I have noticed that the typical LED light bulbs I buy at the home improvement store are marked “NOT FOR EMERGENCY LIGHTING” and sometimes have “OR EXIT SIGNS” added at the end. Plain old incandescent filament light bulbs do not have that marking. Why can’t an LED light bulb be used for emergency lighting or in an EXIT sign? Are they less reliable?
There are LED bulbs specifically intended for use with battery powered emergency lighting. I think they are just indicating those are not that type of bulb.
The LED bulbs have the exact same base as their incandescent counterparts that also operate at 120 Volts AC. Would the emergency lighting systems switch to a 120 volt DC battery source to keep the lights glowing? If so, I can see where an incandescent bulb would work just fine with a DC source whereas the electronics in the LED bulb would not.
Typical LED bulbs are picky about the voltage. If it goes too low (not unusual during an emergency), they do not produce light. It’s also why many LED bulbs are marked “not for dimmer switches”.
But LED bulbs can be designed for low voltage and dimmer switches. Read the packaging and instructions carefully.
It’s not going to be 120 volts, but with incandescents current makes a lot more difference than voltage, so high current 6 or 12 volt batteries would work (as an example). The LED bulbs are trying to convert 120VAC into much lower voltage DC, not requiring much current, and that converter isn’t going to work over a wide range of voltages in bulbs intended to replace incandescents for regular lighting at the lowest cost.
The LED so marked may not be instant on. And may be effected if the power is not 60 Hz and 120 Vac.