# Delaware — State Residential Radon Disclosure, Testing, and Certification Requirements

For Delaware, disclosure required is Yes; sellers of property containing up to four residential dwelling units must disclose information about radon tests or inspections. Sellers must also provide purchasers with written information about radon developed by the state; testing mandated is Yes; child care centers and homes must present evidence that the facility is free of radon hazards prior to licensing, with testing once every five years; professional certification required is No state-specific licensing requirement for radon professionals; action level pci l is 4.0 pCi/L; school testing required is No, recorded from its source on 2026-08-15.

- **jurisdiction:** Delaware
- **disclosure required:** Yes; sellers of property containing up to four residential dwelling units must disclose information about radon tests or inspections. Sellers must also provide purchasers with written information about radon developed by the state. _(verified: appears in the quote below)_
- **testing mandated:** Yes; child care centers and homes must present evidence that the facility is free of radon hazards prior to licensing, with testing once every five years.
- **professional certification required:** No state-specific licensing requirement for radon professionals
- **action level pci l:** 4.0 pCi/L
- **school testing required:** No
- **statute citation:** Delaware Code, tit. 6, §§ 2570--2578; Delaware Code, tit. 14, § 3003a

## What the source says

> Requires sellers of property containing up to four residential dwelling units to disclose to the buyer, agent and/or subagent all known material defects of the property, including information about radon tests or inspections. Sellers must also provide purchasers with written information about radon developed by the state.

## Source

- https://www.eli.org/sites/default/files/files-pdf/2025%20Radon.pdf

Last verified: 2026-08-15. Review by: 2027-08-15.
Part of [State Residential Radon Disclosure, Testing, and Certification Requirements](https://referencesource.org/state-radon-disclosure-requirements/).