Carbon monoxide has no smell or color. Map alarms by floor and sleeping area, follow current placement instructions, and check the local rule before a tenant moves in.
A CO alarm hangs beside the furnace, so the move-in checklist says “detector present.” But the bedrooms are upstairs, the attached garage opens near another sleeping room, and no one has checked whether an alarm can be heard there. One device in one mechanical room may leave important parts of the home without the coverage a landlord expected.
Carbon monoxide is colorless and odorless. The U.S. Fire Administration recommends alarms in a central location outside each separate sleeping area and on every level. The CPSC gives similar general placement guidance. Treat an alarm as a planned safety system, not a box to tick because one unit was visible.
Map where people sleep and where exposure can start
Walk the property with a simple floor plan. Mark each separate sleeping area, each level people use, fuel-burning equipment, and the door between the home and any attached garage. The EPA’s current placement infographic also calls attention to rooms over an attached garage and places near the garage entry. A basement bedroom, finished lower level, or converted room can change the questions to ask.
Do not put a unit directly beside a furnace just because that is where the fuel-burning equipment is. EPA’s diagram places alarms at least 15 feet from fuel-burning appliances, and the alarm maker’s instructions may specify suitable locations for that model. Map the locations first, then compare them with the product manual and local requirements. If the directions appear to conflict, ask the local fire or building department before choosing a spot.
Check the actual unit, not just the mounting bracket
For each alarm, record its location, make and model, power source, installation date if known, and replacement date or end-of-life signal. Check that it is powered and unobstructed, then use its test control as the manufacturer directs. The EPA recommends monthly testing. CPSC explains that a test button checks circuitry, not sensor accuracy; it does not replace the unit’s instructions or tell you that an expired sensor is still within its service life.
If you use combination smoke-and-CO alarms, check that the unit is approved for both purposes and located as the manufacturer directs. Smoke and CO are different hazards, and the right location for one function may not answer every placement question for the other. Do not remove an alarm or relocate it to fix nuisance alerts without following the manual and checking code.
Separate safety guidance from the local legal requirement
Federal safety agencies publish recommendations; those pages are not a complete code checklist for every rental. The EPA infographic, updated September 16, 2026, says to follow manufacturer instructions and applicable laws and building codes. The CPSC notes that many state and local jurisdictions require CO alarms and directs consumers to their local building official. Rules can set required alarm types, locations, installation deadlines, and who maintains them; requirements may vary by building type, fuel-burning equipment, sleeping layout, and renovation history.
Before advertising or handing over the keys, check the current rule with the state or local housing, fire, or building authority for that address. Save the source or inspection record you relied on, and ask what applies to a multi-unit building or a converted space. A general federal placement recommendation is a sensible planning aid, but it does not establish that a particular unit meets local law.
Make an alarm sounding an emergency response
Tell residents in writing: if a CO alarm sounds, everyone should go outside to fresh air and call 911 or the fire department. The CPSC says not to look for the source or re-enter until emergency responders give permission. If anyone has a headache, dizziness, nausea, weakness, or confusion, get outside and seek emergency help even if the alarm is quiet. Have a qualified professional check suspected equipment before it is used again.
Your maintenance record can stay simple: a floor plan with alarm locations, model and service-life notes, monthly test entries, the local rule checked, and any repair or replacement still open. That record makes it easier to notice an uncovered sleeping area before it becomes a resident’s problem.
Sources and further guidance
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