As with carbon monoxide alarms, smoke alarm requirements in Minnesota are regularly changing and I recommend following current best practices both for installation and location regardless of the vintage of home you may inhabit.
My recommendation for placement of smoke detectors as a Minnesota Home Inspector may vary from those as required by the state, or the local authority having jurisdiction. I'm not a code inspector, nor do I find when a home being built relevant to its inhabitants safety. So while I always recommend checking with the local authority having jurisdiction on specific requirements, these are my recommendations, and are recommendations only, not requirements.
A Minnesota Home Inspectors recommendations for Smoke Alarms
- Smoke alarms located in each sleeping room.
- Smoke alarms located outside each sleeping room.
- Smoke alarms located on each story, including basements and habitable attics.
- Smoke alarms are recommended to be hardwired, have battery backups, and be interconnected.
- Smoke alarms in rooms with ceiling slopes greater than 1-foot rise per 8 feet horizontally are recommended to be located at the high side of the room.
- A smoke alarm installed in a stairwell is recommended to be located as to ensure that smoke rising in the stairwell cannot be prevented from reaching the alarm by an intervening door or obstruction.
- A smoke alarm installed to detect a fire in the basement is recommended to be located in close proximity to the stairway leading to the floor above.
- Smoke alarms are recommended to be mounted on the ceiling at least 4 inches from a wall or on a wall with the top of the alarm not less than 4 inches, or more than 12 inches, below the ceiling.
- Smoke alarms are recommended not to be located within 3 feet of supply registers of a forced-air heating or cooling system and doors to a kitchen or bathroom containing a tub or shower.
Replacement and Testing Recommendations from a Minnesota Home Inspector
- Replace upon inhabiting a new home.
- Replace every 10 years or sooner.
- Test monthly in addition to manufacturers instructions.
Types of smoke alarms
There are two main types of smoke alarms, ionization and photoelectric and while both alarms have been shown to be effective in detecting fires, some are better under certain circumstances. Ionization smoke alarms are generally more responsive to flaming fires whereas photoelectric smoke alarms are generally more responsive to fires that begin with a long period of smoldering (called “smoldering fires”). If you're interested in the details, I highly recommend visiting the National Fire Protection Associations site which covers this in detail. Because of this difference the Deputy State Fire Marshals recommend the installation of photoelectric smoke alarms near kitchens and locations susceptible to false alarming as they are not as susceptible to these types of false activation.