SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of report (Date of earliest event reported): July 29, 2021

CLEARSIGN TECHNOLOGIES CORPORATION

(Exact name of registrant as specified in Charter)

12870 Interurban Avenue South

Seattle, Washington 98168

(Address of Principal Executive Offices)

206-673-4848

(Issuer Telephone number)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions (see General Instruction A.2 below).

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

On July 30, 2021, ClearSign Technologies Corporation (the “Company,” “we,” “us” or “our”) announced that Brian G. Fike, the Company’s Chief Financial Officer, Treasurer, and Secretary, dear friend and colleague, passed away. We would like to offer sincere condolences to the family and friends of Mr. Fike.

On July 29, 2021, the board of directors of the Company appointed Colin James Deller, 53, the Company’s Chief Executive Officer and a director, as the Interim Chief Financial Officer (and principal financial and accounting officer), Interim Treasurer, and Interim Secretary of the Company while it pursues the process of retaining a permanent candidate(s) to fill the positions. Mr. Deller will not receive any additional compensation for his service in these interim roles.

Mr. Deller joined us as our President in February 2019, transitioned to the office of Chief Executive Officer on April 1, 2019, and was appointed as a director on February 13, 2020. In 1996, Dr. Deller joined Callidus, where he was employed in Project Engineering and Sales, and over the course of ten years advanced to serve as Chief Combustion Engineer and Manager of Burner Order Execution before being promoted to oversee Callidus’ entire burner business. From 2010 until he left Callidus, following the acquisition of Callidus by Honeywell, Dr. Deller served as General Manager with full profit and loss accountability for the Honeywell UOP Callidus burner business worldwide. During that time, he led his team in developing new international markets, including developing a leading market position in China. From May 2018 until he joined the Company, Dr. Deller served as the interim Global Operations Director for the entire Honeywell International UOP Callidus business, which includes flares and thermal oxidizers in addition to burners.

There were no arrangements or understandings between Mr. Deller and any other person pursuant to which Mr. Deller was selected as an officer. Mr. Deller does not have any family relationships subject to disclosure under Item 401(d) of Regulation S-K or any direct or indirect material interest in any transaction required to be disclosed pursuant to Item 404(a) of Regulation S-K.

On July 30, 2021, the Company issued a press release announcing Mr. Fike’s passing, a copy of which is furnished herewith as Exhibit 99.1.

In accordance with General Instruction B.2. of Form 8-K, the information in this Item 7.01 and in the press release shall not be deemed filed for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall such information be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: July 30, 2021