# EDGAR Filing Document

**Accession Number:** 0001434524
**File Stem:** 0001104659-25-112472
**Filing Date:** 2025-11
**Character Count:** 118653
**Document Hash:** a22f8944697d3f359cbfeda970b59be5
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-25-112472.hdr.sgml**: 20251114

**ACCESSION NUMBER**: 0001104659-25-112472

**CONFORMED SUBMISSION TYPE**: 10-Q

**PUBLIC DOCUMENT COUNT**: 67

**CONFORMED PERIOD OF REPORT**: 20250930

**FILED AS OF DATE**: 20251114

**DATE AS OF CHANGE**: 20251114

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** ClearSign Technologies Corp
- **CENTRAL INDEX KEY:** 0001434524
- **STANDARD INDUSTRIAL CLASSIFICATION:** INDUSTRIAL INSTRUMENTS FOR MEASUREMENT, DISPLAY, AND CONTROL [3823]
- **ORGANIZATION NAME:** 08 Industrial Applications and Services
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 10-Q
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-35521
- **FILM NUMBER:** 251485904

**BUSINESS ADDRESS:**
- **STREET 1:** 8023 E. 63RD PLACE, SUITE 101
- **CITY:** TULSA
- **STATE:** OK
- **ZIP:** 74133
- **BUSINESS PHONE:** (918) 236-6461

**MAIL ADDRESS:**
- **STREET 1:** 8023 E. 63RD PLACE, SUITE 101
- **CITY:** TULSA
- **STATE:** OK
- **ZIP:** 74133

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** CLEARSIGN COMBUSTION CORP
- **DATE OF NAME CHANGE:** 20080507

?xml version='1.0' encoding='ASCII'? CLEARSIGN TECHNOLOGIES CORPORATION_September 30, 2025

[**Table of Contents**](#TOC)

------

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

**FORM 10-Q**

**(Mark One)**

**☒** **QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934** 

**For the quarterly period ended September 30, 2025**

**OR**

**☐** **TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934**

**For the transition period from ______________ to _______________**

**Commission File Number: 001-35521**

**CLEARSIGN TECHNOLOGIES CORPORATION**

(Exact name of registrant as specified in its charter)

---

| | |
|:---|:---|
| **Delaware**<br>(State or other jurisdiction of<br>incorporation or organization) | **26-2056298**<br>(I.R.S. Employer<br>Identification No.) |

---

**8023 E. 63rd Place, Suite 101**

**Tulsa, Oklahoma 74133**

(Address of principal executive offices)

(Zip Code)

**(918) 236-6461**

(Registrant's telephone number, including area code)

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

---

| | | | | |
|:---|:---|:---|:---|:---|
| **Title of each class** |  | **Trading Symbol(s)** |  | **Name of each exchange on which registered** |
| **Common Stock** |  | **CLIR** |  | **The Nasdaq Stock Market LLC** |

---

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ⌧ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period than the registrant was required to submit such files). Yes ⌧ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company" and "emerging growth company" in Rule 12b-2 of the Exchange Act.

---

| | |
|:---|:---|
| Large accelerated filer ☐ | Accelerated filer ☐ |
| Non-accelerated filer ⌧ | Smaller reporting company ☒ |
|  | Emerging growth company ☐  |

---

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. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ⌧

As of November 6, 2025, the issuer has 53,273,405 shares of common stock, par value $0.0001, issued and outstanding.

------

[**Table of Contents**](#TOC)

**TABLE OF CONTENTS**

---

| | | |
|:---|:---|:---|
| [PART I](#PARTIFINANCIALINFORMATION_758876) | [FINANCIAL INFORMATION](#PARTIFINANCIALINFORMATION_758876) |  |
| [Item 1.](#ITEM1CONDENSEDCONSOLIDATEDFINANCIALSTATE) | [Financial Statements (unaudited)](#PARTIFINANCIALINFORMATION_758876) |  |
|  | [Condensed Consolidated Balance Sheets as of September 30, 2025 and December 31, 2024](#ConsolidatedBalanceSheets_370122) | 1 |
|  | [Condensed Consolidated Statements of Operations and Comprehensive Loss for the three and nine months ended September 30, 2025 and 2024](#ConsolidatedStatementsofOperations_52792) | 2 |
|  | [Condensed Consolidated Statements of Stockholders' Equity for the three month periods during the nine months ended September 30, 2025 and 2024](#CondensedConsolidatedStatementsofEquity_) | 3 |
|  | [Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2025 and 2024](#ConsolidatedStatementsofCashFlows_17141) | 5 |
|  | [Notes to Condensed Consolidated Financial Statements](#NotestoUnauditedCondensedConsolidatedFin) | 6 |
| [Item 2.](#ITEM2MANAGEMENTSDISCUSSIONANDANALYSISOFF) | [Management's Discussion and Analysis of Financial Conditions and Results of Operations](#ITEM2MANAGEMENTSDISCUSSIONANDANALYSISOFF) | 20 |
| [Item 3.](#ITEM3QUANTITATIVEANDQUALITATIVEDISCLOSUR) | [Quantitative and Qualitative Disclosures About Market Risk](#ITEM3QUANTITATIVEANDQUALITATIVEDISCLOSUR) | 26 |
| [Item 4.](#ITEM4CONTROLSANDPROCEDURES_588585) | [Controls and Procedures](#ITEM4CONTROLSANDPROCEDURES_588585) | 26 |
| [PART II](#PARTIIOTHERINFORMATION_352863) | [OTHER INFORMATION](#PARTIIOTHERINFORMATION_352863) | 27 |
| [Item 1.](#ITEM1LEGALPROCEEDINGS_598160) | [Legal Proceedings](#ITEM1LEGALPROCEEDINGS_598160) | 27 |
| [Item 1A.](#ITEM1ARISKFACTORS_413736) | [Risk Factors](#ITEM1ARISKFACTORS_413736) | 27 |
| [Item 2.](#ITEM2UNREGISTEREDSALESOFEQUITYSECURITIES) | [Unregistered Sales of Equity Securities and Use of Proceeds](#ITEM2UNREGISTEREDSALESOFEQUITYSECURITIES) | 28 |
| [Item 3.](#ITEM3DEFAULTSUPONSENIORSECURITIES_571412) | [Defaults Upon Senior Securities](#ITEM3DEFAULTSUPONSENIORSECURITIES_571412) | 29 |
| [Item 4.](#ITEM4MINESAFETYDISCLOSURES_729119) | [Mine Safety Disclosures](#ITEM4MINESAFETYDISCLOSURES_729119) | 29 |
| [Item 5.](#ITEM5OTHERINFORMATION_785228) | [Other Information](#ITEM5OTHERINFORMATION_785228) | 29 |
| [Item 6.](#ITEM6EXHIBITS_368004) | [Exhibits](#ITEM6EXHIBITS_368004) | 30 |
|  | [SIGNATURES](#SIGNATURES_969179) | 31 |

---

[**Table of Contents**](#TOC)

#### PART I - FINANCIAL INFORMATION

#### ITEM 1. FINANCIAL STATEMENTS
**ClearSign Technologies Corporation and Subsidiary**

**Condensed Consolidated Balance Sheets**

***(Unaudited)***

---

| | | |
|:---|:---|:---|
| (in thousands, except share and per share data) | **September 30,**  | **December 31,**  |
|  | **2025** | **2024** |
| **ASSETS** |  |  |
| Current Assets: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Cash and cash equivalents | $10488 | $14035 |
| &nbsp;&nbsp;&nbsp;&nbsp;Accounts receivable | 324 | 165 |
| &nbsp;&nbsp;&nbsp;&nbsp;Contract assets | 514 | 194 |
| &nbsp;&nbsp;&nbsp;&nbsp;Prepaid expenses and other assets | 420 | 454 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total current assets | 11746 | 14848 |
| Fixed assets, net | 223 | 238 |
| Patents and other intangible assets, net | 778 | 830 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total Assets | $12747 | $15916 |
| **LIABILITIES AND STOCKHOLDERS' EQUITY** |  |  |
| Current Liabilities: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Accounts payable and accrued liabilities | $1983 | $1220 |
| &nbsp;&nbsp;&nbsp;&nbsp;Current portion of lease liabilities | 94 | 75 |
| &nbsp;&nbsp;&nbsp;&nbsp;Accrued compensation and related taxes | 353 | 671 |
| &nbsp;&nbsp;&nbsp;&nbsp;Contract liabilities | 1148 | 73 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total current liabilities | 3578 | 2039 |
| Long Term Liabilities: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Long term lease liabilities | 91 | 113 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total liabilities | 3669 | 2152 |
| Commitments and contingencies (Note 9) |  |  |
| Stockholders' Equity: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Preferred stock, $0.0001 par value, 2,000,000 shares authorized, no shares issued or outstanding |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Common stock, $0.0001 par value, 87,500,000 shares authorized, 52,517,048 and 50,285,509 shares issued and outstanding at September 30, 2025 and December 31, 2024, respectively. | 5 | 5 |
| &nbsp;&nbsp;&nbsp;&nbsp;Additional paid-in capital | 113294 | 112796 |
| &nbsp;&nbsp;&nbsp;&nbsp;Accumulated other comprehensive loss | (20) | (21) |
| &nbsp;&nbsp;&nbsp;&nbsp;Accumulated deficit | (104201) | (99016) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total stockholders' equity | 9078 | 13764 |
|  | $12747 | $15916 |

---

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

[**Table of Contents**](#TOC)

**ClearSign Technologies Corporation and Subsidiary**

**Condensed Consolidated Statements of Operations and Comprehensive Loss**

***(Unaudited)***

---

| | | | | |
|:---|:---|:---|:---|:---|
| (in thousands, except share and per share data) | **For the Three Months Ended**  | **For the Three Months Ended**  | **For the Nine Months Ended**  | **For the Nine Months Ended**  |
|  | **September 30,**  | **September 30,**  | **September 30,**  | **September 30,**  |
|  | **2025** | **2024** | **2025** | **2024** |
| Revenues | $1029 | $1859 | $1563 | $3006 |
| Cost of goods sold | 661 | 1308 | 944 | 1976 |
| &nbsp;&nbsp;Gross profit | 368 | 551 | 619 | 1030 |
| Operating expenses: |  |  |  |  |
| &nbsp;&nbsp;Research and development | 310 | 329 | 1004 | 1012 |
| &nbsp;&nbsp;General and administrative | 1808 | 1655 | 5460 | 4840 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total operating expenses | 2118 | 1984 | 6464 | 5852 |
| Loss from operations | (1750) | (1433) | (5845) | (4822) |
| Other income, net: |  |  |  |  |
| &nbsp;&nbsp;Interest income | 105 | 146 | 353 | 284 |
| &nbsp;&nbsp;Government assistance | 216 | 131 | 307 | 395 |
| &nbsp;&nbsp;Other income, net |  | 1 |  | 8 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total other income, net | 321 | 278 | 660 | 687 |
| Net loss | $(1429) | $(1155) | $(5185) | $(4135) |
| Net loss per share - basic and fully diluted | $(0.03) | $(0.02) | $(0.09) | $(0.09) |
| Weighted average number of shares outstanding - basic and fully diluted | 55744062 | 54714910 | 55322077 | 46986914 |
| **Comprehensive loss:** |  |  |  |  |
| Net loss | $(1429) | $(1155) | $(5185) | $(4135) |
| &nbsp;&nbsp;Foreign-exchange translation adjustments | 1 | 5 | 1 | 1 |
| Comprehensive loss | $(1428) | $(1150) | $(5184) | $(4134) |

---

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

[**Table of Contents**](#TOC)

**ClearSign Technologies Corporation and Subsidiary**

**Condensed Consolidated Statements of Stockholders' Equity**

**For the Three Month Periods During the Nine Months Ended September 30, 2025 and 2024**

***(Unaudited)***

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  |  |  |  | **Accumulated Other** |  | **Total** |
| (in thousands, except per share data) | **Common Stock** | **Common Stock** | **Additional** | **Comprehensive** | **Accumulated** | **Stockholders'** |
|  | **Shares** | **Amount** | **Paid-In Capital** | **Loss** | **Deficit** | **Equity** |
| **Balances at December 31, 2024** | 50286 | $5 | $112796 | $(21) | $(99016) | $13764 |
| Share-based compensation, net of tax withholdings | 81 |  | 45 |  |  | 45 |
| Fair value of stock issued in payment of accrued compensation | 326 |  | 279 |  |  | 279 |
| Shares issued for services | 4 |  | 4 |  |  | 4 |
| Exercise of warrants | 23 |  | 24 |  |  | 24 |
| Exercise of prefunded warrants | 1703 |  |  |  |  |  |
| Net loss |  |  |  |  | (2076) | (2076) |
| **Balances at March 31, 2025** | 52423 | 5 | 113148 | (21) | (101092) | 12040 |
| Share-based compensation, net of tax withholdings |  |  | 51 |  |  | 51 |
| Shares issued for services | 3 |  | 3 |  |  | 3 |
| Net loss |  |  |  |  | (1680) | (1680) |
| **Balances at June 30, 2025** | 52426 | 5 | 113202 | (21) | (102772) | 10414 |
| Share-based compensation, net of tax withholdings |  |  | 38 |  |  | 38 |
| Shares issued for services | 91 |  | 54 |  |  | 54 |
| Foreign-exchange translation adjustment |  |  |  | 1 |  | 1 |
| Net loss |  |  |  |  | (1429) | (1429) |
| **Balances at September 30, 2025** | 52517 | $5 | $113294 | $(20) | $(104201) | $9078 |

---

[**Table of Contents**](#TOC)

**ClearSign Technologies Corporation and Subsidiary**

**Condensed Consolidated Statements of Stockholders' Equity**

**For the Three Month Periods During the Nine Months Ended September 30, 2025 and 2024**

***(Unaudited)***

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  |  |  |  | **Accumulated Other** |  | **Total** |
| (in thousands, except per share data) | **Common Stock** | **Common Stock** | **Additional** | **Comprehensive** | **Accumulated** | **Stockholders'** |
|  | **Shares** | **Amount** | **Paid-In Capital** | **Loss** | **Deficit** | **Equity** |
| **Balances at December 31, 2023** | 38687 | $4 | $98922 | $(17) | $(93717) | $5192 |
| Share-based compensation | 67 |  | 67 |  |  | 67 |
| Tax withholdings related to share-based compensation | (22) |  | (16) |  |  | (16) |
| Fair value of stock issued in payment of accrued compensation | 307 |  | 326 |  |  | 326 |
| Shares issued for services | 4 |  | 3 |  |  | 3 |
| Foreign-exchange translation adjustment |  |  |  | (3) |  | (3) |
| Net loss |  |  |  |  | (1108) | (1108) |
| **Balances at March 31, 2024** | 39043 | 4 | 99302 | (20) | (94825) | 4461 |
| Share-based compensation | 256 |  | 344 |  |  | 344 |
| Tax withholdings related to share-based compensation | (11) |  | (13) |  |  | (13) |
| Shares issued for services | 4 |  | 3 |  |  | 3 |
| Issuance of common stock in public offering, net of expenses | 5314 | 1 | 2390 |  |  | 2391 |
| Issuance of warrants in public offering, net of expenses |  |  | 1831 |  |  | 1831 |
| Issuance of common stock in private placement, net of expenses | 2250 |  | 865 |  |  | 865 |
| Issuance of prefunded warrants in private placement, net of expenses |  |  | 1214 |  |  | 1214 |
| Issuance of warrants in private placement, net of expenses |  |  | 2389 |  |  | 2389 |
| Issuance of common stock for participation right exercise, net of expenses | 3350 |  | 1447 |  |  | 1447 |
| Issuance of prefunded warrants for participation right exercise, net of expenses |  |  | 580 |  |  | 580 |
| Issuance of warrants for participation right exercise, net of expenses |  |  | 2250 |  |  | 2250 |
| Foreign-exchange translation adjustment |  |  |  | (1) |  | (1) |
| Net loss |  |  |  |  | (1872) | (1872) |
| **Balances at June 30, 2024** | 50206 | 5 | 112602 | (21) | (96697) | 15889 |
| Share-based compensation |  |  | 73 |  |  | 73 |
| Tax withholdings related to share-based compensation |  |  | (9) |  |  | (9) |
| Shares issued for services | 29 |  | 20 |  |  | 20 |
| Foreign-exchange translation adjustment |  |  |  | 5 |  | 5 |
| Net loss |  |  |  |  | (1155) | (1155) |
| **Balances at September 30, 2024** | 50235 | $5 | $112686 | $(16) | $(97852) | $14823 |

---

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

[**Table of Contents**](#TOC)

**ClearSign Technologies Corporation and Subsidiary**

**Condensed Consolidated Statements of Cash Flows**

***(Unaudited)***

---

| | | |
|:---|:---|:---|
| (in thousands) | **For the Nine Months Ended September 30,**  | **For the Nine Months Ended September 30,**  |
|  | **2025** | **2024** |
| **Cash flows from operating activities:** |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Net loss | $(5185) | $(4135) |
| &nbsp;&nbsp;&nbsp;&nbsp;Adjustments to reconcile net loss to net cash used in operating activities: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Common stock issued for services | 61 | 26 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Share-based compensation, net of tax withholdings | 863 | 446 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Depreciation and amortization | 145 | 138 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Impairment of intangible assets |  | 17 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Right-of-use asset amortization | 66 | 64 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Lease amendments |  | (3) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Change in operating assets and liabilities: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Contract assets | (320) | 39 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Accounts receivable | (159) | (462) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Prepaid expenses and other assets | 34 | (260) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Accounts payable, accrued liabilities, and lease liabilities | 6 | 1091 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Accrued compensation and related taxes | (39) | 23 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Contract liabilities | 1075 | (942) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Net cash used in operating activities | (3453) | (3958) |
| **Cash flows from investing activities:** |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Acquisition of fixed assets | (4) | (18) |
| &nbsp;&nbsp;&nbsp;&nbsp;Disbursements for patents and other intangible assets | (74) | (159) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Net cash used in investing activities | (78) | (177) |
| **Cash flows from financing activities:** |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Proceeds from issuance of common stock, net of offering costs |  | 12967 |
| &nbsp;&nbsp;&nbsp;&nbsp;Proceeds from exercise of warrants | 24 |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Taxes paid related to vesting of restricted stock units | (41) | (31) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Net cash provided by (used in) financing activities | (17) | 12936 |
| **Effect of exchange rate changes on cash and cash equivalents** | 1 | 1 |
| **Net change in cash and cash equivalents** | (3547) | 8802 |
| **Cash and cash equivalents, beginning of period** | 14035 | 5684 |
| **Cash and cash equivalents, end of period** | $10488 | $14486 |
| **Supplemental disclosure of cash flow information:** |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Officer and employee equity awards for prior year accrued compensation | $279 | $326 |
| &nbsp;&nbsp;&nbsp;&nbsp;Non-cash impact of new lease | $68 | $32 |

---

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

[**Table of Contents**](#TOC)

**ClearSign Technologies Corporation**

**Notes to Unaudited Condensed Consolidated Financial Statements**

#### Note 1 – Organization and Description of Business
ClearSign Technologies Corporation ("ClearSign" or the "Company") designs and develops products and technologies for the purpose of decarbonization and improving key performance characteristics of industrial and commercial systems, including operational performance, energy efficiency, emission reduction, safety, and overall cost-effectiveness. The Company's patented technologies are designed to be embedded in established original equipment manufacturers ("OEM") products as ClearSign Core™ and ClearSign Eye and other sensing configurations in order to enhance the performance of combustion systems and fuel safety systems in a broad range of markets. These markets include energy (upstream oil production and down-stream refining), commercial/industrial boiler, chemical, petrochemical, transport and power industries. The Company's primary technology is its ClearSign Core™ technology, which achieves very low emissions without the need of selective catalytic reduction.

The Company was originally incorporated in the State of Washington in 2008. During January 2022, the Company relocated its headquarters from Seattle, Washington to Tulsa, Oklahoma. Effective June 15, 2023, the Company changed its state of incorporation to Delaware. On July 28, 2017, the Company incorporated a subsidiary, ClearSign Asia Limited, in Hong Kong to represent the Company's business and technological interests throughout Asia. Through ClearSign Asia Limited, the Company has established a wholly foreign owned enterprise in China – ClearSign Combustion (Beijing) Environmental Technologies Co., LTD. On August 22, 2024, the Company's Board of Directors (the "Board") authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company's Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years. The Company can revive its China operations at any time during those three years with minimal cost impact. The effective date of our dormancy filing was March 12, 2025.

Unless otherwise stated or the context otherwise requires, the terms "we," "us," "our," "ClearSign" and the "Company" refer to ClearSign Technologies Corporation and its subsidiary, ClearSign Asia Limited.

#### Business Segments
The Company operates in one operating and reportable segment engaged in the design, development and sale of combustion technologies that improve the performance and cost-effectiveness of industrial combustion systems, referred to herein as the "Combustion" segment. The Company manages its business activities on a consolidated basis. Since the operations comprise a single reportable segment, amounts reported in the consolidated balance sheets, statements of operations and comprehensive loss, stockholders' equity, and cash flows represent the activities of the Combustion segment.

The Combustion segment derives revenues by delivering products and technology solutions to OEM's and end-users. Our products and solutions can be incorporated into a new or existing customer infrastructure or equipment. Customer contracts can include multiple billing milestones and performance obligations. The Company can typically satisfy its performance obligations within a twelve month period, but customer project delays, some of which can be beyond the Company's control, can impact timing of performance and there is no assurance we will satisfy all performance obligations in such period of time.

The Company's Chief Executive Officer, who is the chief operating decision maker ("CODM"), reviews quarterly financial information on a consolidated basis for making operating decisions, allocating resources and evaluating financial performance. The CODM consistently reviews the consolidated statements of operations and comprehensive loss to manage operations and monitor performance against management expectations. Factors considered by the CODM when assessing a reportable segment include factors such as, but not limited to, human capital, intellectual property, customer relationships and business model design.

[**Table of Contents**](#TOC)

Substantially all the Company's operating activities, including its long-lived assets, are located within the United States. Customers in the United States accounted for 100% of revenues during the three and nine months ended September 30, 2025 and 2024. The Company disaggregates geographical revenues by selling location, since many of our target customers are global entities, and it would be more likely than not, that these customers would negotiate sales within our current territory in the United States.

#### Note 2 – Summary of Significant Accounting Policies
Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the "SEC") for reporting on Form 10-Q. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles have been condensed or omitted pursuant to such rules and regulations. The condensed consolidated balance sheet at December 31, 2024 has been derived from the Company's audited consolidated financial statements as of that date.

In the opinion of management, these condensed consolidated financial statements reflect all normal recurring and other adjustments necessary for a fair presentation. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2024. Operating results for interim periods are not necessarily indicative of operating results for an entire fiscal year or any other future periods.

The accompanying unaudited condensed consolidated financial statements include the accounts of ClearSign and its subsidiary. Intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Research and Development

The cost of research and development is expensed as incurred. Research and development costs consist of salaries, benefits, share-based compensation, consumables, and consulting fees, including costs to develop and test prototype equipment and parts. Research and development costs have been offset by funds received, if any, from strategic partners in cost sharing and/or collaborative projects. During the three and nine months ended September 30, 2025, the Company received no funds from these types of arrangements. During the three and nine months ended September 30, 2024, the Company received $28 thousand and $135 thousand, respectively, from these types of arrangements.

Foreign Operations

The accompanying unaudited condensed consolidated balance sheets as of September 30, 2025 and December 31, 2024 include assets amounting to approximately $145 thousand and $145 thousand, respectively, relating to the operations of ClearSign Asia Limited. The Beijing registered capital requirement is $350 thousand, which is required to be paid by June 30, 2032, $211 thousand of which has been paid as of September 30, 2025. On August 22, 2024, the Board authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company's Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years. The Company can revive its China operations at any time during those three years with minimal cost impact. The dormancy filing became effective as of March 12, 2025.

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Recently Issued Accounting Pronouncements

In December 2023, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2023-09, *Income Taxes (Topic 740): Improvements to Income Tax Disclosures* ("ASU 2023-09") to enhance the transparency and decision-making usefulness of income tax disclosures by requiring additional information on an entity's tax rate reconciliation, as well as income taxes paid. ASU 2023-09 is effective for our reporting period beginning January 1, 2025. We are currently assessing the impact that the adoption of ASU 2023-09 will have on the disclosures in our annual consolidated financial statements.

In November 2024, FASB issued ASU No. 2024-03, *Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures* (Subtopic 220-40) ("ASU 2024-03"). ASU 2024-03 requires enhanced disclosures about types of expenses, including purchases of inventory, employee compensation, depreciation, and amortization, in commonly presented expense captions. The amendments are effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. Entities may apply the amendments prospectively or retrospectively to any or all prior periods presented in the financial statements. We are currently evaluating the impact that this guidance will have on the disclosures within our consolidated financial statements. While ASU 2024-03 will impact only our disclosures and not our financial condition and results of operations, we are assessing when we will adopt the ASU 2024-03.

In May 2025, FASB issued ASU No. 2025-04, *Compensation—Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606): Clarifications to Share-Based Consideration Payable to a Customer* ("ASU 2025-04"), which clarifies the guidance on the accounting for share-based payment awards that are granted by an entity as consideration payable to its customer, with the intent to reduce diversity in practice and improve existing guidance by revising the definition of a "performance condition" and eliminating a forfeiture policy election for service conditions associated with share-based consideration payable to a customer. ASU 2025-04 also clarifies the guidance in Topic 606 on the variable consideration constraint does not apply to share-based consideration payable to a customer "regardless of whether an award's grant date has occurred." ASU 2025-04 is effective for our reporting period beginning January 1, 2027, with early adoption permitted. We are currently assessing the impact that the adoption of ASU 2025-04 will have on the disclosures in our annual consolidated financial statements.

In July 2025, the FASB issued ASU 2025-05, *Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets* ("ASU 2025-05"), which amends ASC 326-20 to provide a practical expedient (for all entities) and an accounting policy election (for all entities, other than public business entities, that elect the practical expedient) related to the estimation of expected credit losses for current accounts receivable and current contract assets that arise from transactions accounted for under Revenue from Contracts with Customers ("ASC 606"). The standard is effective for annual reporting periods beginning after December 15, 2025, including interim periods, and allows for early adoption. The Company is currently evaluating the impacts of the adoption of ASU 2025-05 on the consolidated financial statements and related disclosures.

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#### Note 3 – Fixed Assets, Net
Fixed Assets, Net

Fixed assets, net are summarized as follows:

---

| | | |
|:---|:---|:---|
|  | September 30,  | December 31,  |
| &nbsp;&nbsp;*(in thousands)* | 2025 | 2024 |
| Office furniture and equipment | $103 | $99 |
| Leasehold improvements | 43 | 43 |
|  | 146 | 142 |
| Accumulated depreciation and amortization | (103) | (85) |
|  | 43 | 57 |
| Operating lease ROU assets, net | 180 | 181 |
| Total | $223 | $238 |

---

Depreciation expense for the three and nine months ended September 30, 2025 was $7 thousand and $19 thousand, respectively.

Depreciation expense for the three and nine months ended September 30, 2024 was $4 thousand and $15 thousand, respectively.

Leases

The Company leases office space in Tulsa, Oklahoma, Seattle, Washington, and Beijing, China. During May 2025, the Company renewed its Beijing, China lease for 24 months with monthly rent at approximately $3 thousand. As a result of this renewal, the Company increased the right-of-use ("ROU") asset and lease liability by $68 thousand during the nine months ended September 30, 2025.

During October 2024, the Company entered into a sub-lease agreement to rent office space in Seattle for approximately $2 thousand per month for twelve months. The Seattle lease is considered a short-term lease, as the lease term is 12 months or less from the commencement date. The Seattle lease was renewed in October 2025 with similar terms. The short-term lease expense for the three and nine months ended September 30, 2025 was approximately $6 thousand and $17 thousand, respectively. The short-term lease expense for the three and nine months ended September 30, 2024 was approximately $5 thousand and $16 thousand, respectively. The Tulsa and Beijing leases are classified as operating leases, each with remaining terms of approximately two years; contractual language requires renewal negotiations to occur at or near termination. These leases are normal and customary for office space, in that, contractual guarantees exist requiring the lessee return the premises to its original functional state.

The Tulsa lease contains fixed annual lease payments that increase annually by 2%. The Seattle, Tulsa, and Beijing total monthly minimum rent is approximately $10 thousand, in the aggregate. Operating lease costs for the three and nine months ended September 30, 2025 were $24 thousand and $73 thousand, respectively. Operating lease costs for the three and nine months ended September 30, 2024 were $25 thousand and $73 thousand, respectively.

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Supplemental balance sheet information related to operating leases is as follows:

---

| | | |
|:---|:---|:---|
|  | September 30,  | December 31,  |
| &nbsp;&nbsp;*(in thousands)* | 2025 | 2024 |
| Operating lease ROU assets, net | $180 | $181 |
| Lease Liabilities: |  |  |
| &nbsp;&nbsp;Current lease liabilities | $94 | $75 |
| &nbsp;&nbsp;Long term lease liabilities | 91 | 113 |
| Total lease liabilities | $185 | $188 |
| Weighted average remaining lease term (in years): | 1.9 | 2.6 |
| Weighted average discount rate: | 4.4% | 5.3% |

---

Supplemental cash flow information related to operating leases is as follows:

---

| | | |
|:---|:---|:---|
|  | For the Nine Months Ended  | For the Nine Months Ended  |
|  | September 30,  | September 30,  |
| &nbsp;&nbsp;*(in thousands)* | 2025 | 2024 |
| Cash paid for amounts included in the measurement of lease liabilities: |  |  |
| &nbsp;&nbsp;Operating cash flows used in operating leases | $74 | $73 |
| Non-cash impact of new leases and lease modifications |  |  |
| &nbsp;&nbsp;Change in operating lease liabilities | $68 | $29 |
| &nbsp;&nbsp;Change in operating lease ROU assets | $68 | $32 |

---

Minimum future payments under the Company's operating lease liabilities as of September 30, 2025 are as follows:

---

| | |
|:---|:---|
| &nbsp;&nbsp;*(in thousands)* |  |
| 2025 (remaining) | $25 |
| 2026 | 101 |
| 2027 | 68 |
| &nbsp;&nbsp;Total future lease payments | 194 |
| Less: imputed interest | (9) |
|  | $185 |

---

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#### Note 4 – Patents and Other Intangible Assets
Patents and other intangible assets are summarized as follows:

---

| | | |
|:---|:---|:---|
|  | September 30,  | December 31,  |
| &nbsp;&nbsp;*(in thousands)* | 2025 | 2024 |
| Patents |  |  |
| &nbsp;&nbsp;Patents pending | $378 | $346 |
| &nbsp;&nbsp;Issued patents | 1076 | 1034 |
|  | 1454 | 1380 |
| Trademarks |  |  |
| &nbsp;&nbsp;Registered trademarks | 86 | 86 |
|  | 86 | 86 |
| Other | 8 | 8 |
|  | 1548 | 1474 |
| Accumulated amortization | (770) | (644) |
|  | $778 | $830 |

---

Amortization expense for three and nine months ended September 30, 2025 was $41 thousand and $126 thousand, respectively.

Amortization expense for three and nine months ended September 30, 2024 was $43 thousand and $123 thousand, respectively.

Future amortization expense associated with issued patents and registered trademarks as of September 30, 2025 is as follows:

---

| | |
|:---|:---|
| &nbsp;&nbsp;*(in thousands)* |  |
| 2025 (remaining) | $36 |
| 2026 | 134 |
| 2027 | 110 |
| 2028 | 74 |
| 2029 | 34 |
| Thereafter | 4 |
|  | $392 |

---

The amortization life for patents ranges between three to five years and trademark lives are set at ten years. The Company does not amortize patents or trademarks classified as pending.

During the three and nine months ended September 30, 2025 and 2024, the Company assessed its patent and trademark assets. The Company also evaluated its strategic approach to the pursuit and protection of its intellectual property. It is the intent of the Company to continue to pursue intellectual property protection. If the Company identifies certain assets where the intellectual property does not directly align with its core technology, the Company will impair the intangible asset and write-off the asset as an expense.

#### Note 5 – Revenue, Contract Assets and Contract Liabilities
The Company's contracts with customers generally have performance obligations and a schedule of non-refundable cancellation obligations. Performance obligations typically fall into one of three categories, product shipment, burner performance tests and engineering design. Customer payment milestones are unique to individual contracts and may occur prior to completion of performance obligations. Customer payment terms typically range between thirty and sixty

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days from the date of billing. Our customer contracts typically have a duration of less than twelve months. Delays in contract performance, if any, typically occur as a result of customer onsite project delays outside of our control.

The Company recognized $1,029 thousand of revenues and $661 thousand of cost of goods sold during the three months ended September 30, 2025. The revenue and cost of goods sold were related to delivering spare parts to multiple customers, delivering a flare order, delivering a mid-stream order, completing a customer witness test, finalizing a Computational Fluid Dynamic ("CFD") analysis, and providing engineering services. These products and services constitute performance obligations.

The Company recognized $1,563 thousand of revenues and $944 thousand of cost of goods sold during the nine months ended September 30, 2025. The revenue and cost of goods sold relate to spare parts orders for multiple customers, a performance burner test, flare order, engineering services, sales of boiler burners, and the successful completion of CFD analysis. These products and services constitute performance obligations.

The Company recognized $1,859 thousand of revenues and $1,308 thousand of cost of goods sold during the three months ended September 30, 2024. The revenue and cost of goods sold predominantly relate to the delivery of multiple process burners to a single customer. The delivery of products constitutes performance obligations.

The Company recognized $3,006 thousand of revenues and $1,976 thousand of cost of goods sold during the nine months ended September 30, 2024. The revenue and cost of goods sold predominantly relate to the Company's process burner product line. The Company delivered multiple burners for different customers, successfully completed engineering feasibility studies, including CFD analysis, and fulfilled multiple spare parts orders. These products and services constitute performance obligations.

The Company had contract assets of $514 thousand and $194 thousand at September 30, 2025 and December 31, 2024, respectively. The Company had contract liabilities of $1,148 thousand and $73 thousand at September 30, 2025 and December 31, 2024, respectively. Of the $73 thousand contract liabilities balance at December 31, 2024, the Company recognized revenue of $39 thousand and $73 thousand during the three and nine months ended September 30, 2025, respectively.

**Note 6 – Product Warranties**

A summary of the Company's warranty liability activity, which is included in accounts payable and accrued liabilities in the accompanying condensed consolidated balance sheets as of September 30, 2025 and December 31, 2024, is as follows:

---

| | | |
|:---|:---|:---|
|  | September 30,  | December 31,  |
| &nbsp;&nbsp;*(in thousands)* | 2025 | 2024 |
| Warranty liability at beginning of year | $471 | $110 |
| Accruals | 100 | 478 |
| Payments | (176) | (114) |
| Changes related to expirations and settlements | (31) | (3) |
| Warranty liability at end of period | $364 | $471 |

---

#### Note 7 – Equity
Common Stock and Preferred Stock

The Company is authorized to issue 87.5 million shares of common stock and 2.0 million shares of preferred stock. Preferences, limitations, voting powers and relative rights of any preferred stock to be issued may be determined by the Board. The Company has not issued any shares of preferred stock.

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The Company has an At-The-Market ("ATM") program pursuant to an ATM Offering Agreement with H.C. Wainwright & Co., LLC ("Wainwright") as sales agent, dated July 17, 2025 (the "Sales Agreement"), pursuant to which the Company may sell shares of common stock with an aggregate offering price of up to $10.39 million. As of the date of this report, no shares have been sold pursuant to the Sales Agreement. We previously had an ATM program with Virtu Americas LLC (the "Virtu ATM"), which was terminated effective as of July 12, 2025.

The Company is currently subject to the SEC's "baby shelf rules," which prohibit companies with a public float of less than $75 million from issuing securities under a "shelf" registration statement in excess of one-third of such company's public float in a 12-month period. These rules may limit future issuances of shares by the Company under our "shelf" registration statement on Form S-3, including through the ATM program with Wainwright or other securities offerings.

Warrants and Pre-Funded Warrants

The following table summarizes the activity and outstanding balance of our outstanding warrants and pre-funded warrants as of September 30, 2025, along with the associated weighted average exercise price and weighted average remaining life for such warrants and pre-funded warrants.

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Warrants**  | **Warrants**  | **Warrants**  | **Warrants**  | **Pre-Funded Warrants**<sup>(1)</sup>  | **Pre-Funded Warrants**<sup>(1)</sup>  | **Pre-Funded Warrants**<sup>(1)</sup>  |
| &nbsp;&nbsp;(*in thousands, except per share data*) | Number | Wtd. Avg. Exercise Price  | Wtd. Avg. Remaining Life (in years)  | Aggregate Intrinsic Value | Number | Wtd. Avg. Exercise Price | Aggregate Intrinsic Value |
| Outstanding at Beginning of Year | 21295 | $1.0535 | 4.74 | $8230 | 4499 | $0.0001 | $6478 |
| Granted |  |  |  |  |  |  |  |
| Exercised  | (23) | 1.0500 |  |  | (1703) | 0.0001 |  |
| Forfeited/Expired  |  |  |  |  |  |  |  |
| Outstanding at Period End  | 21272 | $1.0535 | 3.99 | $— | 2796 | $0.0001 | $2156 |
| *(1) Pre-funded warrants have no expiration date and only expire when exercised in full.*  | *(1) Pre-funded warrants have no expiration date and only expire when exercised in full.*  | *(1) Pre-funded warrants have no expiration date and only expire when exercised in full.*  | *(1) Pre-funded warrants have no expiration date and only expire when exercised in full.*  | *(1) Pre-funded warrants have no expiration date and only expire when exercised in full.*  | *(1) Pre-funded warrants have no expiration date and only expire when exercised in full.*  | *(1) Pre-funded warrants have no expiration date and only expire when exercised in full.*  |  |

---

Refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2024 for additional details related to our outstanding warrants and pre-funded warrants.

Equity Incentive Plan

On June 17, 2021, the Company's stockholders approved and the Company adopted the ClearSign Technologies Corporation 2021 Equity Incentive Plan (the "2021 Plan") which permits the Company to grant incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units, performance units, and performance shares, to eligible participants, which includes employees, directors and consultants. The Board's Human Capital and Compensation Committee (the "Compensation Committee") is authorized to administer the 2021 Plan.

The 2021 Plan provides for an annual increase in available shares equal to the lesser of (i) 10% of the aggregate number of shares of common stock issued by the Company in the prior fiscal year; or (ii) such number provided by the Compensation Committee; provided, however, that the total cumulative increase in the number of shares available for issuance pursuant to this automatic share increase shall not exceed 400 thousand shares of common stock. In 2025, the Board did not exercise its right to limit the automatic increase. Accordingly, the 2021 Plan share reserve increased by 400 thousand shares.

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Ending balances for the 2021 Plan is as follows:

---

| | | |
|:---|:---|:---|
|  | September 30,  | December 31,  |
| &nbsp;&nbsp;(*in thousands*) | 2025 | 2024 |
| Outstanding options and restricted stock units | 2874 | 3316 |
| Reserved but unissued shares under the Plan | 2292 | 1858 |
| Reserved but unissued shares at end of period | 5166 | 5174 |

---

Stock Options

Under the terms of the 2021 Plan, incentive stock options and nonstatutory stock options must have an exercise price at or above the fair market value on the date of the grant. At the time of grant, the Company will determine the period within which the option may be exercised and will specify any conditions that must be satisfied before the option vests and may be exercised. The Company estimates the fair value of stock options on the date of grant using the Black-Scholes option pricing model.

As permitted by SEC Staff Accounting Bulletin 107, management utilized the simplified approach to estimate the expected term of the options, which represents the period of time that options granted are expected to be outstanding. Expected volatility has been determined through the Company's historical stock price volatility. The Company has not made an estimate of forfeitures at the time of the grant, but rather accounts for forfeitures at the time they occur. The risk-free rate for periods within the expected life of the option is based on the U.S. Treasury yield in effect at the time of grant. The Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

*Equity Incentive Plan Options*

Compensation expense associated with stock option awards for the three and nine months ended September 30, 2025 totaled $4 thousand and $42 thousand, respectively. Compensation expense associated with stock option awards for the three and nine months ended September 30, 2024 totaled $37 thousand and $87 thousand, respectively.

A summary of the Company's 2011 Equity Incentive Plan and the 2021 Plan stock option activity and changes are as follows:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | September 30,  | September 30,  | September 30,  | September 30,  |
|  | 2025 | 2025 | 2025 | 2025 |
| &nbsp;&nbsp;(*in thousands, except per share data*) | Options to Purchase Common Stock | Weighted Average Exercise Price | Weighted Average Remaining Contractual Life (in years) | Aggregate Intrinsic Value |
| Outstanding at beginning of year | 2452 | $2.04 | 4.92 | $496 |
| Granted |  | $— |  |  |
| Exercised |  | $— |  |  |
| Forfeited/Expired | (55) | $2.56 |  |  |
| Outstanding at end of period | 2397 | $2.03 | 3.89 | $13 |
| Exercisable at end of period | 1872 | $1.70 | 3.49 | $13 |

---

The intrinsic value is the difference between the Company's common stock price and the option exercise prices multiplied by the number of in-the-money options. This amount changes based on the fair value of the Company's common stock.

At September 30, 2025, there was $244 thousand of total unrecognized compensation cost related to non-vested stock option-based compensation arrangements. Vesting criteria ranges from time-based to performance-based. The Company records costs for time-based arrangements ratably across the timeframe, whereas performance-based arrangements require management to continually evaluate predetermined goals against actual circumstances. The maximum contractual term for these options are ten years from the grant date.

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*Inducement Options*

During the year ended December 31, 2023, the Company granted non-qualified stock options to its Chief Technology Officer to purchase an aggregate of 150 thousand shares of common stock with an exercise price of $0.91 per share as a material inducement to accept employment with the Company. These inducement options vest in three equal installments, with one third of the option vesting on the grant date, and each remaining third vesting on the second and third anniversaries of the grant date, subject to continued employment with the Company. The fair value of these inducement options was $112 thousand, which was estimated on the grant date using the Black-Scholes valuation model. The compensation expense recognized for these inducement options for the three and nine months ended September 30, 2025 was $10 thousand and $28 thousand, respectively. The compensation expense recognized for these inducement options for the three and nine months ended September 30, 2024 was $9 thousand and $28 thousand, respectively. Total unrecognized compensation expense for these inducement options as of September 30, 2025 was $4 thousand.

These inducement options were granted outside of the 2021 Plan and in accordance with the employment inducement exemption provided under Nasdaq Listing Rule 5635(c)(4).

A summary of the Company's inducement option activity and changes are as follows:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | September 30,  | September 30,  | September 30,  | September 30,  |
|  | 2025 | 2025 | 2025 | 2025 |
| &nbsp;&nbsp;(*in thousands, except per share data*) | Options to Purchase Common Stock | Weighted Average Exercise Price | Weighted Average Remaining Contractual Life (in years) | Aggregate Intrinsic Value |
| Outstanding at beginning of year | 491 | $1.53 | 3.04 | $119 |
| Granted |  | $— |  |  |
| Exercised |  | $— |  |  |
| Forfeited/Expired |  | $— |  |  |
| Outstanding at end of period | 491 | $1.53 | 2.29 | $— |
| Exercisable at end of period | 441 | $1.60 | 2.54 | $— |

---

Restricted Stock Units

The Company awards its directors and certain employees restricted stock units ("RSUs") in lieu of cash payment for compensation. These awards are granted pursuant to the 2021 Plan. Employee vesting criteria is time based, and compensation expense is recognized ratably across the timeframe. The Company pays payroll withholding taxes on behalf of the employee at vesting by withholding shares from the employee's award to cover the taxes payable in connection with such vesting. The Company accrued taxes for RSU share-based compensation of $38 thousand and $38 thousand for the nine months ended September 30, 2025 and 2024, respectively. Total unrecognized compensation expense for employee RSUs as of September 30, 2025 was $214 thousand.

Director vesting criteria is contingent upon the occurrence of one of four future events, which the Company cannot predict or control. Therefore, compensation expense for director RSUs is not recognized until one of these four future events occur in accordance with FASB ASC Topic 718*, Compensation – Stock Compensation*. Total unrecognized compensation expense for director services as of September 30, 2025 was $98 thousand. Director compensation is earned on a quarterly basis with the target value of compensation set at approximately $75 thousand per quarter, assuming five directors, one chairperson for each committee and two committee members for each of the three committees. As of September 30, 2025, we had four directors. On May 27, 2025, David M. Maley notified the Company that he would not stand for re-election as a director of the Company upon the expiration of his current term, which expired at the Company's 2025 annual meeting of stockholders held on July 25, 2025. In addition, Judith S. Schrecker and Catharine M. de Lacy both resigned from the Board and its committees effective as of August 4, 2025.

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A summary of the Company's RSUs activity is as follows:

---

| | | | |
|:---|:---|:---|:---|
|  | September 30,  | September 30,  | September 30,  |
|  | 2025 | 2025 | 2025 |
| &nbsp;&nbsp;(*in thousands, except per share data*) | Number of Shares | Weighted Average Grant Date Fair Value | Weighted Average Contractual Life (in years) <sup>(1)</sup> |
| Nonvested at beginning of year | 865 | $0.99 | 0.88 |
| Granted | 549 | $0.80 |  |
| Vested | (877) | $0.96 |  |
| Forfeited | (60) | $0.92 |  |
| Nonvested at end of period | 477 | $0.84 | 1.11 |

---

*1)* *The weighted average contractual life calculation excludes the number of director RSUs that vest upon one of four performance events (refer to discussion above for details).*

A summary of the Company's RSU compensation expense is as follows:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | For the Three Months Ended  | For the Three Months Ended  | For the Nine Months Ended  | For the Nine Months Ended  |
|  | September 30,  | September 30,  | September 30,  | September 30,  |
| &nbsp;&nbsp;(*in thousands, except per share data*) | 2025 | 2024 | 2025 | 2024 |
| Share-based compensation expense | $765 | $27 | $831 | $369 |
| Weighted average value per share | $0.93 | $0.93 | $0.93 | $1.29 |

---

During the three months ended September 30, 2025, 756 thousand RSUs vested but remained unissued as of September 30, 2025, which impacted share-based compensation expense and accrued liabilities by $729 thousand. The 756 thousand RSUs vested as a result of two directors resigning from the Board and another director that chose to not stand for re-election at the Company's 2025 annual meeting of stockholders.

Stock Awards

The Company awards employees stock in lieu of cash payment for compensation, typically to satisfy accrued bonus compensation. The awards are granted from the 2021 Plan.

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  | 2025 | 2025 | 2025 | 2024 | 2024 | 2024 |
| &nbsp;&nbsp;(*in thousands, except per share data*) | Number of Shares | Fair Value | Weighted Average per Share | Number of Shares | Fair Value | Weighted Average per Share |
| Fair value of stock payments in accrued compensation | 326 | $279 | $0.85 | 307 | $326 | $1.06 |

---

Consultant Stock Plan

The Company's 2013 Consultant Stock Plan (the "Consultant Plan") provides for the granting of shares of common stock to consultants who provide services related to capital raising, investor relations, and making a market in or promoting the Company's securities. The Company's officers, employees, and Board members are not entitled to receive grants from the Consultant Plan. The Compensation Committee is authorized to administer the Consultant Plan and establish the grant terms. The Consultant Plan provides for quarterly increases in the available number of authorized shares equal to the lesser of 1% of any new shares issued by the Company during the quarter immediately prior to the adjustment date or such lesser amount as the Board shall determine.

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The Consultant Plan activity is as follows:

---

| | |
|:---|:---|
|  | September 30,  |
| &nbsp;&nbsp;(*in thousands*) | 2025 |
| Reserved but unissued shares at beginning of period | 264 |
| Increases in the number of authorized shares | 30 |
| Grants | (98) |
| Reserved but unissued shares at end of period | 196 |

---

The Consultant Plan compensation expense is summarized as follows:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | For the Three Months Ended  | For the Three Months Ended  | For the Nine Months Ended  | For the Nine Months Ended  |
|  | September 30,  | September 30,  | September 30,  | September 30,  |
| &nbsp;&nbsp;(*in thousands, except per share data*) | 2025 | 2024 | 2025 | 2024 |
| Share-based compensation expense | $54 | $20 | $61 | $26 |
| Weighted average value per share | $0.59 | $0.72 | $0.62 | $0.74 |

---

#### Note 8 – Net Loss per Common Share
The Company calculates net loss per common stock in accordance with ASC Topic 260, "Earnings Per Share" ("ASC 260"). Basic and diluted net loss per common stock was determined by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Under ASC 260, shares issuable for little or no cash consideration are considered outstanding common stock and included in the computation of basic net loss per share. As such, for the three and nine months ended September 30, 2025 and 2024, the Company included its outstanding pre-funded warrants in its computation of net loss per share. The pre-funded warrants were issued in April and June 2024 and are each exercisable into one share of common stock at an exercise price of $0.0001 per share. In addition, 756 thousand shares were included in the weighted average number of shares outstanding for RSUs that vested but were unissued as of September 30, 2025.

The following potentially dilutive securities have not been included in the computation of diluted net loss per share for the three and nine months ended September 30, 2025 and 2024, as the result would be anti-dilutive:

---

| | | |
|:---|:---|:---|
|  | September 30,  | September 30,  |
| &nbsp;&nbsp;(*in thousands*) | 2025 | 2024 |
| Stock Options | 2888 | 3148 |
| Restricted Stock Units | 477 | 768 |
| Warrants | 21272 | 21319 |
| Total shares excluded from calculation | 24637 | 25235 |

---

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#### N ote 9 – Commitments and Contingencies
Litigation

From time to time the Company may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. Litigation is subject to inherent uncertainties and an adverse result in any such matter may harm the Company's business. As of the date of this report, the Company is not a party to any material pending legal proceedings or claims that the Company believes will have a material adverse effect on the business, financial condition or operating results.

Indemnification Agreements

The Company maintains indemnification agreements with our directors and officers that may require the Company to indemnify these individuals against liabilities that arise by reason of their status or service as directors or officers, except as prohibited by law.

**Note 10 – Government Assistance**

During 2022, the Company was awarded a research grant from the Department of Energy ("DOE") for approximately $250 thousand with the completion of such grant occurring in March 2023. The purpose of the grant was to produce a research paper for a flexible fuel ultra-low NOx process burner capable of burning 100% hydrogen fuel. During 2023, the Company was awarded a Phase 2 grant from the DOE to continue developing this ultra-low NOx hydrogen burner. The Phase 2 grant amount totaled approximately $1.6 million over a two-year period. These awards allow the Company to request reimbursements for expenditures such as labor, material, and administrative costs. During the three and nine months ended September 30, 2025, the Company recognized $216 thousand and $307 thousand in reimbursements from the DOE, respectively. During the three and nine months ended September 30, 2024, the Company recognized $116 thousand and $332 thousand in reimbursements from the DOE, respectively.

Beginning in 2021, the Company received funds relating to the Oklahoma 21<sup>st</sup> Century Quality Jobs Act. The estimated duration of the program is up to 10 years and is designed to attract growth industries to Oklahoma. By reporting quarterly salary statistics and meeting agreed upon employment thresholds, the state remits benefit monies to the Company. During three and nine months ended September 30, 2025, the Company did not receive any funds from this program. During three and nine months ended September 30, 2024, the Company recognized $17 thousand and $64 thousand in government assistance from this program, respectively.

**Note 11 – Subsequent Events**

On October 27, 2025, 756 thousand shares of common stock were issued to three former directors to satisfy our outstanding RSU liability recorded as of September 30, 2025 (see "Note 7 – Equity Restricted Stock Units" above for additional information).

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**SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS AND OTHER INFORMATION CONTAINED IN THIS REPORT**

This Quarterly Report on Form 10-Q (this "Form 10-Q" or "report") contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and the provisions of Section 27A of the Securities Act of 1933, as amended (the "Securities Act"), and Section 21E of the Securities Exchange Act of 1934, as amended (the "Exchange Act"). Forward-looking statements give our current expectations or forecasts of future events. You can identify these statements by the fact that they do not relate strictly to historical or current facts. You can find many (but not all) of these statements by looking for words such as "approximates," "believes," "hopes," "expects," "anticipates," "estimates," "projects," "intends," "plans," "would," "should," "could," "may," "will" or other similar expressions in this report. In particular, these include statements relating to future actions; prospective products, applications, customers, and technologies; future performance or results of any products; anticipated expenses; and future financial results. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from our historical experience and our present expectations or projections. Factors that could cause actual results to differ materially from those discussed in the forward-looking statements include, but are not limited to:

● our limited cash, history of losses, and our expectation that we will continue to experience operating losses and negative cash flows in the near future;

● our ability to successfully develop and implement our technologies and achieve profitability;

● our limited operating history;

● our ability to maintain the listing of our common stock on the Nasdaq Capital Market ("Nasdaq");

● changes in government regulations that could substantially reduce, or even eliminate, the need for our technology;

● emerging competition and rapidly advancing technology in our industry that may outpace our technology;

● customer demand for the products and services we develop;

● the impact of competitive or alternative products, technologies, and pricing;

● our ability to manufacture any products we design;

● general economic conditions and events and the impact they may have on us and our potential customers;

● the impact of global supply-chain constraints and the threat of, or implementation of, tariffs on imported or exported goods and materials may adversely affect our commercialization efforts and business operations;

● our revenue has been highly concentrated among a small number or customers, and our results of operations could be harmed if we lose a key revenue source and fail to replace it;

● the impact of a cybersecurity incident or other technology disruption;

● our ability to protect our intellectual property;

● our ability to obtain adequate financing in the future;

● lawsuits and other claims by third parties or investigations by various regulatory agencies that we may be subjected to;

● our ability to retain and hire personnel with the experience and talent to develop our products and business;

● our success at managing the risks involved in the foregoing items; and

● other factors discussed in this report and in the section titled "Risk Factors" in our most recent Annual Report on Form 10-K.

Forward-looking statements may appear throughout this report, including, without limitation, Item 2 "Management's Discussion and Analysis of Financial Condition and Results of Operations." The forward-looking statements are based upon management's beliefs and assumptions and are made as of the date of this report. We undertake no obligation to publicly update or revise any forward-looking statements included in this report. You should not place undue reliance on these forward-looking statements.

Unless otherwise stated or the context otherwise requires, the terms "ClearSign," "we," "us," "our" and the "Company" refer to ClearSign Technologies Corporation and its subsidiary, ClearSign Asia Limited.

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#### ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS
*The following discussion and analysis of our financial condition and results of operations should be read in conjunction with the unaudited consolidated condensed financial statements and related notes included elsewhere in this Form 10-Q as well as our audited consolidated financial statements and related notes included in our most recent Annual Report on Form 10-K. In addition to historical information, this discussion and analysis here and throughout this Form 10-Q contains forward-looking statements that involve risks, uncertainties, and assumptions. Our actual results may differ materially from those anticipated in these forward-looking statements due to a number of factors, including but not limited to, the risks described in the section titled "Risk Factors" in our Annual Report on Form 10-K for the year ended December 31, 2024.*

**Overview**

We design and develop technologies for the purpose of decarbonization and improving key performance characteristics of combustion systems, including emission and operational performance, energy efficiency and overall cost-effectiveness. Our ClearSign Core™ technology has been proven in full scale industrial test furnaces and boilers and first customer installations are currently operating in normal commercial applications. We have generated nominal revenues from operations to date to meet operating expenses.

We have incurred losses since inception totaling $104.2 million and we expect to experience operating losses and negative cash flow for the foreseeable future. We have historically financed our operations primarily through issuances of equity securities. As of September 30, 2025, we have raised approximately $105.3 million in gross proceeds through the sale of our equity securities. We may need to raise additional capital in the future, however, the significant volatility in the capital markets may negatively affect our ability to raise this additional capital.

In order to generate meaningful revenues, our technologies must gain market recognition and acceptance to develop sufficient recurring sales. In addition, management believes that the successful growth and operation of our business is dependent upon our ability to obtain adequate sources of funding through co-development agreements, strategic partnering agreements, or equity or debt financing to support commercialization of our research and development efforts, protect intellectual property, form relationships with strategic partners and provide for working capital and general corporate purposes. There can be no assurance that we will be successful in achieving our long term plans, or that such plans, if consummated, will result in profitable operations or enable us to continue in the long term as a going concern.

Our costs include employee salaries and benefits, compensation paid to consultants, materials and supplies for prototype development and manufacture, costs associated with development activities including materials, sub-contractors, travel and administration, legal and accounting expenses, sales and marketing costs, general and administrative expenses, and other costs associated with an early stage, publicly traded technology company. We currently have 16 full-time employees. Because using third party expertise and resources is more efficient than maintaining full time resources, we also expect to incur ongoing consulting expenses related to technology development and some administrative, sales and legal functions commensurate with our current level of activities.

The amount that we spend for any specific purpose may vary significantly, and could depend on a number of factors including, but not limited to, the pace of progress of our commercialization and development efforts, actual needs with respect to product testing, development and research, market conditions, and changes in or revisions to our sales and marketing strategies.

Research, development, and commercial acceptance of new technologies are, by their nature, unpredictable. Although we undertake development and commercialization efforts with reasonable diligence, there can be no assurance that the net proceeds from our securities offerings will be sufficient to enable us to develop our technology to the extent needed to create sufficient future sales to sustain operations. If the net proceeds from these offerings are insufficient for this purpose, we will consider other options to continue our path to commercialization,

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including, but not limited to, additional financing through follow-on equity offerings, debt financing, co-development agreements, sale or licensing of developed intellectual or other property, or other alternatives.

We cannot assure that our technologies will be accepted, that we will ever earn revenues sufficient to support our operations, or that we will ever be profitable. Furthermore, we have no committed source of financing, and we cannot assure that we will be able to raise money as and when we need it to continue our operations. If we cannot raise funds as and when we need them, we may be required to scale back our development by reducing expenditures for employees, consultants, business development and marketing efforts or to otherwise severely curtail, or even to cease, our operations.

**Recent Developments**

***Special Committee and Cooperation Agreements***

On February 10, 2025, the Company's board of directors (the "Board") formed a special committee of all of its then-serving independent directors (the "Special Committee") to review and analyze purported director nominations by certain of our stockholders, and non-stockholders, in connection with the Company's 2025 annual meeting of stockholders (the "2025 Annual Meeting"), and to manage communications and to negotiate and agree settlements with such purported nominating individuals. As a result of such review and analysis, the Special Committee entered into that certain Cooperation Agreement, dated May 22, 2025 (the "DiGiandomenico Cooperation Agreement"), between us and Anthony DiGiandomenico (collectively with his affiliates and associates, the "DiGiandomenico Parties"), and that certain Cooperation Agreement, dated May 22, 2025 (the "Clarkson Cooperation Agreement," and together with the DiGiandomenico Cooperation Agreement, the "Cooperation Agreements"), between us and Richard Clarkson (collectively with his affiliates and associates, the "Clarkson Parties"), which agreements required, among other things, the appointment of Mr. DiGiandomenico and Louis J. Basenese to the Board. Accordingly, the Board increased its size from five to seven directors, appointed Messrs. DiGiandomenico and Basenese to the Board, and nominated each such director as a candidate for election to the Board at the 2025 Annual Meeting. Following the 2025 Annual Meeting, the Special Committee was dissolved.

***At The Market Agreement with H.C. Wainwright***

On July 17, 2025, we entered into an ATM Offering Agreement (the "ATM Agreement") with Wainwright. In accordance with the terms of the ATM Agreement, we may offer and sell from time to time through Wainwright, acting as sales agent, shares of our common stock having an aggregate offering price of up to $10,390,000 (the "Placement Shares"). The Placement Shares will be issued pursuant to our "shelf" registration statement on Form S-3 (File No. 333-288736) filed with the SEC on July 17, 2025 (the "Registration Statement") and the prospectus relating to the offer and sale of the Placement Shares that forms a part of the Registration Statement, which was declared effective on July 28, 2025.

***Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard***

On April 1, 2025, we received a letter (the "Notice") from Nasdaq's Listing Qualifications Staff (the "Staff") indicating that, based upon the closing bid price of our common stock for the 30 consecutive business days beginning on February 18, 2025, and ending on March 31, 2025, we no longer meet the requirement to maintain a minimum bid price of $1 per share, as set forth in Nasdaq Listing Rule 5550(a)(2) (the "Bid Price Rule").

On September 30, 2025, we received a second letter from Nasdaq granting our request for a 180-day extension to regain compliance with the Bid Price Rule. We now have until March 30, 2026, to meet the requirement. As part of our request for the 180-day extension, we notified Nasdaq that we intend to regain compliance with the Bid Price Rule by effecting a reverse stock split, if necessary. If at any time prior to March 30, 2026, the bid price of our common stock closes at $1 per share or more for a minimum of 10 consecutive business days, we will regain compliance with the Bid Price Rule.

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If the Company does not regain compliance with the Bid Price Rule during the additional 180-day extension, Nasdaq will provide written notification to us that our common stock will be delisted. At that time, we may appeal the relevant delisting determination to a hearings panel pursuant to the procedures set forth in the applicable Nasdaq Listing Rules. However, there can be no assurance that, if we appeal the delisting determination by Nasdaq to the hearings panel, that such appeal would be successful.

We will continue to monitor the closing bid price of our common stock and evaluate its available options to regain compliance with the Bid Price Rule. Nasdaq's extension notice has no immediate effect on the listing or trading of our common stock, which continues to trade on Nasdaq under the ticker symbol "CLIR."

**Critical Accounting Policies**

The following discussion and analysis of financial condition and results of operations is based upon our condensed consolidated financial statements, which have been prepared in conformity with accounting principles generally accepted in the United States. Certain accounting policies and estimates are particularly important to the understanding of our financial position and results of operations. These policies and estimates require the application of significant judgment by management. These estimates can be materially affected by changes from period to period as economic factors and conditions outside of our control change. As a result, they are subject to an inherent degree of uncertainty. In applying these policies, our management uses their judgment to determine the appropriate assumptions to be used in the determination of certain estimates. Those estimates are based on our historical operations, our future business plans and projected financial results, the terms of existing contracts, our observance of trends in the industry, information provided by our customers and information available from other outside sources, as appropriate. We believe the current assumptions and other considerations used to estimate amounts reflected in the condensed consolidated financial statements included in this Form 10-Q are appropriate.

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This Form 10-Q and our most recent Annual Report on Form 10-K include discussions of our accounting policies, as well as methods and estimates used in the preparation of our audited consolidated financial statements. For further information on our critical accounting policies and estimates, see "Item 7 – Management's Discussion and Analysis of Financial Condition and Results of Operations" in our most recent Annual Report on Form 10-K, the notes to our audited consolidated financial statements included in our most recent Annual Report on Form 10-K and "Note 2 – Summary of Significant Accounting Policies" of our unaudited condensed consolidated financial statements included elsewhere in this Form 10-Q. Since our most recent Annual Report on Form 10-K, we have not experienced a material change to our critical accounting policies or the methods and applications used to develop our accounting estimates.

**Results of Operations**

**Comparison of the Three and Nine Months Ended September 30, 2025 and 2024**

Highlights of our quarter financial performance are as follows:

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| | | | | |
|:---|:---|:---|:---|:---|
|  | **For the Three Months Ended**  | **For the Three Months Ended**  |  |  |
| (in thousands, except per share data) | **September 30,**  | **September 30,**  |  |  |
|  | **2025** | **2024** | **$ Change** | **% Change** |
| Revenues | $1029 | $1859 | $(830) | (44.6)% |
| Cost of goods sold | 661 | 1308 | $(647) | (49.5)% |
| Gross profit | 368 | 551 | $(183) | (33.2)% |
| &nbsp;&nbsp;Research and development | 310 | 329 | $(19) | (5.8)% |
| &nbsp;&nbsp;General and administrative | 1808 | 1655 | $153 | 9.2% |
| Operating expenses | 2118 | 1984 | $134 | 6.8% |
| Other income, net | 321 | 278 | $43 | 15.5% |
| Net loss | $(1429) | $(1155) | $(274) | (23.7)% |
| Basic and diluted net loss per common share | $(0.03) | $(0.02) | $(0.01) | (50.0)% |

---

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| | | | | |
|:---|:---|:---|:---|:---|
|  | **For the Nine Months Ended**  | **For the Nine Months Ended**  |  |  |
| (in thousands, except per share data) | **September 30,**  | **September 30,**  |  |  |
|  | **2025** | **2024** | **$ Change** | **% Change** |
| Revenues | $1563 | $3006 | $(1443) | (48.0)% |
| Cost of goods sold | 944 | 1976 | $(1032) | (52.2)% |
| Gross profit | 619 | 1030 | $(411) | (39.9)% |
| &nbsp;&nbsp;Research and development | 1004 | 1012 | $(8) | (0.8)% |
| &nbsp;&nbsp;General and administrative | 5460 | 4840 | $620 | 12.8% |
| Operating expenses | 6464 | 5852 | $612 | 10.5% |
| Other income, net | 660 | 687 | $(27) | (3.9)% |
| Net loss | $(5185) | $(4135) | $(1050) | (25.4)% |
| Basic and diluted net loss per common share | $(0.09) | $(0.09) |  |  |

---

*Revenues and Gross Profit*

Consolidated revenues for the three months ended September 30, 2025 were $1,029 thousand compared to $1,859 thousand for the same period in 2024, which were predominantly generated by delivering spare parts to multiple customers, delivering a flare order, delivering a mid-stream order, completing a customer witness test, finalizing a CFD analysis, and providing engineering services. Revenues for the three months ended September 30, 2024 were predominantly generated by shipping multiple burners to a California refinery customer.

Consolidated revenues for the nine months ended September 30, 2025 were $1,563 thousand compared to $3,006 thousand for the same period in 2024, which were predominantly generated by delivering spare parts orders to multiple customers, delivering a flare order, delivering mid-stream orders, and completing engineering services and a CFD analysis. Revenues for the nine months ended September 30, 2024 were predominantly generated from by delivering multiple burners, performing engineering feasibility studies, and delivering multiple spare parts orders.

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Gross profit decreased by $183 thousand, or 33.2%, and by $411 thousand, or 39.9%, for the three and nine months ended September 30, 2025, respectively, compared to the same time periods in 2024. The unfavorable decrease in gross profit for the three months ended September 30, 2025 was predominantly due to lower revenues during the three months ended September 30, 2025. This decrease was partially offset by a $63 thousand increase in profit margin, which was predominantly due to the higher profit margin related to our spare parts orders during three months ended September 30, 2025 compared to the profit margin for the products and services that generated revenues during the same period in 2024. The unfavorable decrease in gross profit for the nine months ended September 30, 2025 was predominantly due to lower revenues during the nine months ended September 30, 2025. This decrease was partially offset by a $83 thousand increase in profit margin, which was predominantly due to the higher profit margin related to our spare parts orders during nine months ended September 30, 2025 compared to the profit margin for the products and services that generated revenues during the same period in 2024.

*Operating Expenses*

Operating expenses consist of research and development ("R&D") and general and administrative ("G&A") expenses. These are addressed separately below.

*Research and Development*

R&D expenses remained relatively consistent year-over-year for both the three and nine months ended September 30, 2025 respectively, compared to the same time periods in 2024.

*General and Administrative*

G&A expenses increased $153 thousand, or 9.3%, for the three months ended September 30, 2025, compared to the same time period in 2024. We experienced an increase of approximately $729 thousand in non-cash expenses for the vesting of RSUs in connection with the departure of three directors from the Board. Legal and audit expenses also increased by approximately $205 thousand related to services provided for the filing of our "shelf" registration statement on Form S-3 and ATM Agreement with Wainwright. Increases in G&A expenses were partially offset by a year-over-year savings of $394 thousand as a result of a decrease in costs accrued related to the suspension of our China activities that occurred during the three months ended September 30, 2024, which did not occur during the same period in 2025. We also decreased our Special Committee legal cost accrual by $315 thousand after negotiating discounts with law firms engaged by the Special Committee (see "Recent Developments – Special Committee and Cooperation Agreements" above for additional information). G&A expense increases were further partially offset by year-over-year labor and overhead cost decreases of $127 thousand related to customer contract work performed during the three months ended September 30, 2025.

G&A expenses for the nine months ended September 30, 2025 increased by $620 thousand, or 12.8%, compared to the same period in 2024. This unfavorable increase in G&A expenses was primarily due to an increase of approximately $588 thousand in legal fees, including (i) approximately $131 thousand in legal fees pertaining to work performed in connection with a regulatory inquiry by the SEC into the trading of our securities in 2020; (ii) an accrual of approximately $435 thousand in legal fees pertaining to work performed for the Special Committee; and (iii) an accrual of $22 thousand for the reimbursement of certain legal fees incurred by the Clarkson Parties and DiGiandomenico Parties in connection with the Cooperation Agreements they entered into with us (see "Recent Developments – Special Committee and Cooperation Agreements" above for additional information). We also incurred an increase in legal and audit costs of approximately $205 thousand related to services provided for the preparation and filing of our "shelf" registration statement on Form S-3 and work performed in connection with our ATM Agreement with Wainwright. In addition, non-cash expenses increased approximately $469 thousand year-over-year related to the vesting of RSUs in connection with the departure of three directors from the Board. Increases in G&A expenses for the nine months ended September 30, 2025 were partially offset by an expense decrease of approximately $394 thousand related to our China exit cost accrual that occurred during the three months ended September 30, 2024, which did not occur during the same

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period in 2025. G&A expense increases were further partially offset by year-over-year labor and overhead cost decreases of $232 thousand related to customer contract work performed during the nine months ended September 30, 2025.

*Other Income, Net*

Other income, net remained relatively consistent year-over-year for both the three and nine months ended September 30, 2025 respectively, compared to the same time periods in 2024.

**Liquidity and Capital Resources**

At September 30, 2025, our cash and cash equivalents balance totaled $10,488 thousand compared to $14,035 thousand at December 31, 2024, a decrease of $3,547 thousand. The decrease in cash and cash equivalent balance is primarily attributable to our net loss of $5,185 thousand which was partially offset by our non-cash expenses of $1,135 thousand and an increase in contract liabilities of $1,075 thousand.

At September 30, 2025, our current assets were in excess of current liabilities resulting in working capital of $8,168 thousand compared to $12,809 thousand at December 31, 2024. We believe we have sufficient cash and expected cash collections to fund current operating expenses for over twelve months. We have no contractual debt obligations and to the extent we may require additional funds beyond twelve months from the date hereof, and customer cash collections cannot fund our needs, we may utilize equity offerings. Historically, we have funded operations predominantly through equity offerings. Until the growth of revenue increases to a level that covers our operating expenses, we intend to continue to fund operations in this manner, although the volatility in the capital markets may negatively affect our ability to do so. As of September 30, 2025, approximately 21.3 million shares of our common stock are issuable upon exercise of our outstanding warrants, which number excludes the shares of common stock issuable upon exercise of our outstanding pre-funded warrants, and we may receive up to $22.5 million in aggregate gross proceeds from the cash exercises thereof, subject to certain beneficial ownership limitations set forth therein. These warrants require the warrant holder to tender cash upon exercise, with the exception of the warrants issued to Public Ventures LLC as compensation for their services in connection with our public offering and concurrent private placement in April 2024, which allow the holder to exercise cashless if they so desire. These equity financial instruments may from time-to-time fund future cash needs, but the volatility of our common stock price and the risk tolerance of warrant holders will determine the extent in which we will be able to raise funds in this manner.

Operating activities for the nine months ended September 30, 2025, resulted in cash outflows of $3,453 thousand, primarily due to the net loss of $5,185 thousand partially offset by non-cash expenses of $1,135 thousand and an increase in contract liabilities of $1,075 thousand during such period. The change in contract liabilities during the nine months ended September 30, 2025 was impacted by customer collections for orders we have yet to complete.

Operating activities for the nine months ended September 30, 2024, resulted in cash outflows of $3,958 thousand, primarily due to the net loss of $4,135 thousand during such period, which was partially offset by a non-cash expense of $688 thousand. The decision to suspend our China operations increased accounts payable and accrued liabilities by $394 thousand during the three months ended September 30, 2024, which represented a one-time accrual estimate for the costs to prepare and place our Beijing China entity into a dormant state.

Investing activities for the nine months ended September 30, 2025, resulted in cash outflows of $78 thousand, which is primarily attributable to disbursements for patents and other intangible assets.

Investing activities for the nine months ended September 30, 2024, resulted in cash outflows of $177 thousand, which is primarily attributable to $159 thousand of disbursements for patents and other intangible assets.

Financing activities for the nine months ended September 30, 2025, resulted in cash outflows of $17 thousand, which is primarily attributable to $41 thousand of disbursements related to taxes paid for the vesting of certain employee restricted stock units, partially offset by $24 thousand in net proceeds received from the exercise of our warrants.

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Financing activities for the nine months ended September 30, 2024, resulted in cash inflows of $12,936 thousand, which is primarily attributable to the net proceeds received of $12,967 thousand from the issuance of securities in connection with our 2024 equity offerings.

**Off-Balance Sheet Transactions**

We do not have any off-balance sheet transactions.

#### ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK
As a smaller reporting company, we are not required to provide this information.

#### ITEM 4. CONTROLS AND PROCEDURES
**Disclosure Controls and Procedures**

We maintain disclosure controls and procedures, as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act, that are designed to reasonably ensure that information required to be disclosed in our reports filed under the Exchange Act, is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission's rules and forms, and that such information is accumulated and communicated to our management, including our principal executive officer and principal accounting and financial officer, as appropriate, to allow timely decisions regarding required disclosure.

We carried out an evaluation under the supervision and with the participation of management, including our Chief Executive Officer (principal executive officer) and our Chief Financial Officer (principal accounting and financial officer), of the effectiveness of the design and operation of our disclosure controls and procedures as of September 30, 2025, the end of the period covered by this Form 10-Q. Based upon the evaluation of our disclosure controls and procedures as of September 30, 2025, our Chief Executive Officer (principal executive officer) and our Chief Financial Officer (principal accounting and financial officer) concluded that, as of such date, our disclosure controls and procedures were effective at the reasonable assurance level.

**Changes in Internal Control over Financial Reporting**

There have been no changes in our internal control over financial reporting that occurred during the quarter ended September 30, 2025 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

**Limitations on Effectiveness of Controls and Procedures**

Our management, including our Chief Executive Officer (principal executive officer) and our Chief Financial Officer (principal accounting and financial officer), does not expect that our disclosure controls and procedures or our internal control over financial reporting will prevent or detect all errors and all fraud. A control system, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control system are met. Further, the design of a control system must reflect the fact that there are resource constraints, and the benefits of controls must be considered relative to their costs. Because of the inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that all control issues and instances of fraud, if any, have been detected. These inherent limitations include the realities that judgments in decision making can be faulty, and that breakdowns can occur because of a simple error or mistake. Additionally, controls can be circumvented by the individual acts of some persons, by collusion of two or more people or by management override of the controls. The design of any system of controls is also based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions. Over time, controls may become inadequate because of changes in conditions, or the degree of compliance with policies or

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procedures. Because of the inherent limitations in a cost-effective control system, misstatements due to error or fraud may occur and not be detected.

#### PART II - OTHER INFORMATION

#### ITEM 1. LEGAL PROCEEDINGS
From time to time, we may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. However, litigation is subject to inherent uncertainties and an adverse result in these or other matters may arise from time to time that may harm our business. We are currently not aware of any such legal proceedings or claims that we believe will have a material adverse effect on our business, financial condition or operating results.

#### ITEM 1A. RISK FACTORS
We incorporate herein by reference the risk factors included under "Part I - Item 1A. Risk Factors" of our Annual Report on Form 10-K for the year ended December 31, 2024 which we filed with the SEC on March 31, 2025. There are no material changes from the risk factors set forth in such prior filing, except as set forth below.

***Our ability to utilize our common stock to finance future capital needs, or for other purposes, is limited by the number of authorized shares of common stock currently available for issuance.***

We have authority to issue a total of 87,500,000 shares of common stock, of which 53,273,405 shares of common stock have been issued and approximately 30,000,000 shares of common stock are reserved for issuance in connection with certain securities issued under our equity incentive plans and other outstanding securities, including stock options and warrants.

We have historically financed our operations primarily through issuances of equity securities. With the limited shares of common stock presently available for issuance, our ability to secure additional financing through the sale of common stock, to the extent needed, is limited. Absent an increase in the shares of common stock authorized to be issued under our certificate of incorporation, we will be limited to other financing structures in the event additional financing is required. Such alternative structures may be less favorable or unavailable in which case we may be forced to forego opportunities or required to downsize operations due to lack of funding.

***If we fail to comply with Nasdaq's continued minimum closing bid requirements by March 30, 2026 or other requirements for continued listing, including stockholder equity requirements, our common stock may be delisted and the price of our common stock and our ability to access the capital markets could be negatively impacted.***

Our common stock is listed for trading on Nasdaq, therefore, we must satisfy Nasdaq's continued listing requirements, including, among other things, a minimum closing bid price requirement of $1.00 per share for 30 consecutive business days, which is referred to as the Bid Price Rule. On April 1, 2025, the Staff notified us that we did not comply with the Bid Price Rule, as set forth in Nasdaq Listing Rule 5550(a)(2), during the 30 consecutive business day period beginning on February 18, 2025, and ending March 31, 2025. We were granted 180 calendar days, or until September 29, 2025, to regain compliance with the Bid Price Rule.

On September 30, 2025, the Staff sent us a second letter granting our request for a 180-day extension, or until March 30, 2026, to regain compliance with the Bid Price Rule. To regain compliance with the Bid Price Rule and to qualify for continued listing on Nasdaq, the minimum bid price per share of our common stock must be at least $1.00 for at least ten consecutive business days during the 180-day extension. As part of our request for the 180-day extension, we notified Nasdaq that we intend to regain compliance with the Bid Price Rule by effecting a reverse stock split, if necessary. If we do not regain compliance with the Bid Price Rule during the 180-day extension, our common stock will be subject to delisting by Nasdaq. At that time, we may appeal the relevant delisting determination to a hearings panel

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pursuant to the procedures set forth in the applicable Nasdaq Listing Rules. However, there can be no assurance that, if the we do appeal the delisting determination by Nasdaq to the hearings panel, that such appeal would be successful.

There can be no assurance that we will be able to regain compliance with Nasdaq's listing rules, including the Bid Price Rule. If we are unable to regain compliance with the Bid Price Rule or if we fail to meet any of the other continued listing requirements, including stockholder equity requirements, our securities may be delisted from Nasdaq, which could reduce the liquidity of our common stock materially and result in a corresponding material reduction in the price of our common stock. In addition, delisting could harm our ability to raise capital on terms acceptable to us, or at all, and may result in the potential loss of confidence by investors, employees and business development opportunities.

***Adverse judgments or settlements in legal proceedings could materially harm our business, financial condition, operating results and cash flows.***

We may be a party to claims that arise from time to time in the ordinary course of our business, which may include those related to, for example, our securities offerings, contracts, sub-contracts, protection of confidential information or trade secrets, adversary proceedings arising from customer bankruptcies, stockholder engagement, employment of our workforce and immigration requirements or compliance with any of a wide array of state and federal statutes, rules and regulations that pertain to different aspects of our business.

Regardless of the merits of any particular claim, responding to such actions could divert time, resources and management's attention away from our business operations, and we may incur significant expenses in defending these lawsuits or other similar lawsuits. The results of litigation and other legal proceedings are inherently uncertain, and adverse judgments or settlements in some of these legal disputes may result in adverse monetary damages, penalties or injunctive relief against us, which could have a material adverse effect on our financial condition, operating results and cash flows. Any claims or litigation, even if fully indemnified or insured, could damage our reputation and make it more difficult to compete effectively or to obtain adequate insurance in the future.

Furthermore, while we maintain insurance for certain potential liabilities, such insurance does not cover all types and amounts of potential liabilities and is subject to various exclusions as well as deductibles and caps on amounts of coverage. Even if we believe a claim is covered by insurance, insurers may dispute our entitlement to coverage for a variety of potential reasons, which may affect the timing and, if the insurers prevail, the amount of our available insurance coverage for a particular claim. Further, whether or not we are named as a party to a particular proceeding or threatened proceeding, we may be subject to indemnification and/or advancement obligations to our current directors and executive officers as well as other third parties, which may include former directors, that could subject us to liability for damages or other amounts payable as a result of any judgments or settlements, as well as for fees and expenses incurred in connection with any proceedings or threatened proceedings.

We may also be required to initiate expensive litigation or other proceedings to protect our business interests. There is a risk that we will not be successful or otherwise be able to satisfactorily resolve such claims or litigation. Litigation and other legal claims are subject to inherent uncertainties. Those uncertainties include, but are not limited to, litigation costs and attorneys' fees, unpredictable judicial or jury decisions and the differing laws and judicial proclivities regarding damage awards among the states in which we operate. Unexpected outcomes in such legal proceedings, or changes in management's evaluation or predictions of the likely outcomes of such proceedings, could have a material adverse effect on our business, financial condition, results of operations and cash flows. Our current financial status may increase our default and litigation risks and may make us more financially vulnerable in the face of threatened litigation.

#### ITEM 2. UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS
On November 13, 2024, the Board authorized issuance of 15,000 shares to be remitted in quarterly installments to our investor relations firm, Firm IR Group LLC ("Firm IR"), for services rendered by them, pursuant to our 2013 Consultant Stock Plan. On September 30, 2025, we issued 3,750 shares of common stock to Firm IR at a fair market value price per share of $0.94, the closing price of our common stock as reported on Nasdaq on November 13, 2024, the date of grant. Additionally, on August 26, 2025, we issued 87,016 shares of common stock to Firm IR at a fair market

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value price per share of $0.58 for reimbursement of certain legal fees incurred by Firm IR in connection with services provided as our investor relations service provider. These shares were issued in reliance upon the exemption from registration provided by Section 4(a)(2) of the Securities Act, for a transaction by an issuer not involving a public offering.

#### ITEM 3. DEFAULTS UPON SENIOR SECURITIES
Not applicable.

#### ITEM 4. MINE SAFETY DISCLOSURES
Not applicable.

**ITEM 5.** **OTHER INFORMATION**

**Anthony DiGiandomenico Appointment to Nominating and Corporate Governance Committee**

The information included in this "Part II – Item 5. Other Information" of this Form 10-Q is provided in lieu of filing such information on a Current Report on Form 8-K under "Item 8.01. Other Events."

On November 11, 2025, upon recommendation from the Nominating and Corporate Governance Committee of the Board (the "Governance Committee"), the Board appointed Anthony DiGiandomenico to the Governance Committee as its chairperson, effective immediately. As a result of such change, the current composition of the Board committees is as follows:

Audit and Risk Committee:

● G. Todd Silva, Chairperson

● Louis J. Basenese

● Anthony DiGiandomenico

Human Capital and Compensation Committee:

● Louis J. Basenese, Chairperson

● G. Todd Silva

Nominating and Corporate Governance Committee:

● Anthony DiGiandomenico, Chairperson

● Louis J. Basenese

● G. Todd Silva

**Director or Executive Officer Rule 10b5-1(c) Trading Plans**

None of the Company's directors or officers adopted, modified or terminated a Rule 10b-5 trading arrangement or a non-Rule 10b-5 trading arrangement during the fiscal quarter ended September 30, 2025, as such terms are defined under Item 408(a) of Regulation S-K.

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| | |
|:---|:---|
| &nbsp;&nbsp;**Item 6.**<br>**Exhibit** | &nbsp;&nbsp;**EXHIBITS**<br>|
| &nbsp;&nbsp;**Number** | &nbsp;&nbsp;**Document** |
| &nbsp;&nbsp;3.1 | &nbsp;&nbsp;[Certificate of Incorporation of ClearSign Technologies Corporation, a Delaware corporation (incorporated by reference to Exhibit 3.3 of the Company's Form 8-K filed with the Securities and Exchange Commission on June 15, 2023).](https://www.sec.gov/Archives/edgar/data/1434524/000110465923071426/tm2318661d1_ex3-3.htm) |
| &nbsp;&nbsp;3.2 | &nbsp;&nbsp;[Certificate of Amendment, as filed with the Secretary of the State of Delaware on June 25, 2024 (incorporated by reference to Exhibit 3.1 of the Company's Form 8-K filed with the Securities and Exchange Commission on June 26, 2024).](https://www.sec.gov/Archives/edgar/data/1434524/000110465924075194/tm2418248d1_ex3-1.htm) |
| &nbsp;&nbsp;3.3 | &nbsp;&nbsp;[Bylaws of ClearSign Technologies Corporation, a Delaware corporation (incorporated by reference to Exhibit 3.4 of the Company's Form 8-K filed with the Securities and Exchange Commission on June 15, 2023).](https://www.sec.gov/Archives/edgar/data/0001434524/000110465923071426/tm2318661d1_ex3-4.htm)<br>|
| &nbsp;&nbsp;4.1 | &nbsp;&nbsp;[Form of Common Warrant (incorporated by reference to Exhibit 4.1 of the Company's Form 8-K filed with the Securities and Exchange Commission on April 19, 2024)](https://www.sec.gov/Archives/edgar/data/1434524/000110465924049160/tm2412212d1_ex4-1.htm). |
| &nbsp;&nbsp;4.2 | &nbsp;&nbsp;[Form of Underwriter's Warrant (incorporated by reference to Exhibit 4.2 of the Company's Form 8-K filed with the Securities and Exchange Commission on April 19, 2024).](https://www.sec.gov/Archives/edgar/data/1434524/000110465924049160/tm2412212d1_ex4-2.htm) |
| &nbsp;&nbsp;4.3 | &nbsp;&nbsp;[Form of Private Warrant (incorporated by reference to Exhibit 4.3 of the Company's Form 8-K filed with the Securities and Exchange Commission on April 19, 2024).](https://www.sec.gov/Archives/edgar/data/1434524/000110465924049160/tm2412212d1_ex4-3.htm) |
| &nbsp;&nbsp;4.4 | &nbsp;&nbsp;[Form of Pre-Funded Warrant (incorporated by reference to Exhibit 4.1 of the Company's Form 8-K filed with the Securities and Exchange Commission on April 23, 2024).](https://www.sec.gov/Archives/edgar/data/1434524/000110465924050306/tm2412465d1_ex4-1.htm) |
| &nbsp;&nbsp;4.5 | &nbsp;&nbsp;[Form of Placement Agent Warrant (incorporated by reference to Exhibit 4.4 of the Company's Form 8-K filed with the Securities and Exchange Commission on April 19, 2024).](https://www.sec.gov/Archives/edgar/data/1434524/000110465924049160/tm2412212d1_ex4-4.htm) |
| &nbsp;&nbsp;31.1\* | &nbsp;&nbsp;[Rule 13a-14(a)/15d-14(a) Certification of Principal Executive Officer](clir-20250930xex31d1.htm). |
| &nbsp;&nbsp;31.2\* | &nbsp;&nbsp;[Rule 13a-14(a)/15d-14(a) Certification of Principal Financial Officer](clir-20250930xex31d2.htm). |
| &nbsp;&nbsp;32.1\*\* | &nbsp;&nbsp;[Section 1350 Certification of Principal Executive Officer and Principal Financial Officer](clir-20250930xex32d1.htm). |
| &nbsp;&nbsp;101.INS\* | &nbsp;&nbsp;Inline XBRL Instance Document. |
| &nbsp;&nbsp;101.SCH\* | &nbsp;&nbsp;Inline XBRL Taxonomy Extension Schema Document. |
| &nbsp;&nbsp;101.CAL\* | &nbsp;&nbsp;Inline XBRL Taxonomy Extension Calculation Linkbase Document. |
| &nbsp;&nbsp;101.DEF\* | &nbsp;&nbsp;Inline XBRL Taxonomy Extension Definition Linkbase Document. |
| &nbsp;&nbsp;101.LAB\* | &nbsp;&nbsp;Inline XBRL Taxonomy Extension Label Linkbase Document. |
| &nbsp;&nbsp;101.PRE\* | &nbsp;&nbsp;Inline XBRL Taxonomy Extension Presentation Linkbase Document. |
| &nbsp;&nbsp;104\* | &nbsp;&nbsp;Cover Page Interactive Data File (formatted as inline XBRL and contained in Exhibit 101). |

---

\*Filed herewith.

\*\*Furnished herewith.

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

---

| | | |
|:---|:---|:---|
|  |  | **CLEARSIGN TECHNOLOGIES CORPORATION** |
| Date: November 14, 2025 | By: | /s/ Colin James Deller |
|  |  | Colin James Deller |
|  |  | Chief Executive Officer  |
|  |  | (Principal Executive Officer) |

---

---

| | | |
|:---|:---|:---|
| Date: November 14, 2025 | By: | /s/ Brent Hinds |
|  |  | Brent Hinds |
|  |  | Chief Financial Officer<br>(Principal Financial and Accounting Officer) |

---

## Exhibit 31.1

**Exhibit 31.1**

**CERTIFICATION**

I, Colin James Deller, certify that:

&nbsp;&nbsp;&nbsp;&nbsp;1. I have reviewed this quarterly report on Form 10-Q of ClearSign Technologies Corporation;

&nbsp;&nbsp;&nbsp;&nbsp;2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

&nbsp;&nbsp;&nbsp;&nbsp;3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

&nbsp;&nbsp;&nbsp;&nbsp;4. The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15-d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including any consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting;

&nbsp;&nbsp;&nbsp;&nbsp;5. The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

---

| |
|:---|
| Date: November 14, 2025 |
| */s/ Colin James Deller* |
| Colin James Deller |
| Chief Executive Officer |
| (*Principal Executive Officer*) |

---

------

## Exhibit 31.2

**Exhibit 31.2**

**CERTIFICATION**

I, Brent Hinds, certify that:

&nbsp;&nbsp;&nbsp;&nbsp;1. I have reviewed this quarterly report on Form 10-Q of ClearSign Technologies Corporation;

&nbsp;&nbsp;&nbsp;&nbsp;2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

&nbsp;&nbsp;&nbsp;&nbsp;3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

&nbsp;&nbsp;&nbsp;&nbsp;4. The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15-d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including any consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting;

&nbsp;&nbsp;&nbsp;&nbsp;5. The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

---

| |
|:---|
| Date: November 14, 2025 |
| */s/ Brent Hinds* |
| Brent Hinds |
| Chief Financial Officer |
| (*Principal Financial and Accounting Officer*) |

---

------

## Exhibit 32.1

**Exhibit 32.1**

**CERTIFICATION**

In connection with the quarterly report on Form 10-Q of ClearSign Technologies Corporation (the "Company") for the period ended September 30, 2025 as filed with the Securities and Exchange Commission (the "Report"), we, Colin James Deller, Chief Executive Officer (Principal Executive Officer) and Brent Hinds, Chief Financial Officer (Principal Financial and Accounting Officer) of the Company, hereby certify as of the date hereof, solely for purposes of Rule 13a-14(b) of the Securities Exchange Act of 1934, as amended (the "Exchange Act") and Title 18, Chapter 63, Section 1350 of the United States Code, that to the best of my knowledge:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(1) The Report fully complies with the requirements of Section 13(a) or 15(d), as applicable, of the Exchange Act, and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company at the dates and for the periods indicated.

---

| |
|:---|
| Date: November 14, 2025 |
| /s/ Colin James Deller |
| Colin James Deller |
| Chief Executive Officer |
| (*Principal Executive Officer*) |
| /s/ Brent Hinds |
| Brent Hinds |
| Chief Financial Officer <br>(*Principal Financial and Accounting Officer*) |

---

This certification accompanies the Form 10-Q to which it relates, is not deemed filed with the Securities and Exchange Commission and is not to be incorporated by reference into any filing of the Company under the Securities Act of 1933, as amended, or the Exchange Act (whether made before or after the date of the Report), irrespective of any general incorporation language contained in such filing.

------