For more than half a century, the health risks associated with cigarette smoking have been well documented. Most people are also familiar with the dangers of secondhand smoke, which includes smoke exhaled by a smoker or released from burning tobacco. In recent years, researchers have identified another concern known as thirdhand smoke—the residual nicotine and chemical contamination that can remain on surfaces long after smoking or vaping has stopped.

Beginning in 2026, California law will require greater transparency in real estate transactions involving thirdhand smoke. The Thirdhand Smoke Disclosure Requirement, enacted through Assembly Bill 455 (AB 455), obligates sellers of certain residential properties to disclose any actual knowledge of thirdhand smoke residue or a history of smoking or vaping on the property. Understanding this new disclosure rule is important for both buyers and sellers, as it adds thirdhand smoke to the list of environmental hazards that may affect property value, habitability, and legal liability.

Because this disclosure obligation applies even without visible damage, early awareness of the new requirement can help parties avoid disputes and compliance issues once the law takes effect.

AB 455: Thirdhand Smoke Disclosure Requirement for Sellers

Assembly Bill 455 (AB 455) establishes a new disclosure obligation for California residential real estate transactions beginning January 1, 2026. Under this law, sellers of single-family residential property must provide written disclosure to prospective buyers if they have actual knowledge of thirdhand smoke-related conditions on the property.

Specifically, AB 455 requires disclosure of any known:

• Tobacco or nicotine residue present on the property
• History of smoking or vaping occurring within the property

This requirement applies not only to traditional cigarettes and tobacco products, but also to electronic cigarettes, vaping devices, and other nicotine delivery systems. As a result, properties previously occupied by smokers or vapers may now trigger disclosure obligations even if smoking has long since stopped.

AB 455 effectively expands California’s existing real estate disclosure framework by treating thirdhand smoke as a material environmental condition. The law integrates thirdhand smoke into the disclosure duties imposed under California Civil Code §1102 et seq., placing it alongside other environmental hazards that sellers must disclose when known.

Because AB 455 is based on a seller’s actual knowledge rather than mandatory testing, understanding what information must be disclosed—and when—will be critical for compliance once the law takes effect.

What Counts as “Actual Knowledge” Under the Thirdhand Smoke Disclosure Requirement?

Assembly Bill 455 does not provide a strict definition of “actual knowledge,” but in practice, this standard will likely be interpreted based on what a seller personally knows or has directly observed about smoking or vaping on the property. In California real estate disclosures, actual knowledge generally refers to facts that are known to the seller—not information that requires testing, investigation, or speculation.

For purposes of the thirdhand smoke disclosure requirement, actual knowledge may include:

• Noticeable odors commonly associated with smoking or vaping
• Visible stains, residue, or discoloration on walls, ceilings, carpets, or other surfaces
• Professional testing results indicating the presence of nicotine or tobacco residue
• Personal knowledge of smoking or vaping by current or former occupants

Sellers are required to disclose what they genuinely know, but they are not obligated to conduct inspections, environmental testing, or further investigation to uncover potential thirdhand smoke residue. In practical terms, the standard is straightforward: if a seller is aware of past smoking, vaping, or residue, that information should be disclosed.

Because disputes often arise over what a seller “should have known,” erring on the side of disclosure may reduce the risk of future non-disclosure claims once AB 455 takes effect.

How Is the Thirdhand Smoke Disclosure Requirement Integrated Into Existing Disclosure Forms?

California real estate transactions already require sellers to disclose known environmental hazards and property conditions through standardized disclosure forms, including the Seller Property Questionnaire (SPQ). While the SPQ currently asks about smoking or vaping on the property, AB 455 strengthens and formalizes this obligation by explicitly classifying thirdhand smoke as a disclosure-worthy environmental condition.

Under the new law, thirdhand smoke will be treated similarly to other recognized environmental hazards—such as mold, asbestos, and lead-based paint—when sellers have actual knowledge of its presence or history. This integration ensures that thirdhand smoke disclosure becomes part of California’s established disclosure framework rather than a separate or optional reporting requirement.

To support implementation of AB 455, the Department of Toxic Substances Control is required to update the Homeowners Guide to Environmental Hazards. The revised guide is expected to include:

• An explanation of thirdhand smoke as a common environmental hazard
• Information about its potential health risks and significance
• Methods for mitigation or remediation, where applicable
• Reliable sources for additional guidance and research

By incorporating thirdhand smoke into existing disclosure documents and state guidance, AB 455 aims to standardize seller compliance and improve buyer awareness across California residential transactions.

What Are the Potential Legal Implications of Thirdhand Smoke Non-Disclosure?

As with any required real estate disclosure, a seller’s failure to disclose known thirdhand smoke conditions may expose them to legal liability once AB 455 takes effect. Because the law treats thirdhand smoke as a material environmental condition, courts may view non-disclosure as a serious omission rather than a minor oversight.

If a buyer later discovers tobacco or nicotine residue—or a history of smoking or vaping—that was not disclosed despite the seller’s actual knowledge, the seller could face claims related to non-disclosure. These disputes are likely to arise after escrow closes, particularly when remediation costs or health concerns become apparent.

Common legal claims that may result from a failure to comply with the thirdhand smoke disclosure requirement include:

• Breach of contract, based on inaccurate or incomplete disclosures
• Fraud, where a seller knowingly concealed material information
• Misrepresentation, involving false or misleading statements in disclosure documents

Depending on the circumstances, potential damages may include the cost of remediation, diminution in property value, or other financial losses tied to the undisclosed condition.

As AB 455 becomes effective, courts and litigants may increasingly treat thirdhand smoke non-disclosure similarly to other environmental hazard cases, making compliance especially important for sellers.

What Should Sellers and Buyers Do About Thirdhand Smoke Disclosures?

As California’s thirdhand smoke disclosure requirement approaches, both sellers and buyers can take practical steps to reduce risk and avoid disputes related to non-disclosure.

For Sellers:

Transparency remains the safest and most effective approach. Sellers should disclose any actual knowledge of smoking or vaping on the property, including past use by occupants or visible signs of residue. Even when the impact seems minor, disclosure helps prevent claims that material information was intentionally withheld.

Sellers may also want to review their disclosure forms carefully and consult with a real estate professional or attorney if they are unsure whether certain information should be disclosed under AB 455.

For Buyers:

Buyers should not assume that the absence of visible damage means a property has no smoking history. Asking direct questions about past smoking or vaping, reviewing disclosure forms closely, and remaining alert to odors or residue can help buyers make informed decisions.

In properties where smoking history is disclosed or suspected, buyers may consider hiring a qualified home inspector or environmental professional familiar with thirdhand smoke assessment to better understand potential remediation needs.

Proactive communication on both sides of a transaction can reduce misunderstandings and limit the likelihood of future disclosure-related disputes once the law takes effect.

To learn how disclosure failures are handled in real estate transactions, visit our Non-Disclosure practice area page.

What Does the Thirdhand Smoke Disclosure Requirement Mean Going Forward?

As scientific research continues to highlight the long-term health risks associated with thirdhand smoke, California’s new disclosure requirement reflects a broader effort to promote transparency and informed decision-making in residential real estate transactions. By formally recognizing thirdhand smoke as an environmental hazard, AB 455 adds another layer to the disclosure obligations sellers must consider beginning in 2026.

For sellers, understanding and complying with this requirement may help reduce the risk of future disputes. For buyers, awareness of thirdhand smoke disclosures can provide valuable insight into a property’s history and potential remediation concerns. As with other disclosure laws, early attention to these requirements can help prevent misunderstandings after a transaction has closed.

If a seller fails to disclose known thirdhand smoke conditions, the issue may escalate into a non-disclosure dispute.

How Can Parties Learn More About California Disclosure Obligations?

Understanding and complying with California’s real estate disclosure laws can help prevent disputes after a transaction closes. If questions arise regarding thirdhand smoke disclosures or other material facts, you may wish to consult a non-disclosure attorney to better understand your legal options.

Consult with our Non-Disclosure Attorney in Los Angeles to better understand how these issues are addressed under California law.

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