Larissa

Thanks for the reminder, we have some linked to our security system and I need to get the whole thing serviced.
As for battery ones, write the date you changed your battery in permanent marker on the side of the alarm, then change it each year, vacuum outside once in a while to remove dust. You also need to bear in mind positioning, I think gable celings are a no no as you get areas of "dead" air - it doesn't circulate as much.