Smoke and Carbon Monoxide Detectors

The first week of October was fire prevention week, I’m a little late to the party but I wanted to talk about Smoke Detectors, Carbon Monoxide detectors and the current requirements for placement in the home. Almost every home I inspect has incorrectly installed smoke detectors, or none at all.

The placement of smoke detectors has changed in years past, at one point the requirement was only that there was one per floor, like other things these rules have changed. For the purposes of this post I will be using current building standards as a guide as specified in SPS 321.09.


As of this writing smoke alarms are required:

  • Inside of each sleeping room
  • On floors that contain one or more sleeping rooms, alarms are required to contain a smoke alarm outside of the sleeping rooms, within 21 feet of the door centerline of any sleeping room, an must be in the exit path from a sleeping room.
  • On floor levels that do not contain a sleeping area, an alarm shall be installed in a common area on each floor level.

In the past smoke alarms were only required within 6 feet of bedrooms, but as you can see here that requirement has gotten more strict over time like many other things. In many homes I inspect I find that people like to attach them to the wall. Since the smoke detector must be as high as possible, one mistake people make is installing their detector too close to the ceiling. As the diagram below shows, the corner of the ceiling and wall intersection must be avoided. Smoke does not gather in this area due to airflow and may cause the alarm to not activate right away.

This image has an empty alt attribute; its file name is Smoke-Detector.png

As a best practice. I like to see the smoke detector on the ceiling about 3 feet into the room. If it is located in the hallway, I like to see them in the center of the hallway width and a minimum of three feet in from the end.

Carbon Monoxide Detectors

Carbon monoxide detectors are required by law in every home in Wisconsin, well, that has been the requirement since the law was enacted in February 2011. The current building code says:

  • Carbon monoxide detectors shall be installed by the owner of the dwelling according to manufacturers specifications.
  • Detectors must be located in basements and on each floor level except for attics, garages, and storage areas.
  • The occupants of the dwelling are required to maintain operating smoke and carbon monoxide detectors.
  • Carbon monoxide detectors shall be placed on each floor of the dwelling.
  • The detector must also be within 21 feet of the centerline of any bedroom door and in the exit path from sleeping rooms.

One little caveat to these rules is that if the home does not have any fuel burning appliance such as a gas furnace or fireplace, or an attached garage, carbon monoxide detectors are not required.

Fire safety is an important issue that many people overlook when buying new homes. Take a minute to check over your home to make sure you are protected. With the holidays on their way it’s a good time to look at other fire hazards associated with that time of year. Check out my holiday safety post here.

As always, I hope you took some value from this post and if you have any home related questions, lease let me know at the email address below.



Aaron M. Zuehlke is the owner and inspector at Zuehlke Inspection Service, LLC, a full-service home inspection company serving Southern Wisconsin. Specializing in Home inspection, Radon Testing, Mold Testing/inspection, Residential Thermal Imaging, and Manufactured Home Foundation Certifications. He also manages several rental properties through Zuehlke Properties, LLC. He can be reached by email at or by calling the office at 608-931-7485.

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