ClearSign Technologies Corporation (the Company) has filed a prospectus supplement to restart its "at the market" offering. The company can offer and sell up to $6,875,000 worth of its common stock. This offering is being conducted under a sales agreement with H.C. Wainwright & Co., LLC, originally dated July 17, 2025. The shares will be issued under the company's existing registration statement on Form S-3, filed on July 17, 2025, and declared effective on July 28, 2025. A legal opinion from Mitchell Silberberg & Knupp LLP regarding the shares has been filed as an exhibit.