Mar 29

A reader of the ApartmentAssoc Yahoo Group asks:

Am I correct when I say a 2 story 4 unit building w/ a basement would need 7 co detectors installed.  Can they be combo smoke/co detectors or do we need separate detectors for each function?  Any help would be appreciated…..Thanks

My reply cleaned up a bit from the original is below As of April 1st, 2010 Wisconsin began requiring CO detectors in all multifamily buildings. As of February 1st, 2011 the requirement expanded to all residential buildings including owner occupied single families.  There are a few exceptions such as units that have electric heat AND do not have attached garages AND do not have gas stoves; as well as those with sealed combustion furnaces and water heaters that are inspected regularly.But most WI residential buildings now must have carbon monoxide detectors.

Where to install and how many carbon monoxide detectors are required depends on a number of factors.

The combination smoke detector/CO detector units are okay as long as they are UL listed.  There is no hard and fast rule on how many carbon monoxide detectors are required.  This really depends on the size and configuration of the building. Smart owners will error on the side of too many.

CO Detector requirements for multiunit buildings

Remember that a multiunit building under Wisconsin state code is three units and up in a single structure. In each unit you need one CO detector within 15′ of each bedroom.  So it could be as little as one or as many as the number of bedrooms. (The references in italics are to the Wisconsin Statutes Chapter 101 which can be found here)

§101.149(2)(a)2. Within 15 feet of each sleeping area of a unit that has a fuel-burning appliance. §101.149(2)(a)3. Within 15 feet of each sleeping area of a unit that is immediately adjacent to a unit that has a fuel-burning appliance.

You need at least one in each common hallway.  It could be more if the hallways are over 75′

§101.149(2)(a)5. In each hallway leading from a unit that has a fuel-burning appliance, in a location that is within 75 feet from the unit, except that, if there is no electrical outlet within this distance, the owner shall place the carbon monoxide detector at the closest available electrical outlet in the hallway.

You need at least one in each basement.

§101.149(2)(a)1. In the basement of the building if the basement has a fuel-burning appliance.

You need one within 75′ of any room that has a fuel burning appliance that is not a bedroom.

101.149(2)(a)4. In each room that has a fuel-burning appliance and that is not used as a sleeping area. A carbon monoxide detector shall be installed under this subdivision not more than 75 feet from the fuel-burning appliance.


While at first you may not think this one applies unless you have a wall furnace or space heater, but remember that a gas stove in the kitchen is considered a fuel burning appliance.


CO Detector requirements for One & Two Family

In one and two unit buildings the requirement for CO detectors are a minimum of one per unit and one in the basement.  If the unit is a multilevel then you must have one on each floor The law can be found here, however the important part of the law for most landlords and homeowners  are the following two paragraphs:

“101.647(3)(a) The owner of a dwelling shall install a functional carbon monoxide detector in the basement of the dwelling and on each floor level except the attic, garage, or storage area of each dwelling unit. A carbon monoxide detector wired to the dwelling’s electrical wiring system shall have a backup battery power supply. Except as provided under par. (b), the occupant of the dwelling unit shall maintain any carbon monoxide detector in that unit. This paragraph does not apply to the owner of a dwelling that has no attached garage, no fireplace, and no fuel-burning appliance.”“(b) If any occupant who is not the owner of a dwelling, or any person authorized by state law or by city, village, town, or county ordinance or resolution to exercise powers or duties involving inspection of real or personal property, gives written notice to the owner that the carbon monoxide detector is not functional, the owner shall provide, within 5 days after receipt of that notice, any maintenance necessary to make that carbon monoxide detector functional.”

3 Responses to “Where to install CO detectors”

  1. ARG Enterprises says:

    Do you know if less expensive carbon monoxide detectors that just stick to the wall and change colors if CO detected are allowable?

  2. An outstanding share! I’ve just forwarded this onto a coworker who has been doing a little research on this. And he in fact bought me breakfast because I stumbled upon it for him… lol. So allow me to reword this…. Thanks for the meal!! But yeah, thanks for spending some time to discuss this topic here on your blog.

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