Fire alarm System Grades relates to the engineering aspects of the fire detection and fire alarm system. Higher Grades of fire system design, tend to provide a greater level of control and monitoring of the system, or greater reliability and availability to perform correctly in the event of fire. The Grade of
fire alarm system that needs to be installed depends on the nature of the property, the level of fire risk and the characteristics of the occupants.
Grade F - fire alarm systems, comprising one or more battery-operated smoke alarms, are the least reliable in the long
term because of the need for battery replacement. For new dwellings, a Grade D system (in which the normal power supply for each smoke alarm is derived from the mains electricity supply and a standby supply is provided) or higher is justified.
However, because of their low cost and ease of installation, Grade F systems (comprising battery-powered
smoke alarms) may be considered for installation in existing dwellings. Their reliability can be improved by
use of batteries that have a long anticipated life and that cannot be removed without the use of a tool.
Nevertheless, Grade F fire detection systems are not appropriate in dwellings in which the fire risk to occupants is high
nor where there cannot be a reasonable certainty that, when the dwelling is occupied, batteries will be replaced within a short time (typically no more than five days) of a battery fault warning indication.
Otherwise, a system in which the normal supply is derived from the mains needs to be used (e.g.
a Grade D
system).
If, in an existing dwelling, a Grade F fire alarm system would be acceptable, it is acceptable to install a Grade E system
(
comprising mains powered smoke alarms). However, if there are likely to be periodic interruptions to the
mains supply, whether due to the inability of the occupier to pay for supplies or due to unreliability of the
mains electricity supply, a Grade D system or higher (in which there is a standby supply)
is then necessary.
Where there is a need for readily accessible control of the fire detection and fire alarm system, a Grade C
system or higher might be provided. Where the fire risk calls for a high standard of system monitoring and
availability, it might be appropriate to install a Grade B system. If the dwelling is very large, or is subdivided into a significant number of dwelling units, a Grade A system is likely to be appropriate.
If the purpose of the system is property protection, fire insurers might require a Grade A system. However, for smaller properties, a Grade B or Grade C system might be sufficient.