Thanks for that Chris.
If i can link photos, ill show you the current state of some of them as i have them in my workshop.
The bar i work in is connected to a restauant and a hotel, so if the fire alarm goes off it will evacuate the full building, so its safe not to use it.
Mind you i work as an electrician and i install fire alarms systems, i might check out the spec of the system and check the sensitivity of the heads. To see if they can cope with fog.