Ray,
Did the smoke alarm have a working 9 volts battery ?
No doubt that you checked that, but just in case.
I installed in not only my own house, but I asked my nieghbours if they wanted permanently wired smoke alarms, I said that you lose protection once the battery runs down, hence the chirping that I've heard when doing the odd domestic job.
Now, they all went for it and I did the install.
I was paid almost nothing, but I didn't do it for the money.
With houses being joined together there is a real risk of inter-house fires occuring if a fire did start in one of the town-houses.
Think of the common roof space and convected heat, add to that tar based building paper.
It's very hard working in a roof space with BA on in a lot of older houses.
Even getting through the Man-hole can be a task.
