What is a fire alarm system?
A fire alarm system detects fire and warns occupants through detectors, call points, sounders and a control panel. Its category describes how much of the building is covered, and why.
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</figure>Systems are specified by category rather than by size, and the category follows the purpose: protection of life, protection of property, or both, with coverage ranging from escape routes only to every room in the building.
The panel is the part that gets looked at and the detectors are the part that matters. Most of the system is distributed through the building, which is why servicing covers devices and not only the panel display.
False alarms are a real risk to the system's usefulness. Repeated unwanted signals train occupants to ignore the sounder, and the cause is usually environmental — steam, dust, cooking — rather than a fault in the equipment.
In practice
A system tested weekly from the same call point for a year.
Fifty-two tests, all satisfactory, all from the point by the main entrance.
The rotation is the point: a system tested from one place has proved one place, and the circuits nobody has exercised are the ones that will not work.
The log looks identical either way, which is why the call point reference belongs on it.
What goes wrong in practice
- Detectors covered during building work to stop false alarms, and never uncovered.
- A panel showing a fault for weeks because the fault has become normal.
- Call point tests carried out from the same point every time, so the rest are never proven.