area during a blackout and perhaps provide enough light to solve the power problem or evacuate the building. It was quickly realized, however, that a more focused, brighter, and longer-lasting light was needed. The modern versions provide a high-lumen, wide-coverage light that can illuminate an area quite well. Some lights are halogen, and provide a light source and intensity similar to that of an automatic headlight.
Modern emergency lighting is installed in virtually every commercial and high occupancy residential building. The lights consist of one or more incandescent bulbs or one or more clusters of high-intensity light-emitting diodes (LED). The emergency lighting heads are usually either PAR 36 sealed beams or wedge base lamps. All units have some sort of a device to focus and intensify the light they produce. This can either be in the form of a plastic cover over the fixture, or a reflector placed behind the light source.
Early battery backup systems were huge, dwarfing the size of the lights for which they provided power. The systems normally used lead acid batteries to store a full 120-volt charge. For comparison, an automatic uses a single lead acid battery as part of the ignition system. Simple transistor or relay technology was used to switch on the lights and battery supply in the event of a power failure. The size of these units, as well as the weight and cost, made them relatively rare installations. As technology developed further, the voltage requirements for lights dropped, and subsequently the size of the batteries was reduced as well. Modern lights are only as large as the bulbs themselves - the battery fits quite well in the base of the fixture.
An emergency lighting installation may be either a central standby source such as a bank of lead acid batteries and control gear/chargers supplying slave fittings throughout the building, or may be constructed using self-contained emergency fittings which incorporate the lamp, battery, charger and control equipment. Self-contained emergency lighting fittings may operate in "Maintained" mode (illuminated all the time or controlled by a switch) or "Non Maintained" mode (illuminated only when the normal supply fails).
A commentary on the NBC by G.B.Menon Fire Adviser, Govt. of India {Retd.} Cochin Ex-Chairman CED-22 Fire Fighting Sectional Committee Bureau of Indian Standards. and J.N.Vakil Asst.General Manager{Retd},TAC/GIC,Ahmedabad Ex-Chairman CED-36 Fire Safety Sectional Committee Bureau of Indian Standards mentions emergency lights as an essential commodity in its list. It clearly specifies the following:
1. Emergency Lighting: Lighting provided for use when the supply to the normal lighting fails. 2. Emergency Lighting System: A complete but discrete emergency lighting installation from standby power source to the emergency lighting lamp(s), for example, self-contained emergency luminaire or a circuit from central battery generator connected through wiring to several escape luminaries. 3. Escape Lighting: That part of emergency lighting which is provided to ensure that the escape route is illuminated at all material times (for example, at all times when persons are on the premises), or at times the main lighting is not available, either for the whole building or the escape routes.