A standalone alarm is a single unit that detects and sounds on its own, with no link to any other device. It is the cheapest form of detection and the most widely sold, and it is adequate in a narrower set of situations than the volume of sales suggests. The question is always whether the people who need to hear it will.
Where a single unit is adequate
A single room occupancy where the alarm and the occupant are in the same space. A small open plan unit where one device can be heard everywhere. A supplementary device covering a specific risk in a building that already has a linked system. A temporary arrangement while something better is installed. In each case the sound reaches everybody who needs it.
Where it is a false economy
Any dwelling with more than one storey, where a device downstairs will not wake somebody upstairs behind a closed door. Any property where people sleep. Any building where the route between the device and the occupants passes through a closed fire door, which is precisely what fire doors are for. The cost difference between standalone and radio interlinked units is small against what is being traded away.
Powering and siting
Standalone units are commonly sealed battery devices with a long life cell, which removes the annual battery change and the temptation to borrow the battery. Siting still follows the same rules: on the ceiling, away from corners, away from the kitchen and the bathroom by enough distance to avoid nuisance alarms, and in the circulation space rather than in the room.
Testing and replacement
Test weekly with the button. Replace the whole unit at the end of its stated life, which is typically around a decade from manufacture, because the sensing chamber degrades whether or not the battery is fresh. The manufacture date is on the back and is the figure that matters, not the date it was installed.
Questions people ask about standalone fire alarm
Is a standalone alarm legal in a rented property?
Provision requirements in rented property are expressed in terms of alarms per storey and their working order. Whether standalone units satisfy them depends on the jurisdiction, and Scotland requires interlinking.
Do sealed battery alarms need testing?
Yes, weekly, with the test button. The sealed battery removes the replacement task, not the test.
When should an alarm be replaced?
At the end of the manufacturer's stated life from the date of manufacture, commonly around ten years, regardless of whether it still responds to the test button.