It is not only the building, but the occupancy that must be considered. What is happening in the building? Has that changed? Remember that Part 2 of the OFC requires the CFO to classify a building based on its major occupancy in conformance with the building code.
If the installation was prior to a building code then the minimum would be the Part 9 of the OFC depending again on the occupancy. If Part 9 does not apply because of the building design one would have to review the associated risk and issue an Inspection Order based on some reasonable/logical measure.
Monitoring realistically is based on size, occupancy and occupant load, all risk factors. So, if the shoe fits…
Audibility is actually a good example. Current OBC requirements have a minimum level of audibility. Fire alarms installed prior to these requirements have been successfully upgraded by Inspection Order throughout the Province. The technical guideline is just a reasonable/logical measure.
Now my head hurts! Thanks for making me think!