Ten years ago I undertook a large-scale home renovation project on my sixty year-old home. Due to the size of the renovation, building codes required the installation of a whole-house, AC hardwired smoke and carbon monoxide detection system.
My system includes six detectors in total: three smoke-only, and three combination smoke and carbon monoxide.
I’ve discovered a strip of masking tape provides the perfect surface to write a date stamp to indicate an expired battery. This is convenient for households where the chore of changing batteries is done by more than one person.