Illinois Radon Testing & Disclosure Requirements — Landlord Compliance Guide (2026)

What is Radon and Why Does Illinois Law Care?

Radon is a naturally occurring radioactive gas that seeps into buildings from soil and rock beneath foundations. The Environmental Protection Agency (EPA) classifies radon as a Class A human carcinogen—the same category as asbestos and tobacco smoke. In Illinois, long-term radon exposure is the second leading cause of lung cancer after smoking.

The Illinois Department of Public Health estimates that roughly 1 in 3 Illinois homes exceed the EPA’s recommended action level of 4 picocuries per liter (pCi/L). Because radon is colorless, odorless, and undetectable without specialized testing, legislatures and regulators treat radon disclosure as a critical habitability issue, not optional property management.

Illinois codified radon disclosure requirements in the Radon Awareness Act (420 ILCS 46), which became effective in the 1980s and has been refined through updates. Unlike some habitability defects (mold, structural damage), radon defies visual inspection. This is why Illinois law places the burden on landlords to affirmatively disclose test results or the absence of testing.

420 ILCS 46: The Legal Framework

Illinois landlords must comply with three overlapping requirements under 420 ILCS 46:

1. Disclosure Before Lease Execution

420 ILCS 46/5 requires landlords to:

• Provide radon information to prospective tenants in writing before they sign a lease or rental agreement.
• Disclose all radon test results conducted on the property within the past 12 months (or available from prior testing).
• Inform tenants whether testing has or has not been performed — silence or omission violates the statute.
• Provide the EPA’s “Consumers Guide to Radon Reduction” or equivalent radon awareness materials in writing.

The statute does not mandate that landlords conduct radon testing. However, it does mandate that landlords disclose whether testing has occurred and what results exist. This distinction is critical: a landlord who has never tested and discloses that fact is compliant; a landlord who has tested and fails to disclose is in violation.

2. Written Lease Acknowledgment

420 ILCS 46/5 requires that the written lease or rental agreement include:

• A specific radon warning statement provided by the Illinois Department of Public Health, OR
• A statement acknowledging that the tenant received radon information and understands radon risks.

The statute provides a model warning form. Landlords are not required to use it verbatim, but the lease must contain language substantially similar to the following:

“RADON GAS: Radon is a radioactive gas that comes from the decay of uranium in soil and rock. It can get trapped in buildings and create health risks from long-term exposure. Testing is the only way to know if radon is present.”

Many landlords fail this requirement by omitting radon language entirely or including only vague references. Illinois courts have upheld tenant claims that missing or inadequate radon warnings render the lease unenforceable or create statutory violations subject to damages.

3. Continuous Disclosure Obligation for Current Tenants

Landlords must disclose new radon test results to current tenants, even mid-lease. If a landlord conducts radon testing after a tenant has moved in, results must be disclosed within a reasonable time. Withholding test results from sitting tenants—for example, delaying disclosure of a test showing radon above 4 pCi/L—can trigger:

• Tenant right to terminate the lease without penalty.
• Rent abatement claims.
• Complaints filed with the Illinois Department of Public Health or state attorney general.

Radon Testing: Not Mandatory, But Practical

Illinois law does not require landlords to test for radon. However, strategic testing protects landlords in several ways:

Why Testing May Protect You

• Demonstrates due diligence: A documented test showing levels below 4 pCi/L proves radon is not a habitability defect, reducing tenant complaints and enforcement risk.
• Prevents tenant-ordered testing costs: If a tenant orders testing after a landlord’s disclosure of “no testing performed,” and results are elevated, tenants may demand the landlord pay for remediation or pursue lease termination. Landlord testing first avoids this surprise.
• Supports lease enforcement: Courts are more likely to enforce leases and evictions if the landlord has proactively disclosed known conditions.
• Reduces liability exposure: If a tenant or their family develops health issues, documentation of low radon levels or proper disclosure strengthens the landlord’s defense in any tort claim.

Testing Standards and Protocols

If you choose to test, Illinois Department of Public Health recommends:

• Use an EPA-certified radon measurement professional. Do not rely on home inspection general radon screens; they are often inaccurate.
• Conduct testing for 48 hours to 7 days using passive (charcoal canister) or active (continuous monitor) devices.
• Test the lowest livable level — typically the basement or lowest occupied room.
• Follow EPA protocols (listed in EPA’s “Radon Measurement Proficiency Program”).
• Keep all test results and certification documents for at least 3 years.

Test costs typically range from $150–$400 per property, significantly less than the cost of defending a tenant complaint or facing lease termination claims.

What Must Be Disclosed to Tenants?

If You Have Tested

Disclose all results in writing, including:

• Test date and location (e.g., “basement, main dwelling”).
• Radon measurement in pCi/L.
• Comparison to EPA action level (4 pCi/L).
• Any remediation steps taken (if results were elevated).
• Name and certification of the testing professional.

Example disclosure:

“A radon test was conducted on [date] in the basement of the property. The result was 2.8 pCi/L, which is below the EPA action level of 4 pCi/L and poses minimal health risk. Testing was performed by [Professional Name], EPA-certified radon measurement professional.”

If You Have Not Tested

Disclose in writing that no radon testing has been performed and provide radon awareness information from the EPA or Illinois Department of Public Health. Example:

“No radon testing has been performed on this property. Radon is a radioactive gas that can accumulate in buildings. Testing is the only way to know radon levels. The tenant may request radon testing at tenant’s expense, or the landlord may agree to conduct testing. Additional information is available from the EPA and Illinois Department of Public Health.”

If Results Exceed 4 pCi/L

If radon levels are at or above 4 pCi/L, you must:

• Disclose immediately in writing.
• Inform tenants of EPA-recommended mitigation strategies (sealing cracks, improving ventilation, installing radon mitigation systems).
• Provide contact information for EPA-certified radon mitigation contractors.
• Clarify whether the landlord will fund remediation or whether the tenant may request lease termination.

Elevated radon can constitute a habitability defect under Illinois common law, even if the lease is silent. Tenants have remedies including rent abatement and lease termination if a landlord fails to remediate or disclose.

Compliance Checklist for Illinois Landlords

Use this checklist to ensure compliance with 420 ILCS 46:

Compliance Task	Deadline / Timing	Documentation	Responsibility
Conduct or obtain radon test results	Before first tenant move-in (optional, but recommended)	Test report with date, location, result (pCi/L), tester name	Landlord or certified professional
Write radon disclosure (if tested or not tested)	Before lease execution	Written disclosure letter or lease addendum	Landlord
Provide EPA radon information	Before lease execution	Copy of “Consumers Guide to Radon Reduction” or equivalent	Landlord
Include radon warning in lease	Before lease execution	Signed lease with radon warning language	Landlord
Obtain tenant acknowledgment / signature	Before lease execution	Signed disclosure or lease with date and tenant initials	Landlord (secure signatures)
File or maintain records	Ongoing; retain 3+ years	All disclosures, test reports, tenant signed acknowledgments	Landlord
Disclose new test results to current tenants	Within reasonable time after testing	Written notice with test results and date	Landlord
Remediate (if results ≥4 pCi/L)	Within reasonable time; vary by lease terms	Mitigation contractor reports, follow-up test results	Landlord (if obligated by lease)

Penalties and Legal Consequences for Non-Compliance

Statutory Violations Under 420 ILCS 46

Failure to comply with radon disclosure requirements can result in:

• Lease voidability: Tenants can terminate leases without penalty if radon information was not disclosed before lease execution. Unlike some habitability defects, tenants do not need to prove harm; the omission itself is violation.
• Statutory damages: While 420 ILCS 46 does not specify a damage amount, courts have awarded damages based on breach of statutory duty and implied covenant of habitability. Typical awards range from $500–$5,000 for failure to disclose, plus attorney fees.
• Rent abatement: Tenants in properties with elevated radon can demand rent abatement if the landlord fails to remediate or disclose. Some Illinois courts have upheld abatement of 25–50% of rent until radon is mitigated.
• Attorney fees: Prevailing tenants can recover attorney fees from landlords in radon cases, particularly if the violation was knowing or reckless.

Regulatory Enforcement

The Illinois Department of Public Health enforces radon disclosure requirements. Enforcement actions include:

• Complaint investigations: Tenants can file complaints with the Department of Public Health. The agency investigates and may issue citations.
• Cease-and-desist orders: Persistent violations can result in cease-and-desist orders prohibiting property rental until compliance is achieved.
• Administrative fines: While 420 ILCS 46 does not specify fine amounts, the Department of Public Health can pursue penalties under general administrative law (typically $500–$2,000 per violation).
• License or registration suspension: If your state requires property management licensing, radon violations can be grounds for suspension or revocation.

Common Law Habitability Claims

Beyond statutory violations, elevated radon can support habitability claims under the Illinois Residential Tenants Rights Act (765 ILCS 742). Tenants can assert that radon above EPA action levels renders a property uninhabitable and pursue:

• Repair and deduct remedies (tenant pays for mitigation, deducts from rent).
• Constructive eviction claims (abandonment and damages).
• Breach of implied warranty of habitability (lawsuit against landlord).

These claims can result in damages significantly exceeding statutory penalties.

Multi-Unit Properties: Higher Stakes

Landlords with 2–75 units face elevated scrutiny because radon in one unit can affect adjacent units. Illinois enforces stricter disclosure requirements for multi-unit properties:

• Building-level disclosure: If radon testing has been performed anywhere in the building, results must be disclosed to all prospective tenants, not just those in the tested unit.
• Unit-specific testing: Radon levels can vary significantly between units. Testing should occur in units being rented or soon to be rented, or the landlord should disclose that unit-specific testing has not been performed.
• Common area mitigation: If radon levels are elevated, mitigation may require ventilation or sealing in common areas, which creates cross-unit compliance burdens.
• Inspection access: Tenants in multi-unit buildings have stronger rights to request radon inspection access, and landlords cannot deny access without creating presumptive violations.

For self-managing landlords with 2+ units, robust record-keeping and proactive testing are essential liability controls.

Remediation Options and Landlord Obligations

EPA-Recommended Mitigation Methods

If radon levels exceed 4 pCi/L, the EPA recommends:

• Sub-slab depressurization: Installing a PVC pipe through the foundation to vent radon directly to the roof (most effective; costs $800–$2,500).
• Caulking and sealing: Sealing foundation cracks and gaps (low-cost, $100–$500; limited effectiveness alone).
• Improved ventilation: Installing exhaust fans or increasing air exchange (moderate cost, $200–$1,000).
• Drainage improvements: Installing perimeter drains or sump pumps to reduce soil moisture (cost varies; $500–$3,000).

Who Pays for Mitigation?

Illinois law does not explicitly assign remediation costs. Instead, it depends on:

• Lease terms: The lease may specify that the landlord is responsible for radon remediation. If the lease is silent, courts apply implied habitability obligations.
• Common law habitability: Courts have held that landlords must remediate radon if levels are substantially above EPA action levels, treating it as a habitability defect. Tenants can repair-and-deduct if landlords refuse.
• Tenant choice: If radon is disclosed and documented, some leases allow tenants to elect lease termination rather than wait for remediation. Landlords can negotiate this language.

Best practice: Include explicit language in your lease addressing radon:

“If radon testing reveals levels at or above 4 pCi/L after lease execution, the landlord will [remediate at landlord’s expense / offer lease termination / share remediation costs]. Tenants may not unilaterally withhold rent for radon-related concerns without following the notice and cure procedures in this lease.”

Post-Remediation Testing

After mitigation, conduct a follow-up radon test to confirm effectiveness (typically 7–30 days post-remediation). Disclose follow-up results to tenants. If levels remain elevated, further mitigation is required.

Real-World Compliance Scenarios

Scenario 1: New Lease, No Prior Testing

Situation: You are renting a 3-unit building for the first time. No radon testing has been performed.

Compliance steps:

1. Decide whether to test. (Recommended: test at least one unit to establish baseline.)
2. If not testing, write a disclosure: “No radon testing has been performed. The tenant may request testing or the landlord may arrange testing.”
3. Provide EPA radon guidance document in writing.
4. Include radon warning language in lease.
5. Obtain tenant signature acknowledging receipt of radon information.
6. Retain all documents for 3+ years.

Outcome: Compliant. The lease is enforceable, and you have documented disclosure.

Scenario 2: Testing Reveals 6.2 pCi/L

Situation: A radon test on your 2-unit property shows 6.2 pCi/L in the basement (above 4 pCi/L action level). Unit 1 is currently occupied; Unit 2 is vacant and ready to lease.

Compliance steps:

1. Immediately disclose the result to the current tenant in Unit 1 in writing, including a copy of the test report.
2. Notify the tenant that radon levels are above EPA action level and explain health risks.
3. Offer remediation options or lease termination (depending on your lease and preference).
4. Engage an EPA-certified radon mitigation contractor to install sub-slab depressurization or equivalent.
5. Conduct follow-up testing 7–30 days after remediation.
6. Before leasing Unit 2, disclose the original test result (6.2 pCi/L), the mitigation work completed, and the follow-up result (e.g., 2.1 pCi/L post-mitigation).
7. Provide radon warning in Unit 2 lease and obtain tenant signature.
8. Document all communications and test reports.

Outcome: Compliant. You have disclosed known conditions and taken reasonable steps to remediate. The follow-up test protects you from future claims.

Scenario 3: Tenant Requests Testing; Results Are Low

Situation: A tenant in your property requests radon testing at their expense. The test returns 1.8 pCi/L (below action level).

Compliance steps:

1. Obtain a copy of the test report from the tenant (or hire your own certified professional if the tenant’s test is questionable).
2. Disclose results in writing to the tenant: “Testing conducted [date] shows 1.8 pCi/L, below EPA action level.”
3. Document that you have disclosed the result.
4. If you lease to a new tenant afterward, disclose the prior test result and explain it was below action level.

Outcome: Compliant. Low radon results are favorable and should be prominently disclosed to future tenants to support leasing.

Frequently Asked Questions

Q1: Is radon testing mandatory in Illinois?

A: No. 420 ILCS 46 does not require landlords to conduct radon testing. However, it requires landlords to disclose whether testing has been performed and what results exist. Tenants can request testing, but landlords are not obligated to conduct it unless the lease specifies otherwise. Best practice is to test at least once to establish baseline conditions and reduce liability exposure.

Q2: What happens if I sign a lease without including radon warning language?

A: The lease may be voidable at the tenant’s election under 420 ILCS 46. Tenants can terminate without penalty, and you will have no legal recourse if the tenant claims they were not informed of radon risks. Additionally, the tenant could pursue damages for statutory violation. Always include radon warning language in all residential leases.

Q3: I did not disclose radon to my current tenant. Can I disclose now?

A: Disclosing now is better than not disclosing, but it does not cure the original violation. The tenant may have a claim for breach of statutory duty and may have grounds to terminate the lease retroactively. Consult an attorney and consider offering a rent abatement or lease modification to resolve potential disputes. Going forward, ensure all new leases include proper radon disclosures.

Q4: If I remediate radon, do I need to test again?

A: Yes. Follow-up testing 7–30 days after mitigation is essential to confirm that the radon level has decreased below 4 pCi/L. If follow-up testing shows levels remain elevated, additional mitigation is required. Disclose follow-up results to tenants. This documentation protects you from future habitability claims.

Q5: What if a tenant refuses to sign the lease with radon warning language?

A: The tenant’s refusal does not waive your obligation to provide radon information. Document that you offered radon disclosure, explain it in writing, and note the tenant’s refusal. Some landlords use email confirmations or certified mail. However, refusal to sign may be grounds to decline to lease to that tenant. You have no obligation to lease to a tenant who refuses to acknowledge statutory disclosures.

Integrating Radon Compliance into Your Leasing Workflow

Self-managing landlords often juggle multiple compliance requirements. To simplify radon compliance:

• Create a radon disclosure template specific to each property. Include property address, test date (if tested), result (if tested), EPA action level reference, and signature block.
• Maintain a radon testing schedule. Test new properties before first occupancy. Re-test every 3–5 years or when major foundation work is done (cracks repaired, etc.).
• Store all test reports and disclosures digitally. Use cloud storage or your lease management system to ensure 3+ year retention and quick retrieval in case of tenant disputes or enforcement inquiries.
• Include radon questions in pre-lease tenant communications. Ask if the tenant has radon concerns or has experienced radon issues in prior residences. This opens dialogue and demonstrates landlord diligence.
• Standardize lease language. Use the same radon warning and remediation-cost-allocation language across all your properties (unless specific local rules differ).

Platforms like LeaseBase Lease Operations can centralize lease templates and ensure radon language is consistently included before tenants sign. This eliminates the risk of omitting radon warnings on individual leases.

Staying Current with Illinois Radon Law

Illinois radon law is not static. The Illinois Department of Public Health regularly updates guidance on radon testing standards and remediation. Recent trends include:

• EPA update (2023): The EPA lowered its recommendation to focus on radon levels above 2.7 pCi/L as a potential health concern, though 4 pCi/L remains the official action level. Illinois has not yet adopted the lower standard in statute, but courts may reference EPA guidance in habitability disputes. Monitor for legislative updates.
• Green remediation focus: Radon mitigation is increasingly viewed as a property improvement (not just a repair). Some state tax incentives exist for homeowners who install mitigation; landlords should investigate whether rent increases or tax deductions apply.
• Digital disclosure standards: Illinois is gradually moving toward digital lease delivery. Ensure your radon disclosure language works in digital formats and that e-signatures are properly captured.

Subscribe to Illinois Secretary of State updates and the Department of Public Health’s radon guidance page to stay informed of changes.

Documenting Radon Compliance: A Retention Strategy

Documentation is your defense. Retain:

• All radon test reports with certified professional’s name, license, test date, location, and result.
• Copies of radon disclosures provided to tenants (dated and signed or initialed by tenant).
• EPA guidance documents or Illinois Department of Public Health radon awareness materials provided to tenants.
• Signed leases with radon warning language.
• Email confirmations if disclosures were provided electronically.
• Mitigation contractor reports and follow-up test results (if remediation was performed).
• Tenant communications regarding radon concerns or requests for testing.

Retention period: 3 years minimum after lease termination (to cover most tenant claims and statute of limitations). Seven years is safer if you have capacity.

If a tenant or enforcement agency challenges your compliance, these documents prove you acted in good faith and followed Illinois law.

Key Takeaway: Radon Disclosure is Non-Negotiable

Radon is the second leading cause of lung cancer in the United States. Illinois takes radon disclosure seriously because the gas is invisible and dangerous. Unlike some landlord-tenant disputes that hinge on subjective judgments (e.g., “Is the unit habitable?”), radon violations are clear-cut: either you disclosed or you did not.

For self-managing landlords with 2–75 units, radon compliance is a baseline requirement, not an optional extra. The cost of disclosing and (if prudent) testing is trivial compared to the risk of lease terminations, rent abatement claims, statutory damages, attorney fees, and regulatory enforcement.

Action steps:

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