Q: What’s the difference between primary fire and supplemental fire? Do I need both?
A: Primary fire requirements have changed over the years, and will vary based on the year the house was built and/or last time it had construction done. Primary fire is required by the state and is not optional. Once installed, it cannot be removed from the house without the AHJ (Authority Having Jurisdiction [town building department/fire official normally]) authorizing it. Primary fire can be either a high voltage system (120v) or low voltage (12/24).
In today’s terms (2019 simplified), “Primary Fire” is a smoke detector in every bedroom, outside of every sleeping area within 21 feet, and 1 per level of the dwelling including the basement.