Replacing some very old mains powered alarms in my house. Currently there is a mains alarm in the downstairs hall and another for the upstairs hall. There’s nothing in the attached garage, kitchen, bedrooms or loft (altho the cabling is easily accessible in the loft so I could add a 3rd alarm there.

So firstly, is the benefit of mains powered just that you don’t need to replace batteries? The battery ones I’ve seen seem to be claiming 10 year battery life so….

Secondly, thermoptek, atom optical, photoelectric, heat sensing – what’s all that about?

Finally, where should I have alarms? I’d guess as a minimum the current locations plus garage and loft. Should I have one on the kitchen? Or will that end up being a “toast ready alert”

heat sensor in the kitchen -toast proof.

the main benifit of using mains is to link them as per regs.

so if your alarm in another part of house goes off all the alarms go off together.

You still have to replace the backup battery in mains units.