Emergency Lighting - Fire fighting/protected Stairs

Hi all,

looking for you thoughts and comments on the following.

BS9999 2017 notes that ''normal lighting'' should be maintained in fire fighting shafts. this is noted as being served by a secondary power supply. 

its not very explicit but my question is do you need to maintain the normal lighting LUX levels in fire fighting shafts in emergency conditions i.e failure of the primary supply?

i have reviewed BS5266 and it does not mention this requirement.

also is a fire fighting shaft the same as a fire fighting stair?

BS999 extracts below.

thanks in advance. 

g) Any electrical substation or enclosures containing any distribution board, generator, powered 
smoke control plant, pressurization plant, communication equipment, and any other equipment 
associated with life safety and fire protection systems, should be separated from the building by 
construction with a duration of fire resistance of not less than 2 h.
h) Secondary power supplies should be provided for the following:
1) sprinkler pumps;
2) wet riser pumps;
3) firefighters lifts;
4) fire-fighting shafts (associated equipment and normal lighting);
5) fire-fighting intercommunications installations;
6) pressurization fans (air supply and pressure relief);
7) depressurization fans (air supply and pressure relief);
smoke control system;
 

Also

28 Electrical services
Electrical installations, wiring systems, primary and secondary power supplies for firefighters 
lift installations and any other fire-fighting facilities associated with the fire-fighting shaft 
should be in accordance with both 37.2.3 and the following.
Other lifts in the fire-fighting shaft may be fed from the same primary supply, provided that:
a) the supply is adequate for this purpose; and
b) arrangements are such that a fault occurring in any other lift in the fire-fighting shaft or 
power supplies will not affect in any way the operation of the firefighters lift.
The secondary supply should be of sufficient capacity to:
1) maintain in operation:
•  the firefighters lift and its ancillary equipment;
•  normal lighting and other services within the fire-fighting shaft;