Illinois air pollution laws live primarily in Title II of the Illinois Environmental Protection Act (415 ILCS 5), not in a standalone state clean air act. The statute works alongside the federal Clean Air Act to set emission limits, require permits for pollution sources, and authorize civil and criminal penalties. Two separate agencies share oversight: the Illinois Environmental Protection Agency (IEPA) handles permits, inspections, and complaints, while the Illinois Pollution Control Board (IPCB) writes the regulations, grants variances, and decides contested enforcement cases.
One feature of the state law catches operators off guard. Section 9 of the Act broadly prohibits anyone from discharging contaminants into the air in a way that causes or tends to cause air pollution, or that violates Pollution Control Board regulations.1Illinois General Assembly. Illinois Environmental Protection Act 5/9 – Acts Prohibited That catch-all goes further than most federal standards, which target specific pollutants at specific thresholds. A facility can comply with every number in its federal permit and still violate Illinois law if its emissions cause air pollution in the state.
Which Agency Handles What
Sending the right request to the right agency saves months. The IEPA is the executive agency. It reviews and issues air permits, inspects facilities, monitors ambient air quality, investigates complaints, and refers cases for enforcement. Permit applications, emissions reports, and pollution complaints all go to the IEPA.
The Pollution Control Board is quasi-legislative and quasi-judicial. It adopts the environmental regulations facilities must follow, grants or denies variances from those regulations, and decides contested enforcement cases. If a facility wants relief from a specific rule, or if a case goes to hearing, the Board decides.
When You Need an Air Permit
Section 9(b) of the Act makes it unlawful to construct, install, or operate equipment capable of causing or contributing to air pollution without an IEPA permit, unless an exemption applies.1Illinois General Assembly. Illinois Environmental Protection Act 5/9 – Acts Prohibited Which permit depends on the size and type of your emissions source.2Illinois Environmental Protection Agency. Air Permits
CAAPP (Title V) Permits for Major Sources
The Clean Air Act Permit Program (CAAPP) is Illinois’s version of the federal Title V operating permit program. It applies to major sources, generally facilities that emit or have the potential to emit 100 tons per year or more of any regulated air pollutant, 10 tons per year of any single hazardous air pollutant, or 25 tons per year of any combination of hazardous air pollutants.3Illinois General Assembly. Illinois Environmental Protection Act 5/39.5 – Clean Air Act Permit Program In ozone nonattainment areas, including parts of the Chicago metro region, the thresholds drop sharply, to as low as 10 or 25 tons per year depending on the severity classification.
CAAPP permits run for five-year terms, consolidate all of a facility’s air pollution requirements into a single document, and are enforceable by the U.S. EPA and by private citizens under the federal Clean Air Act.3Illinois General Assembly. Illinois Environmental Protection Act 5/39.5 – Clean Air Act Permit Program Annual fees scale with allowable emissions: $2,150 for sources under 100 tons per year, $21.50 per ton for sources between 100 and 13,674 tons per year, and a flat $294,000 for the largest emitters above that threshold.4Illinois Environmental Protection Agency. Clean Air Title V
FESOP and Construction Permits
Facilities below the major source thresholds that still need oversight may require a Federally Enforceable State Operating Permit (FESOP). A FESOP caps emissions at levels that keep the facility out of CAAPP, making those caps federally enforceable while avoiding the heavier Title V process. Construction permits are a separate requirement that applies before building or modifying equipment that may emit air contaminants. A facility often needs a construction permit first and an operating permit afterward.
ROSS and Lifetime Permits for the Smallest Sources
The smallest pollution sources may qualify for a lifetime operating permit or for the Registration of Smaller Sources (ROSS) program. ROSS replaces a full permit with an annual registration for sources that emit less than 5 tons per year of combined criteria pollutants, less than 0.5 tons per year of combined hazardous air pollutants, and less than 0.05 tons per year of lead or mercury.5Cornell Law Institute. Illinois Admin Code Title 35, 201.175 – Registration of Smaller Sources Registered sources must still comply with every applicable statute and regulation; ROSS only removes the full application and renewal cycle.
Penalties for Violations
Illinois penalties are higher than many operators expect. Under Section 42(a) of the Act, any violation can draw a civil penalty of up to $100,000 plus up to $25,000 for each day the violation continues. For CAAPP-specific violations, including permit term violations, failure to allow inspections, or noncompliance with fee or filing requirements, the penalty is up to $25,000 per day.6Illinois General Assembly. Illinois Environmental Protection Act 5/42 – Civil Penalties
Starting July 1, 2026, those maximum amounts will be adjusted annually based on the consumer price index.6Illinois General Assembly. Illinois Environmental Protection Act 5/42 – Civil Penalties Beyond fines, the IEPA can seek injunctive relief compelling a facility to install additional controls, modify operations, or shut down until it comes into compliance. Knowing or willful violations can also trigger criminal penalties.
Facilities that discover their own violations may qualify for reduced or eliminated gravity-based penalties under the federal EPA’s Audit Policy if the violation is self-disclosed in writing within 21 days of discovery and corrected within 60 days, among other conditions. The violation cannot have caused serious actual harm or presented an imminent danger, and the same or closely related violation cannot have occurred at the facility within the prior three years.7U.S. Environmental Protection Agency. EPA’s Audit Policy
When Equipment Fails: Malfunction, Breakdown, and Startup
The defenses available when equipment fails are narrower than operators often assume. Under 35 Illinois Administrative Code Section 201.149, continued operation during a malfunction or breakdown that causes an emission violation is prohibited unless the facility’s current operating permit specifically authorizes it.8Cornell Law Institute. Illinois Admin Code Title 35, 201.149 – Operation During Malfunction, Breakdown or Startups The same rule governs emission exceedances during startup: without permit coverage, the exceedance is a violation.
Advance permission can be built into a permit, but the standards are strict. For malfunction or breakdown, the facility must show that continued operation is necessary to prevent injury to people or severe damage to equipment, or that operations are required to provide essential services. Keeping production running for economic reasons alone will not qualify. For startup emissions, the facility must demonstrate that all reasonable efforts have been made to minimize startup emissions, the duration of individual startups, and the frequency of startups.
When permit authorization is in place and the facility fully complies with its terms, that creates a prima facie defense to enforcement. The defense depends on securing the permission before the event, not after, and on prompt reporting and thorough documentation.
Variances from Board Regulations
When compliance with a Board regulation would impose an arbitrary or unreasonable hardship, a facility can petition the Pollution Control Board for a variance under Section 35 of the Act.9Illinois General Assembly. Illinois Environmental Protection Act 5/35 – Variances The Board must issue a written opinion explaining its reasoning. The IEPA can also grant provisional variances for short-term hardship situations.
Variances are not blanket exemptions. They are time-limited, carry conditions, and must be consistent with federal law. A variance from an Illinois Board regulation cannot authorize a violation of the federal Clean Air Act or its implementing regulations. The fact that a regulatory standard is under review and compliance is expensive does not, by itself, establish the required hardship.
How Residents Report Pollution or Sue a Violator
Illinois residents concerned about air pollution from a nearby facility have more than one option. The most accessible is a pollution complaint filed directly with the IEPA, which can be submitted electronically through the agency’s website, by mail, or by fax. For ongoing problems like persistent odors or dust, the IEPA may ask the complainant to keep a log of incidents using template forms the agency provides.10Illinois Environmental Protection Agency. Pollution Complaint Environmental emergencies should be reported immediately to the Illinois Emergency Management Agency at 1-800-782-7860.
Illinois law also gives private citizens a direct enforcement tool. Under Section 31(d) of the Act, any person can file a formal complaint with the Pollution Control Board against anyone allegedly violating the Act, its regulations, a permit, or a Board order.11Illinois General Assembly. Illinois Environmental Protection Act 5/31 – Citizen Enforcement Unless the Board finds the complaint duplicative or frivolous, it will schedule a hearing. The complainant must serve a copy on the alleged violator immediately. This state mechanism does not require the 60-day waiting period that applies to federal citizen suits.
Federal citizen suits under Section 304 of the Clean Air Act are a separate route. Any person can sue an alleged violator of an emission standard or limitation in federal district court, but must first provide 60 days’ written notice to the EPA, the state, and the alleged violator.12Office of the Law Revision Counsel. 42 U.S. Code 7604 – Citizen Suits If the EPA or the state begins its own enforcement action during that 60-day window, the citizen suit is generally barred, though the citizen can intervene in the government’s case as a matter of right.