A fire drill is properly planned in advance. The purpose of a fire drill is twofold. Firstly, it reinforces the fire procedures and training given to staff. A false alarm may well satisfy this objective. However, fire drills also serve the purpose of monitoring the behaviour of staff when the alarm system operates and timing the evacuation. This cannot occur in the event of a false alarm because it occurs without warning, precluding the pre-planning that precedes a fire drill and the monitoring of the drill. After a false alarm, people normally return to work immediately in order to reduce disruption to business. After a fire drill, there should be a debrief with fire wardens and those monitoring the drill, so that any appropriate lessons are learned and fed back into training.
Equally, if there has been a spate of false alarms, it might be appropriate to suspend the next planned fire drill, so avoiding lack of confidence in the fire alarm system and the complacency that arises from constant evacuation.