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

For Washington, disclosure required is Yes; sellers of improved and unimproved residential and commercial real property must provide a disclosure statement indicating knowledge of radon gas and other substances of environmental concern; testing mandated is No; professional certification required is No state-specific requirement; action level pci l is No state-specific action level; follows EPA recommended 4 pCi/L; school testing required is No, recorded from its source on 2026-08-15.

- **jurisdiction:** Washington
- **disclosure required:** Yes; sellers of improved and unimproved residential and commercial real property must provide a disclosure statement indicating knowledge of radon gas and other substances of environmental concern. _(verified: appears in the quote below)_
- **testing mandated:** No
- **professional certification required:** No state-specific requirement
- **action level pci l:** No state-specific action level; follows EPA recommended 4 pCi/L
- **school testing required:** No
- **statute citation:** Washington Revised Code §§ 64.06.005--.070, 19.27.074

## What the source says

> Requires sellers of improved and unimproved residential real property, as well as commercial real estate, to provide buyers with a disclosure statement providing information about carbon monoxide alarms and indicating knowledge of substances of environmental concern on the property, including radon gas, formaldehyde, asbestos, and lead-based paint.

## 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/).