Which buildings are covered
The Wisconsin Department of Safety and Professional Services states that multi-unit residential buildings of three or more units with fuel-burning appliances must have carbon monoxide detectors. DSPS lists covered occupancies including hotels and motels, condominiums, apartments, dormitories, fraternities and sororities, convents and seminaries, jails and prisons, homeless shelters, community-based residential facilities, tourist rooming houses and bed and breakfast establishments. Hospitals and nursing homes are excluded.
One- and two-family dwellings fall under separate rules that the DSPS page above does not cover. If you own a single-family home or a duplex, confirm the current requirement with your municipal building inspector rather than assuming the multi-unit rules apply to you.
Where detectors go
Placement depends on where the appliance is, per the administrative rule DSPS cites (SPS 362.0915):
- Appliance inside the unit, such as a gas range: a detector is required in that unit, near the sleeping room.
- Appliance outside the unit, such as a shared gas fireplace: no detector is required inside the unit if one is installed on the ceiling between the appliance and the unit.
- Forced-air furnace: a detector is required in the first room or area served by each main duct leaving the furnace, plus either alarm signals transmitted to all served units and a staffed monitoring location with fire department notification, or a detector in every fourth unit on the same floor.
- No combustion appliances in the unit at all: no detector required.
The underlying statute, Wis. Stat. s. 101.149, puts detectors in a unit "outside of each separate sleeping area in the immediate vicinity of the sleeping rooms," and requires one inside a sleeping room that contains a fuel-burning appliance or has an attached bathroom containing one.
The owner's duties
Owners must install detectors according to the manufacturer's instructions and use only devices bearing a UL listing mark or a comparable independent certification mark. Detectors must be reasonably maintained per the manufacturer's instructions.
The deadline worth memorizing: when an occupant gives written notice that a detector is non-functional, or was removed by someone other than the occupant, the owner must repair or replace it within five days of receiving that notice. The same five-day window applies after written notice from a certified inspector.
Tampering carries real penalties. Under the statute, removing, disconnecting or taking the batteries out of an installed detector, outside of inspection, maintenance or replacement, is punishable by a fine of up to $10,000, up to nine months' imprisonment, or both for a first offense, with a second offense classified as a Class I felony. Uncorrected violations found on inspection carry a $50 per day forfeiture.
This is a plain-language summary of published state guidance, not legal advice. Rules change and municipalities can be stricter. Confirm specifics with your local building inspector.
Sources
Every figure above comes from one of these. Where they disagree, the post says so rather than averaging them into a single number.