jokar, why does the test need to be done for the night staff? Surely the pupose of the test is to check that the alarm system is working. Now as for a fire drill then yes you must ensure the night staff know what to do, but I can't see the need to test the alarm system for its operation at night.
It is so all members of staff know what the fire alarm sounds like.
However,in the case of care homes it may be better pcratice to rotate the night staff on to one day shift or have the test at a time when all staff can attend (actually,in the case of care homes etc. the fact that most staff work shift patterns makes the same time/same day test a bit unworkable,doesn't it?)
Anyway,in general and from Part 1 Section 44.2 -
b) The weekly test should be carried out at approximately the same time each week; instructions to
occupants should then be that they should report any instance of poor audibility of the fire alarm signal.
c) In premises in which some employees only work during hours other than that at which the fire alarm
system is normally tested, an additional test(s) should be carried out at least once a month to ensure
familiarity of these employees with the fire alarm signal(s).
