The short answer to this question is: they should do. However, there are a number of caveats and considerations that could affect your fire alarm’s efficacy.
The secondary power source
The power supply is often one of the first areas impacted in a fire event. This means that all contemporary fire alarm systems are created with a secondary power source. In other words, battery back-up. And this applies to both the individual sounders (alarms) and the central control box of your alarm system. So, in theory, when there is a power outage, these batteries should kick in. Enabling the alarm to sound for long enough for the building to be evacuated.
How do you know if your fire alarm battery back-up is working?
Your fire alarm’s secondary power source can only be relied upon if your fire alarm system is well maintained. British Standard BS 5839-1 dictates that all businesses need to have their smoke detection and alarm systems serviced at least every six months. As well as ensuring that all sensors are functioning fully and there are no electrical faults, this maintenance involves full battery testing and replacement if necessary. Your technician will also ensure that there is no corrosion of the battery. And that the battery fittings are intact. Most fire alarm batteries will need to be replaced every four years to BS5830-1:2017 standard.
However, if you experience a number of power cuts in quick succession – which is potentially possible with the current energy crisis – you may need to replace your batteries more frequently.
Should I test or reset my fire alarm after a power cut?
Contemporary fire alarm systems will usually automatically reset after a power outage. If your fire alarm sounds when the power returns, this is usually a sign that you need to replace the battery back-up. All commercial premises should test their fire alarm system weekly, regardless of power cuts.
The importance of your fire alarm system cannot be overstated. But its value falls dramatically if it does not have efficient battery back-up. Initiating a regular fire alarm servicing schedule is the best way to ensure that your fire alarm is there whenever you need it.