How long should emergency light batteries last?

[Guest Adam]

hi, is there a maximum time that a emergency light will stay on during a power out?

how long do the batteries last before they go out?
are they industry standard set to 3 hours or more like 12 hours?
thanks

adam

[Tom Sutton]

In accordance with BS 5266-1:2016 Emergency lighting. Code of practice for the emergency lighting of premises, emergency exit lighting can be one or three hours but nowadays it's more than often three hours, because the three hour battery will cover both.

[AnthonyB]

3 hours. 1 hour units haven't been manufactured for years.

[Guest Henry]

as a follow on question when testing emergency lights that are fitted how long does it need to run for before its time for a new battery or unit.  

[Tom Sutton]

Approximately 4 to 5 years subject to a test

[Guest Henry]

thanks thats was about my expected life expectancy of the system. but I was asking how long the run test needs to be to be considered a pass. 

[AnthonyB]

The full rated duration of the fittings - which these days is almost universally 3 hours.