Emergency Lighting

This past weekend we had to cancel a symphony concert and evacuate the building due to a power outage caused by a blown transformer. This incident has cause some discussion on the amount of time the emergency lighting is supposed to last. Our current emergency lighting lasts approx. 30 minutes, but during the follow up meetings and such we have been told that by code they are supposed to last 90 minutes. Is there anyone out there that could shine some "light" on this issue so we have a better understanding. Under code how long should emergency lighting last? Thanks in advance.
 
NFPA 101 7.9.2.1* Emergency illumination shall be provided for not less than 1-1/2 hours in the event of failure of normal lighting. Emergency lighting facilities shall be arranged to provide initial illumination that is not less than an average of 10.8 lux (1 ft.-candle) and, at any point , not less than 1.1 lux (0.1 ft.-candle), measured along the path of egress at floor level. Illumination levels shall be permitted to decline to not less than an average of 6.5 lux (0.6 ft.-candle) and, at any point, not less then 6.5 lux (0.06 ft.-candle) at the end of the 1-1/2 hours. A maximum-to-minimum illumination uniformity ratio of 40 to 1 shall not be exceeded.

Your local codes may vary. Your building may be grandfathered if it was built before whichever revision brought this into effect.
 
I'm pretty sure the Life Safety Code requires 90 minutes. As I recall, some lessening of the illumination is permitted, but don't have that at my fingertips. But here it is:

7.9.2 Performance of System.
7.9.2.1 Emergency illumination shall be provided for a minimum
of 11⁄2 hours in the event of failure of normal lighting.
7.9.2.1.1 Emergency lighting facilities shall be arranged to
provide initial illumination that is not less than an average of
1 ft-candle (10.8 lux) and, at any point, not less than 0.1 ft-candle
(1.1 lux), measured along the path of egress at floor level.
7.9.2.1.2 Illumination levels shall be permitted to decline to not
less than an average of 0.6 ft-candle (6.5 lux) and, at any point,
not less than 0.06 ft-candle (0.65 lux) at the end of 11⁄2 hours.
7.9.2.1.3 The maximum-to-minimum illumination shall not
exceed a ratio of 40 to 1.
 
I'm pretty sure the Life Safety Code requires 90 minutes. As I recall, some lessening of the illumination is permitted, but don't have that at my fingertips. But here it is:

7.9.2 Performance of System.
7.9.2.1 Emergency illumination shall be provided for a minimum
of 11⁄2 hours in the event of failure of normal lighting.
7.9.2.1.1 Emergency lighting facilities shall be arranged to
provide initial illumination that is not less than an average of
1 ft-candle (10.8 lux) and, at any point, not less than 0.1 ft-candle
(1.1 lux), measured along the path of egress at floor level.
7.9.2.1.2 Illumination levels shall be permitted to decline to not
less than an average of 0.6 ft-candle (6.5 lux) and, at any point,
not less than 0.06 ft-candle (0.65 lux) at the end of 11⁄2 hours.
7.9.2.1.3 The maximum-to-minimum illumination shall not
exceed a ratio of 40 to 1.

Okay code experts, why 90 minutes? If for evacuation 90 minutes seems way long (even given staff clearing building ect)
 
There are probably minutes of meetings that would tell the real story, but speculating is fun so:
  • Power outages tend to be either under 5 minutes or longer than an hour with very few falling in between. Short outages are resolved through automated schemes and longer outages require a service truck. Maybe 90 minutes covers the majority of outages like fuse replacements and manual breaker reclosures.
  • May 90 minutes is what is typically required for first responders to arrive on the scene and deal with emergencies not directly related to a power outage.
  • Maybe it's related to getting people out of elevators.
 
Not all emergencies are best responded to by evacuation from a structure, or happen such that people are unable to evacuate that structure. Earthquakes, tornadoes, hurricanes, ice storms, blizzards, somebody willfully sabotaging power for the purpose of burglary, terrorism, what-have-you.
 
90 is standard. 2 hours for Chicago; and NYC I think has double the lighting level. You get into telecom and starting seeing 8 hour genny run times, but that's different.
I have personally installed off - the - shelf fixtures that let us work for 4 hours during a flood evacuation... The units were designed for 90 minutes, don't normally drop names but they were Lithonia. Reasonably durable and inexpensive.
 
One thing to remember is that the 90 minutes run time is what should be achieved towards the end of the device's lifespan, anything less and it fails and needs replacement at the next test - so a new battery in good condition should go somewhat longer than 90 mins...

I also suspect the OP's fixtures have batteries that are past replacement time...
 
Not all emergencies are best responded to by evacuation from a structure, or happen such that people are unable to evacuate that structure. Earthquakes, tornadoes, hurricanes, ice storms, blizzards, somebody willfully sabotaging power for the purpose of burglary, terrorism, what-have-you.

Ah yes, the old "shelter in place". That is a very good point. If some natural disaster (or otherwise) has knocked out the power and it is not possible or safe to evacuate, you want ample time to get everyone in to position and have the ability to monitor the situation.
 
We shouldn't forget about emergency responders, who may have to enter a structure after it is evacuated.
 

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