CO Detectors in Illinois: Owner and Tenant Duties Under 430 ILCS 135

Last verified: February 16, 2026

Illinois carbon monoxide detector laws are anchored in the Carbon Monoxide Alarm Detector Act, 430 ILCS 135. The act applies broadly to covered dwellings, including many rental units, and sets explicit placement, owner, and tenant obligations. It also establishes meaningful criminal exposure for willful noncompliance or tampering, which makes operational discipline important during leasing and maintenance cycles.

In practice, owners and operators should pair statutory requirements with Illinois State Fire Marshal guidance, maintain move-in operability records, document tenant notices and repairs, and audit placement distance during turnovers. Regular internal audits, supervisor spot checks, and quarterly maintenance reviews help confirm unit-level compliance before inspections or legal disputes consistently.

This combination supports legal defensibility, cleaner inspections, and safer residential operations across Illinois portfolios.

Key Takeaways

CO detector requirements for Illinois
Applies to homes?	Yes
Applies to rentals?	Yes
Applies to hotels/STRs?	Not confirmed — check local codes

When Are CO Alarms Required?

Statewide law effective January 1, 2007 (Public Act 94-741).
Exemption may apply for units that (i) do not rely on combustion of fossil fuel for heat/ventilation/hot water, (ii) are not connected to a garage, and (iii) are not sufficiently close to another ventilated CO source, as determined by the local building commissioner.

Where to Install CO Alarms

Within 15 feet of every room used for sleeping purposes (dwelling units and structures with more than one dwelling unit).

For detailed placement guidance beyond legal requirements, see where to place carbon monoxide detectors.

Device Requirements

Must be an 'approved carbon monoxide alarm' that complies with Illinois State Fire Marshal rules, bears a nationally recognized testing laboratory label, and complies with the most recent UL or CSA standards.
May be battery powered, plug-in with battery back-up, or hardwired to AC power with secondary battery back-up.
Combination smoke/CO units are allowed if they comply with applicable requirements and clearly differentiate the hazard.

Landlord and Tenant Responsibilities

Landlord: Owner must supply and install all required CO alarms. Owner must provide one tenant per dwelling unit with written information regarding alarm testing and maintenance, and must ensure batteries are operational at move-in.

Tenant: Tenant must test and provide general maintenance, notify the owner/agent in writing of deficiencies the tenant cannot correct, replace required batteries (except owner ensures operable at move-in), and provide access for repairs.

Responsibility allocation (owner vs tenant) is explicitly stated in 430 ILCS 135/10(c).

Enforcement

Enforced by: Local municipal Authority Having Jurisdiction (AHJ) / local building commissioner (as referenced in the statute and OSFM guidance).

Enforcement typically occurs:

During local inspections where applicable; enforcement may also occur following complaints or incidents.

OSFM guidance notes AHJs may enforce additional local requirements beyond the state act.

Penalties for Non-Compliance

Willful failure to install or maintain required CO alarms is a Class B misdemeanor. Tampering with/removing/destroying/disconnecting alarms or removing batteries (outside inspection/maintenance/replacement) is a Class A misdemeanor for a first conviction and a Class 4 felony for a second or subsequent conviction.

430 ILCS 135/15 (Violation).

Additional Notes

Hotels/short-term rentals are not explicitly named in the statutory definition of 'dwelling unit' shown above; confirm treatment with local AHJ and any local ordinances.

Official Sources & References

Illinois Compiled Statutes — Carbon Monoxide Alarm Detector Act (430 ILCS 135/) — Sec. 5, 10, 15, 20 (state code, accessed 2026-02-16)
Primary statute: definitions (Sec.5), installation/owner-tenant responsibilities (Sec.10), penalties (Sec.15), exemptions (Sec.20).
Office of the Illinois State Fire Marshal — What is CO (Carbon Monoxide)? (Fact Sheet) — Carbon Monoxide Alarm Detector Act overview (agency guidance, accessed 2026-02-16)
OSFM fact sheet noting the act’s effective date and that local AHJs enforce requirements.
Office of the Illinois State Fire Marshal — Carbon Monoxide Detectors (Guidance) — Install within 15 feet of sleeping rooms (agency guidance, accessed 2026-02-16)
OSFM guidance reinforcing the 15-foot sleeping-room proximity requirement and practical placement tips.
430 ILCS 135/10 - Installation and responsibility requirements — Sec. 10 (state code, accessed 2026-02-17)
Direct statutory section covering placement and owner-tenant responsibilities.

Disclaimer: This information is provided for general guidance and is not legal advice. Requirements may vary by city, county, and building type. Always verify current rules with local authorities and official sources.

Frequently Asked Questions

Which Illinois dwellings fall under 430 ILCS 135?

430 ILCS 135 applies to covered dwelling units and requires approved carbon monoxide alarms in locations tied to sleeping areas. The law is not limited to one housing type and is frequently used in both owner-occupied and rental compliance workflows. Illinois State Fire Marshal guidance reinforces the legal baseline and practical placement expectations. Owners should confirm classification for mixed-use properties, but the core rule is that covered residences must maintain operable devices. The safest approach is to treat the statutory language as a minimum standard and add local code checks before occupancy.

How close must Illinois CO alarms be to sleeping rooms?

Illinois placement language in 430 ILCS 135 and related Fire Marshal guidance generally requires alarms within 15 feet of rooms used for sleeping. Device selection must satisfy approved listing standards, and combination smoke and CO units are acceptable when they meet code requirements for both hazards. During inspections, code officials typically look at both distance and operability, not just whether a device exists somewhere in the unit. Property managers should include placement verification in turnover inspections so distance errors are corrected before new occupancy begins.

Who is responsible for maintenance in Illinois rentals?

Illinois divides duties between owner and tenant under 430 ILCS 135. Owners must provide required alarms and ensure operability at move-in, while tenants are expected to perform routine testing, replace batteries where required, and notify the owner of defects they cannot fix. This responsibility split should appear clearly in lease documents and move-in packets. When maintenance records are incomplete, disputes can escalate quickly after incidents. A written policy that tracks notice, repair date, and retesting can significantly reduce compliance risk for both parties.

What penalties apply for CO alarm violations in Illinois?

Illinois treats willful noncompliance seriously under 430 ILCS 135/15. Failure to install or maintain required alarms can be prosecuted as a Class B misdemeanor, while tampering offenses can escalate from a Class A misdemeanor to a Class 4 felony for repeat violations. These are stronger consequences than many states that rely only on civil citations. Because criminal exposure is possible, owners and managers should prioritize prompt repair and documentation after any defect report. Legal anchor citations in compliance files should reference both Section 10 obligations and Section 15 penalties.

In Illinois, when can an all-electric unit still require a CO alarm?

Exemptions can apply in limited scenarios, but Illinois operators should not assume every all-electric unit is outside scope. 430 ILCS 135 includes conditional carve-outs, and local interpretation by the authority having jurisdiction can affect how those exemptions are applied. Buildings connected to garages or adjacent combustion sources may still present risk factors that support alarm installation. Because local enforcement can vary, many compliance teams install alarms in all-electric units as a consistent safety standard unless a clear exemption is documented.

How do Illinois requirements compare with Michigan permit triggers?

Illinois relies on a statewide statutory framework in 430 ILCS 135 with explicit owner-tenant duties and criminal penalty language. Michigan often emphasizes permit-related triggers under MCL 125.1504f and related provisions, which can shift timing and enforcement context. If you manage assets in both states, your compliance checklist should separate statutory duty workflows from permit-trigger workflows. For the Michigan model and cross-reference citations, review Michigan CO detector laws before drafting shared operating procedures.

Practical CO Detector Guides

Beyond legal requirements, these guides help you choose, install, and maintain CO alarms:

Where to place carbon monoxide detectors — room-by-room placement recommendations
CO detector beeping patterns — what different alarms mean
What to do if your detector goes off — emergency response checklist
CO resources and links — official agencies and safety information