TL;DR: Illinois requires a smoke alarm and a carbon monoxide alarm within 15 feet of every bedroom, on every level, and since January 1, 2023 any battery-only smoke alarm that is new, failed, or more than ten years old has to be a sealed 10-year unit. Missing or expired alarms show up in Chicago inspection reports constantly, they are one of the cheapest safety items on the list, and the only real decision is whether the seller replaces them before closing or you do it the day you get the keys.
Most people land on this page because an alarm is chirping at two in the morning. That section is still here, further down. But the people who hire us are under contract on a house or condo in Chicago, and their question is different: does this place have the alarms the law requires, and whose job is it to fix it if not?
What does Illinois actually require for smoke alarms?
The governing statute is the Illinois Smoke Detector Act, 425 ILCS 60/3. Stripped to what matters for a buyer, it says four things.
- Within 15 feet of every bedroom. Every dwelling unit needs at least one approved smoke detector “in an operating condition within 15 feet of every room used for sleeping purposes.” On the ceiling at least 6 inches from any wall, or on a wall 4 to 6 inches below the ceiling.
- Every story, including the basement. Single-family homes need one on every story, “including basements but not including unoccupied attics.” A split level gets one on the upper level unless there is a door between the levels, in which case each level needs its own.
- Multi-unit buildings need one at the top of each interior stairwell. A two-flat, three-flat, or condo building must have a detector “at the uppermost ceiling of each interior stairwell.” That one belongs to the building, not the unit.
- The owner supplies and installs them. Subsection (d) puts installation on the owner. Tenants test and change batteries, but the owner has to make sure the alarms are working the day the tenant moves in.
The 10-year sealed battery rule, and who is exempt
Public Act 100-200 amended the Act effective January 1, 2023. Subsection (e) now says a battery-powered smoke detector must use “a self-contained, non-removable, long-term battery.” That is the sealed 10-year alarm you see on the shelf at any hardware store. The requirement kicks in when a battery-only alarm is newly installed, fails a test, or is more than 10 years from its manufacture date. It does not force you to rip out a working five-year-old 9-volt alarm on the day you close, but the next one you put up has to be sealed.
The exemptions matter in Chicago because so much of the housing stock has hardwired alarms. The sealed-battery rule does not apply to alarms “wired into the structure’s AC power line,” to alarms in a centrally monitored system, or to alarms that use a wireless signal or Wi-Fi to send low-battery notifications. Hardwired alarms with a removable 9-volt backup are legal. A battery-only alarm in a 1920s bungalow that is more than ten years old is not.
Subsection (f) is the one buyers of newer construction should know. Any unit built, reconstructed, or substantially remodeled after December 31, 1987 must have alarms permanently wired to the AC power line, and where more than one is required they must be interconnected so that one triggers all. Units built or remodeled on or after January 1, 2011 must also have battery backup. If a 2015 gut rehab in Logan Square has a single battery alarm stuck to the hallway ceiling, someone skipped a step, and it will be in our report.
What about carbon monoxide alarms?
Separate statute, same distance. The Carbon Monoxide Alarm Detector Act, 430 ILCS 135/10, requires “at least one approved carbon monoxide alarm in an operating condition within 15 feet of every room used for sleeping purposes.” A combination smoke and CO unit satisfies both acts as long as it sounds a different pattern for each hazard. CO alarms may be battery powered, plug-in with battery backup, or hardwired with battery backup. The owner supplies and installs them.
The exemption in Section 20 is narrow: a unit in a building that does not burn fossil fuel for heat, ventilation, or hot water, is not connected to a garage, and is not close enough to another CO source to be at risk. In Chicago that describes almost nothing. A condo with electric baseboard heat but a gas range needs a CO alarm. A high-rise unit with a building boiler and no gas at all may qualify, but the building’s parking garage usually pulls it back in. When in doubt, the alarm is cheaper than the argument.
One more line worth knowing from Section 15 of the same act: removing the batteries from an installed CO alarm, other than to maintain or replace it, is a Class A misdemeanor. We see disconnected CO alarms with the battery door hanging open more often than we should. Sellers do it to stop a chirp and forget. It goes in the report either way.
Does Chicago add anything on top of the state law?
Yes, and the Department of Buildings publishes it in plain language on its smoke alarm and carbon monoxide alarm pages. The additions that change what we write in a Chicago report:
- Built or significantly remodeled in 2018 or later: a smoke alarm is required inside each bedroom as well as outside and within 15 feet of it. Pre-2018 units only need the one outside.
- Apartment and condo buildings: a smoke alarm at the highest level of every shared indoor stairway, consistent with the state act.
- Kitchens and bathrooms: ionization alarms cannot be within 10 feet of a cooking appliance, photoelectric alarms cannot be within 6 feet, and neither type can be within 3 feet of the door to a room with a tub or shower. That open-plan Wicker Park loft with the alarm right over the range is a nuisance-trip waiting to happen, and the City agrees.
- CO alarms in the mechanical room: Chicago requires a CO alarm “in the same room as every fuel-burning furnace, boiler, or hot water heater,” and inside any bedroom that contains a fuel-burning appliance or fireplace. The state act only requires the 15-foot bedroom rule. This is the one that catches condos with a gas fireplace in the primary bedroom and a furnace closet off the hallway.
- Units built since 2018: CO alarms must be hardwired with a removable backup battery. Mount them on a wall at least 5 feet above the floor or on the ceiling.
- The city’s own sealed-battery deadline: Chicago made installation of new removable-battery smoke alarms illegal on January 1, 2023, and requires every remaining one to be gone by January 1, 2033 as they fail or age out. Hardwired alarms with a removable backup are not affected.
If you are buying a two-flat you are buying the stairwell alarm and the boiler-room CO alarm along with the units. If you are buying a condo, those belong to the association, but we still note whether they are there.
What do we write in the report when alarms are missing, expired, or painted over?
Alarms are a safety item, so the finding goes in the summary at the front of the report, not buried in the interior chapter. Three examples from this year, all anonymised.
A River North condo, September 2026. No smoke alarms and no CO alarms anywhere in the unit. Not expired, not disconnected, none. The primary bedroom had a gas fireplace, which under Chicago’s rule needs a CO alarm inside that room on its own. The only alarm in the unit was a round combination smoke and CO unit sitting loose on the plywood ledge behind the tankless water heater, never installed. The finding took one paragraph: no smoke or CO alarms installed; the unit does not meet 425 ILCS 60 or 430 ILCS 135; install sealed 10-year combination alarms within 15 feet of the bedroom, inside the bedroom with the fireplace, and in the mechanical closet before occupancy.
A condo in the northwest suburbs, 2026. Smoke alarm present and painted over, with ceiling paint bridging the vent slots. Paint blocks the chamber that has to admit smoke, so the alarm is written up as not functioning regardless of whether the LED still blinks. The finding: alarm painted over, replace it.
A unit in a two-flat on the Near West Side, 2026. One combination alarm for the whole unit, with a gas furnace and gas water heater on the premises. One alarm can satisfy the 15-foot rule in a small unit. Here it did not reach every bedroom, and nothing covered the mechanical space. The finding cited the 15-foot rule from both acts and Chicago’s mechanical-room CO requirement.
Here is how we get there during the inspection. Every alarm gets the test button. Every alarm comes off its plate so we can read the manufacture date printed on the back, because that date, not the install date, is what the ten-year clock runs from. We look for a UL or other testing-lab label. We check whether hardwired alarms are interconnected by triggering one and listening for the rest. We do not use canned smoke or CO test gas, and the report says so; the test button confirms the horn and the circuit, not the sensor. If the alarm is missing, expired, painted, hanging by its wires, or has its battery door open, it is written up. The scope of what we inspect follows the Illinois Standards of Practice in 68 Ill. Adm. Code 1410.200; alarms are one of the few items where the fix is simpler than the finding.
What do the flashing red light and chirp patterns mean?
If you are at a walkthrough and an alarm is chirping, it is telling you which of the findings above it is about to become. The patterns below are the ones Kidde and First Alert document for their own alarms. Other brands are similar but not identical; when in doubt, the model number on the back of the alarm gets you the manual.
| What you hear or see | What it means | What to do |
|---|---|---|
| Red LED blinks about once a minute, no sound | Normal operation. The alarm has power and is running its self-check. | Nothing. |
| One chirp every 30 to 60 seconds | Low battery on a replaceable-battery alarm. Kidde says the alarm will chirp for at least seven days once this starts. | Replace the battery. If it is a sealed 10-year unit, this is end of life; replace the alarm. |
| One chirp every 30 seconds that continues after a fresh battery | End of life or a sensor error. Kidde states this condition “will not respond to a battery change.” | Replace the alarm. Check the manufacture date; it is almost always past ten years. |
| A chirp between flashes of the red LED | Malfunction (Kidde). | Replace the alarm. |
| Three loud beeps, pause, repeat | Smoke detected. First Alert: “3 Beeps and a Pause: EMERGENCY.” | Get out, then call 911. |
| Four loud beeps, pause, repeat | Carbon monoxide detected. The four-beep pattern is the standard CO signal that distinguishes it from smoke. | Get everyone outside, call 911, do not go back in to open windows. |
| Chirping for several minutes after you pressed the button | Hush mode. Kidde alarms chirp every 30 to 40 seconds for roughly seven minutes while silenced. | Wait it out. If it alarms again, there is smoke. |
Two things people get wrong. A red light by itself is the power indicator on most alarms, not a warning. And a chirp that survives a new battery is not a bad battery; First Alert and Kidde both say to replace every alarm ten years from the manufacture date on the back, and that chirp is the alarm telling you it has reached that date.
Who fixes it before closing, and how hard is it?
Both statutes put installation on the owner, so on paper this is the seller’s item. In practice it is the least contentious repair on any list because of what it costs relative to what it protects. A sealed 10-year combination smoke and CO alarm is an off-the-shelf item at every hardware store in the city. Installing one is two screws into a ceiling or wall and a twist onto the mounting plate. Replacing a hardwired alarm of the same brand is unplugging the harness from the old unit and plugging it into the new one, with the breaker off. Nobody needs a contractor for that.
The exception is when the unit should have hardwired, interconnected alarms and has none: a post-1987 build or a substantial remodel where the wiring was never run. That is electrician work and a legitimate line item in a repair request. We write that finding differently, and we say why in the report so your agent can carry it into the negotiation with the code citation attached.
For everything else, the risk on the other side of the ledger is a fire or a CO event in a home with no warning device. That is not a repair credit conversation. It is a Saturday afternoon and a stepladder.
Seller before closing, or you on move-in day?
Here is the decision, and it only has two branches.
Ask the seller to replace them before closing when the finding involves anything beyond a battery alarm: missing hardwired units, missing interconnection, a dead CO alarm in a unit with gas appliances, or a multi-family building where the stairwell or boiler-room alarm is absent. Put it in the repair request as a safety item with the statute cited, and press the test button yourself at the final walkthrough. Sellers of rental units already owe this under both acts and usually know it.
Do it yourself on move-in day when the finding is expired or missing battery alarms in a home that otherwise passes. Buy sealed 10-year combination units, one within 15 feet of each bedroom, one on each level including the basement, one in the mechanical room, and one inside any bedroom with a gas fireplace. Write the install date on the side in marker. It is faster than the email thread, and you know exactly what is on your ceiling.
Either way, the alarm section of our report will tell you which branch you are on. Our sample report shows how a safety finding is written and where it lands in the summary. If you are buying a unit in a multi-family building, the condo inspection page explains what we cover inside the unit versus what belongs to the association. And you can book online with real-time availability and the price on screen, which most inspection companies in Chicago still do not offer. Reports go out the next business day.