I used to live in Germany where smoke detectors where mandatory at some point. It was also the landlords responsibility. So what you had was a some company coming into your home once a year to check all the smoke detectors. I found that to be very intrusive.

Not sure of this process has been digitised since (in Germany probably not), but I don’t really miss it. (I live in Switzerland now, and here smoke detectors are not required by anyone (might depend on Canton)).