For clarity we will start with a quick note that this is not another article about Coronavirus.
It is common for properties to be fitted with fire alarm systems to alert people to a fire and to inform them to evacuate the building. There are a number of different types of alarm system that can be installed depending on the particular circumstances.
While alarms are commonly used to warn people to leave a building there are also circumstances where you may need to warn people of a hazard outside and instruct them to enter or remain in the property, for example a site using chemicals may want to alert persons if there was a spillage of hazardous material. Alternatively a school may want to warn students and staff to stay indoors if an intruder or dangerous dog has been spotted on the premises.
Clearly it would confusion if the fire alarm sounders were also used to warn people to stay in a building, however this does not necessarily mean that an existing fire alarm system could not be used give other warnings provided different sounders were used.
The Fire Industry Association recently published a guidance note on the use of fire alarm systems for giving a lockdown alarm. This guidance, which specifically considers schools, can be downloaded from the FIA website at: https://www.fia.uk.com/static/af80ef9b-128c-41f9-8dd282d05471c3a9/Guidance-Note-Use-of-fire-alarm-systems-for-lockdown-specifically-in-schools.pdf