Smoke Detectors in existing building NH

[Sean OReilly]

I'm looking at a 3 family building, older home which was converted many years ago. In walking through, one thing that stuck out to me was the absence of hard-wired smoke detectors. The building has no house panel, so installation is going to be expensive any way you look at it.

My question here is are the older battery powered detectors "grandfathered", or will I need to upgrade the detectors immediately. I know the right thing to do is to upgrade the system, but I'm predicting that this could be one of a number of points to be raised during negotiating, and if I say "I'm going to have to install hard-wired smoke detectors with interconnection between units" I want to make sure I'm right.