SecProbe.io

CORRESP
 1
 filename1.htm

 August 20, 2025

 VIA EDGAR

 U.S. Securities and Exchange Commission
Division of Corporation Finance
100 F Street, N.E.
Washington, D.C. 20549

 RE:
 ClearSign Technologies Corporation

 Registration Statement on Form S-1, as amended

 Filed August 12, 2025

 File No. 333-289549

 Acceleration Request

 Requested Date: Thursday, August 21, 2025

 Requested Time: 5:00 p.m. Eastern Time

 Ladies and Gentlemen:

 In accordance with Rule 461
under the Securities Act of 1933, as amended, the undersigned registrant (the " Registrant ") hereby requests that the
Securities and Exchange Commission (the " Commission ") take appropriate action to cause the above-referenced Registration
Statement on Form S-1 (File No. 333-289549) (as amended, the " Registration Statement ") to become effective on Thursday,
August 21, 2025, at 5:00 p.m. Eastern Time, or as soon thereafter as possible, or at such later time as the Registrant or its outside
counsel, Mitchell Silberberg & Knupp LLP, may orally request via telephone call to the staff.

 Once the Registration Statement
has been declared effective, please orally confirm that event with our outside counsel by calling Blake Baron at (917) 546-7709.

 Very truly yours,

 ClearSign Technologies Corporation

 By:
 /s/ Colin James
Deller

 Colin James
Deller

 Chief Executive Officer

 cc: Gabriel Miranda, Esq., Mitchell Silberberg & Knupp LLP

 ClearSign Technologies Corporation – 8023
East 63 rd Place, Suite 101, Tulsa, Oklahoma 74133 – Tel: 206.673.4848 –

 www.clearsign.com

<DOCUMENT>
<TYPE>TEXT-EXTRACT
<SEQUENCE>2
<FILENAME>filename2.txt
<TEXT>
 August 14, 2025

Colin James Deller
Chief Executive Officer
ClearSign Technologies Corp
8023 East 63rd Place, Suite 101
Tulsa, OK 74133

 Re: ClearSign Technologies Corp
 Registration Statement on Form S-1
 Filed August 12, 2025
 File No. 333-289549
Dear Colin James Deller:

 This is to advise you that we have not reviewed and will not review your
registration
statement.

 Please refer to Rules 460 and 461 regarding requests for acceleration.
We remind you
that the company and its management are responsible for the accuracy and
adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action
by the staff.

 Please contact Margaret Sawicki at 202-551-7153 with any questions.

 Sincerely,

 Division of
Corporation Finance
 Office of Industrial
Applications and
 Services
cc: Blake Baron, Esq.
</TEXT>
</DOCUMENT>

CORRESP
 1
 filename1.htm

 July 24, 2025

 VIA EDGAR

 U.S. Securities and Exchange Commission
Division of Corporation Finance
100 F Street, N.E.
Washington, D.C. 20549

 RE: ClearSign Technologies Corporation

 Registration Statement on Form S-3

 Filed July 17, 2025

 File No. 333-288736

 Acceleration Request

 Requested Date: Monday, July 28, 2025

 Requested Time: 4:30 p.m. Eastern Time

 Ladies and Gentlemen:

 In accordance with Rule 461
under the Securities Act of 1933, as amended, the undersigned registrant (the " Registrant ") hereby requests that the
Securities and Exchange Commission (the " Commission ") take appropriate action to cause the above-referenced Registration
Statement on Form S-3 (File No. 333-288736) (the " Registration Statement ") to become effective on Monday,
July 28, 2025, at 4:30 p.m. Eastern Time, or as soon thereafter as possible, or at such later time as the Registrant or its
outside counsel, Mitchell Silberberg & Knupp LLP, may orally request via telephone call to the staff.

 Once the Registration Statement
has been declared effective, please orally confirm that event with our outside counsel by calling Blake Baron at (917) 546-7709.

 Very truly yours,

 ClearSign Technologies Corporation

 By: /s/ Colin James Deller

 Colin James Deller

 Chief Executive Officer

 cc: Gabriel Miranda, Esq., Mitchell Silberberg & Knupp
LLP

 ClearSign Technologies Corporation
 – 8023 East 63 rd Place, Suite 101, Tulsa, Oklahoma 74133 – Tel: 206.673.4848 – www.clearsign.com

<DOCUMENT>
<TYPE>TEXT-EXTRACT
<SEQUENCE>2
<FILENAME>filename2.txt
<TEXT>
 July 24, 2025

Colin Deller
Chief Executive Officer
ClearSign Technologies Corporation
8023 East 63rd Place, Suite 101
Tulsa, OK 74133

 Re: ClearSign Technologies Corporation
 Registration Statement on Form S-3
 Filed July 17, 2025
 File No. 333-288736
Dear Colin Deller:

 This is to advise you that we have not reviewed and will not review your
registration
statement.

 Please refer to Rules 460 and 461 regarding requests for acceleration.
We remind you
that the company and its management are responsible for the accuracy and
adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action
by the staff.

 Please contact Nicholas O'Leary at 202-551-4451 with any questions.

 Sincerely,

 Division of
Corporation Finance
 Office of Industrial
Applications and
 Services
cc: Blake Baron, Esq.
</TEXT>
</DOCUMENT>

November 8, 2024
Brent Hinds
Chief Financial Officer
ClearSign Technologies Corp
8023 E. 63rd Place, Suite 101
Tulsa, Oklahoma 74133
Re:ClearSign Technologies Corp
Amendment No. 1 to Form 10-K for the Year Ended December 31, 2023
File No. 001-35521
Dear Brent Hinds:
            We have completed our review of your filing. We remind you that the company and
its management are responsible for the accuracy and adequacy of their disclosures,
notwithstanding any review, comments, action or absence of action by the staff.
Sincerely,
Division of Corporation Finance
Office of Industrial Applications and
Services

CORRESP
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ClearSign Technologies Corp.

8023 East 63rd Place, Suite 101

Tulsa, OK 74133

​

VIA EDGAR

​

November 7, 2024

​

U.S. Securities & Exchange Commission
Division of Corporation Finance

Office of Industrial Applications and Services

100 F Street, NE

Washington, D.C. 20549

​

Attn:  Kristin Lochhead

Li Xiao

​

Re: ClearSign Technologies Corp

      Amendment No. 1 to Form 10-K for the Year Ended December 31, 2023

      Filed April 1, 2024, as amended on April 26, 2024

      File No. 001-35521

​

Ladies and Gentlemen:

ClearSign Technologies Corp. (the “Company,” “we,” “our” or “us”) hereby transmits our response to the comment letter received from the staff (the “Staff,” “you” or “your”) of the U.S. Securities and Exchange Commission (the “Commission”), on October 29, 2024, regarding the Amendment No. 1 to Form 10-K for the year ended December 31, 2023, submitted to the Commission on April 26, 2024. In response to the Staff’s comment, the Company is submitting via EDGAR this response letter. For your convenience, we have repeated below your comment in bold, and have followed it with our response.

​

Amendment No. 1 to Form 10-K for the Year Ended December 31, 2023

​

Explanatory Note, page 1

​

1. We see that you amended your Form 10-K because the certifications included in the Form 10-K previously filed included typographical errors referencing incorrect dates under each Section 302 Certification, and, incorrectly identifying the Annual Report on Form 10-K, the subject of the Section 906 Certification, as being for the year ended December 31, 2022. Please refile the amendment that includes the revised certifications alongside the entire Form 10-K, including audited financial statements. Reference Question 161.08 of the Compliance and Disclosure Interpretations for Exchange Act Rules dated August 25, 2023.

​

Response:  We respectfully acknowledge the Staff’s comment and on November 7, 2024, we filed Amendment No. 2 to the Form 10-K for the year ended December 31, 2023, with the entire Form 10-K, as filed with the Commission on April 1, 2024, including audited financial statements, and revised Section 302 and 906 Certifications to correct the typographical errors referencing the incorrect dates under the Section 302 Certifications, and the incorrect identification of the Form 10-K, the subject of the Section 906 Certification, as being for the year ended December 31, 2022.

​

***

We thank you for your review of the foregoing. If you have further comments, please feel free to contact our counsel, Blake Baron, Esq., at bjb@msk.com or by telephone at (917) 546-7709.

​

​

 ​

 Sincerely,

​

 ​

 ​

​

 ​

 /s/ Colin James Deller

​

 ​

 Colin James Deller

​

 ​

 Chief Executive Officer

​

October 29, 2024
Brent Hinds
Chief Financial Officer
ClearSign Technologies Corp
8023 E. 63rd Place, Suite 101
Tulsa, Oklahoma 74133
Re:ClearSign Technologies Corp
Amendment No. 1 to Form 10-K for the Year Ended December 31, 2023
File No. 001-35521
Dear Brent Hinds:
            We have limited our review of your filing to the financial statements and related
disclosures and have the following comment.
            Please respond to this letter within ten business days by providing the requested
information or advise us as soon as possible when you will respond. If you do not believe a
comment applies to your facts and circumstances, please tell us why in your response.
            After reviewing your response to this letter, we may have additional comments.
Amendment No. 1 to Form 10-K for the Year Ended December 31, 2023
Explanatory Note, page 1
1.We see that you amended your Form 10-K because the certifications included in the
Form 10-K previously filed included typographical errors referencing incorrect dates
under each Section 302 Certification, and, incorrectly identifying the Annual Report
on Form 10-K, the subject of the Section 906 Certification, as being for the year
ended December 31, 2022.  Please refile the amendment that includes the revised
certifications alongside the entire Form 10-K, including audited financial
statements. Reference Question 161.08 of the Compliance and Disclosure
Interpretations for Exchange Act Rules dated August 25, 2023.

October 29, 2024
Page 2
            In closing, we remind you that the company and its management are responsible for
the accuracy and adequacy of their disclosures, notwithstanding any review, comments,
action or absence of action by the staff.
            Please contact Kristin Lochhead at 202-551-3664 or Li Xiao at 202-551-4391 with
any questions.
Sincerely,
Division of Corporation Finance
Office of Industrial Applications and
Services

CORRESP
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July 10, 2024

VIA EDGAR

U.S. Securities and Exchange Commission

Division of Corporation Finance

100 F Street, N.E.

Washington, D.C. 20549

 RE: ClearSign Technologies Corporation

Registration Statement on Form S-1, as amended

Filed July 3, 2024

File No. 333-279550

Acceleration Request

Requested Date: Friday, July 12, 2024

Requested Time: 4:30 p.m. Eastern Time

Ladies and Gentlemen:

In accordance with Rule 461
under the Securities Act of 1933, as amended, the undersigned registrant (the “Registrant”) hereby requests that the
Securities and Exchange Commission (the “Commission”) take appropriate action to cause the above-referenced Registration
Statement on Form S-1 (File No. 333-279550) (as amended, the “Registration Statement”) to become effective on Friday,
July 12, 2024 at 4:30 p.m. Eastern Time, or as soon thereafter as possible, or at such later time as the Registrant or its outside counsel,
Mitchell Silberberg & Knupp LLP, may orally request via telephone call to the staff.

Once the Registration Statement
has been declared effective, please orally confirm that event with our outside counsel by calling Blake Baron at (917) 546-7709.

    Very truly yours,

    ClearSign Technologies Corporation

    By:
    /s/ Colin James Deller

    Colin James Deller

    Chief Executive Officer

 ClearSign Technologies Corporation – 8023 East 63rd
Place, Suite 101, Tulsa, Oklahoma 74133 – Tel: 206.673.4848 – www.clearsign.com

United States securities and exchange commission logo
May 29, 2024
Colin Deller
Chief Executive Officer
ClearSign Technologies Corporation
8023 East 63rd Place, Suite 101
Tulsa, OK 74133
Re:ClearSign Technologies Corporation
Registration Statement on Form S-1
Filed May 20, 2024
File No. 333-279550
Dear Colin Deller:
            This is to advise you that we have not reviewed and will not review your registration
statement.
            Please refer to Rules 460 and 461 regarding requests for acceleration. We remind you
that the company and its management are responsible for the accuracy and adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action by the staff.
            Please contact Nicholas O'Leary at 202-551-4451 with any questions.
Sincerely,
Division of Corporation Finance
Office of Industrial Applications and
Services
cc:       Blake Baron, Esq.

CORRESP
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August 10, 2022

U.S. Securities and Exchange Commission

Division of Corporation Finance

100 F Street, N.E.

Washington, D.C. 20549

  RE:
  ClearSign Technologies Corporation

  Registration Statement on Form S-3

  Filed July 1, 2022

  File No. 333-265967

  Acceleration Request

  Requested Date: Friday, August 12, 2022

  Requested Time: 5:00 p.m. Eastern Time

Ladies and Gentlemen:

In accordance with Rule 461
under the Securities Act of 1933, as amended, the undersigned registrant (the “Registrant”) hereby requests
that the Securities and Exchange Commission (the “Commission”) take appropriate action to cause the above-referenced
Registration Statement on Form S-3 (File No. 333-265967) (the “Registration Statement”) to become effective
on Friday, August 12, 2022 at 5:00 p.m. Eastern Time, or as soon thereafter as possible, or at such later time as the Registrant or its
outside counsel, Mitchell Silberberg & Knupp LLP, may orally request via telephone call to the staff.

Once the Registration Statement
has been declared effective, please orally confirm that event with our outside counsel by calling Blake Baron at (917) 546-7709.

  Very truly yours,

  ClearSign Technologies Corporation

  By:
  /s/ Colin James
Deller

  Colin James
Deller

  Chief Executive Officer

ClearSign Technologies Corporation – 8023
East 63rd Place, Suite 101, Tulsa, Oklahoma 74133 – Tel: 206.673.4848 – www.clearsign.com

CORRESP
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ClearSign Technologies Corp.

8023 East 63rd Place, Suite 101

Tulsa, OK 74133

VIA EDGAR

July 19, 2022

U.S. Securities & Exchange Commission

Division of Corporation Finance

Office of Life Sciences

100 F Street, NE

Washington, D.C. 20549

  Attn:
  Tyler Howes

  Christine Westbrook

Re: ClearSign Technologies Corp.

Registration Statement on Form S-3

Filed July 1, 2022

File No. 333-265967

Ladies and Gentlemen:

ClearSign Technologies Corp.
(the “Company,” “we,” “our” or “us”) hereby transmits our
response to the comment letter received from the staff (the “Staff,” “you” or “your”)
of the U.S. Securities and Exchange Commission (the “Commission”), on July 14, 2022, regarding the Registration Statement
on Form S-3 submitted to the Commission on July 1, 2022. In response to the Staff’s comment, the Company is submitting via EDGAR
this response letter. For your convenience, we have repeated below your comment in bold, and have followed it with our response.

Registration Statement on Form S-3

Our Business

About ClearSign Technologies Corporation,
page 3

1. We note disclosure on page 3 stating your
boiler burner technology is currently undergoing commercialization in China. Please revise, where appropriate, to quantify the extent
of your operations in China. As an example only, disclose the portion of your revenues derived from China. To the extent such operations
are material to your business, please review the Division of Corporation Finance's December 20, 2021 guidance "Sample Letter to China-Based
Companies“ available at: https://www.sec.gov/corpfin/sample-letter-chinabased-companies and update your disclosure to further highlight
the legal and operational risks associated with having a material portion of your operations in China.

Response: We respectfully acknowledge the
Staff’s comment and propose the following disclosure to be added to Registration Statement, where appropriate: “We have a
satellite office located in Beijing, China to support our commercialization efforts. At this time, these operations in China are immaterial
compared to total company operations. As of March 31, 2022, our China asset balance totaled $227 thousand, or approximately 2.6% compared
to our total asset balance of $8,644 thousand.  During the year ended December 31, 2021, revenues attributable to our China operations
were $21 thousand, or approximately 3.4% compared to our total revenues of $607 thousand.”

***

We thank you for your review
of the foregoing. If you have further comments, please feel free to contact our counsel, Blake Baron, Esq., at bjb@msk.com or by telephone
at (917) 546-7709.

  Sincerely,

  /s/ Colin James Deller

  Colin James Deller

  Chief Executive Officer

United States securities and exchange commission logo
July 14, 2022
Collin James Deller
Chief Executive Officer
ClearSign Technologies Corp
8023 East 63rd Place, Suite 101
Tulsa, OK 74133
Re:ClearSign Technologies Corp
Registration Statement on Form S-3
Filed July 1, 2022
File No. 333-265967
Dear Dr. Deller:
            We have limited our review of your registration statement to those issues we have
addressed in our comment.  In our comment, we may ask you to provide us with information so
we may better understand your disclosure.
            Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe our comment applies to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
            After reviewing any amendment to your registration statement and the information you
provide in response to this comment, we may have additional comments.
Registration Statement on Form S-3
Our Business
About ClearSign Technologies Corporation, page 3
1.We note disclosure on page 3 stating your boiler burner technology is currently
undergoing commercialization in China. Please revise, where appropriate, to quantify the
extent of your operations in China. As an example only, disclose the portion of your
revenues derived from China. To the extent such operations are material to your business,
please review the Division of Corporation Finance's December 20, 2021 guidance
"Sample Letter to China-Based Companies“ available at:
https://www.sec.gov/corpfin/sample-letter-chinabased-companies and update your
disclosure to further highlight the legal and operational risks associated with having a
material portion of your operations in China.

 FirstName LastNameCollin James Deller
 Comapany NameClearSign Technologies Corp
 July 14, 2022 Page 2
 FirstName LastName
Collin James Deller
ClearSign Technologies Corp
July 14, 2022
Page 2
            We remind you that the company and its management are responsible for the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action or absence of
action by the staff.
            Refer to Rules 460 and 461 regarding requests for acceleration.  Please allow adequate
time for us to review any amendment prior to the requested effective date of the registration
statement.
            Please contact Tyler Howes at 202-551-3370 or Christine Westbrook at 202-551-5019
with any questions.
Sincerely,
Division of Corporation Finance
Office of Life Sciences
cc:       Blake Baron, Esq.

United States securities and exchange commission logo
January 5, 2022
Colin James Deller
Chief Executive Officer
ClearSign Technologies Corporation
12870 Interurban Avenue South
Seattle, WA 98168
Re:ClearSign Technologies Corp.
Form 10-K for the Fiscal Year Ended December 31, 2020
Filed March 31, 2021
File No. 001-35521
Dear Mr. Deller:
            We have completed our review of your filings.  We remind you that the company and its
management are responsible for the accuracy and adequacy of their disclosures, notwithstanding
any review, comments, action or absence of action by the staff.
Sincerely,
Division of Corporation Finance
Office of Life Sciences

CORRESP
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    Mitchell
    Silberberg & Knupp llp

    A
    Law Partnership Including Professional Corporations

    Blake
    J. Baron, Esq.

    Partner

    (917)
    546-7709 Phone

    (917) 546-7686 Fax

    bjb@msk.com

December 23, 2021

Via EDGAR

    Securities and Exchange Commission

100 F Street, N.E., Mail Stop 3233

Washington, D.C. 20549

Attn.: Tara Harkins, Kevin Kuhar

 Re: ClearSign Technologies Corp.

                                            Form 10-K for the Fiscal Year Ended December 31, 2020

                                            Filed March 31, 2021

                                            Form 10-Q for the Quarterly Period Ended September 30, 2021 Filed November 12,
                                            2021 File No. 001-35521

Dear Ms. Harkins and Mr. Kuhar:

On behalf of our client, ClearSign
Technologies Corporation (the “Company”), we set forth the below responses to the comments contained in the letter dated December 16,
2021 from the staff (the “Staff”) of the Securities and Exchange Commission regarding the Company’s quarterly reports
on Form 10-Q for the periods ended June 30, 2021 and September 30, 2021 (the “Quarterly Reports”).

For your convenience, the
Staff’s comments are repeated below in bold and are followed by the Company’s responses thereto.

Form 10-Q for the Quarterly Period Ended
September 30, 2021

Item 4. Controls and
Procedures , page 26

1. Consistent with Item
307 of Regulation S-K, please amend the filing to disclose the conclusions of your principal executive and principal financial officers
regarding the effectiveness of your disclosure controls and procedures as of the end of the period covered by the report - i.e., September 30,
2021. We note that Item 307 of Regulation S-K is a separate requirement from the requirements of Item 308 of Regulation S-K. Please note
that this comment also applies to your June 30, 2021 Form 10-Q.

In response to your comment,
the Company filed amended Form 10-Q/As for the quarterly periods ended June 30, 2021 and September 30, 2021 (collectively,
the “Amended Quarterly Reports”) to add the conclusions of the Company’s principal executive and principal financial
officers regarding the effectiveness of the Company’s disclosure controls and procedures as of the end of the respective periods.

    437 Madison Ave., 25th Floor, New York, New York 10022-7001

Phone:  (212) 509-3900  Fax:  (212) 509-7239  Website: www.msk.com

Securities and Exchange Commission

December 23, 2021

Page 2

2. We note your disclosure
that you have conducted an evaluation of the effectiveness of internal control over financial reporting as of September 30, 2021
and concluded that a material weakness exists. We note that Item 308 of Regulation S-K requires management to provide its report on internal
control over financial reporting as of only the most recent fiscal year end. Please tell us if you performed an assessment of the effectiveness
of your internal control over financial reporting as of the end of the interim period. If you did not perform an assessment of the effectiveness
of your internal control over financial reporting, please remove the references to such an evaluation in the requested amendment. To the
extent you did perform an assessment, please revise to provide the conclusions of your principal executive and principal financial officers
regarding the effectiveness of your internal control over financial reporting. Please note that this comment also applies to your June 30,
2021 Form 10-Q.

The Company respectfully acknowledges
the Staff’s comment. The Company did not perform an assessment of effectiveness of its internal control over financial reporting
as of the end of each respective interim period. In response to your comment, the Company’s Amended Quarterly Reports do not contain
the language indicating that the Company’s has performed an assessment of its internal controls for each of the respective quarterly
periods.

If we can be of any assistance
in explaining this response, please contact me at (917) 546-7709 or via e-mail (bjb@msk.com).

Sincerely,

/s/ Blake J. Baron

Blake J. Baron

Partner of

Mitchell
Silberberg & Knupp LLP

United States securities and exchange commission logo
December 16, 2021
Colin James Deller
Chief Executive Officer
ClearSign Technologies Corporation
12870 Interurban Avenue South
Seattle, WA 98168
Re:ClearSign Technologies Corp.
Form 10-K for the Fiscal Year Ended December 31, 2020
Filed March 31, 2021
Form 10-Q for the Quarterly Period Ended September 30, 2021
Filed November 12, 2021
File No. 001-35521
Dear Mr. Deller:
            We have limited our review of your filing to the financial statements and related
disclosures and have the following comments.  In some of our comments, we may ask you to
provide us with information so we may better understand your disclosure.
            Please respond to these comments within ten business days by providing the requested
information or advise us as soon as possible when you will respond.  If you do not believe our
comments apply to your facts and circumstances, please tell us why in your response.
            After reviewing your response to these comments, we may have additional comments.
Form 10-Q for the Quarterly Period Ended September 30, 2021
Item 4. Controls and Procedures , page 26
1.Consistent with Item 307 of Regulation S-K, please amend the filing to disclose
the conclusions of your principal executive and principal financial officers regarding
the effectiveness of your disclosure controls and procedures as of the end of the
period covered by the report - i.e., September 30, 2021. We note that Item 307 of
Regulation S-K is a separate requirement from the requirements of Item 308 of Regulation
S-K. Please note that this comment also applies to your June 30, 2021 Form 10-Q.
2.We note your disclosure that you have conducted an evaluation of the effectiveness
of internal control over financial reporting as of September 30, 2021 and concluded that a
material weakness exists. We note that Item 308 of Regulation S-K requires management

 FirstName LastNameColin James  Deller
 Comapany NameClearSign Technologies Corporation
 December 16, 2021 Page 2
 FirstName LastName
Colin James  Deller
ClearSign Technologies Corporation
December 16, 2021
Page 2
to provide its report on internal control over financial reporting as of only the most recent
fiscal year end.  Please tell us if you performed an assessment of the effectiveness of your
internal control over financial reporting as of the end of the interim period. If you did not
perform an assessment of the effectiveness of your internal control over financial
reporting, please remove the references to such an evaluation in the requested amendment.
To the extent you did perform an assessment, please revise to provide the conclusions of
your principal executive and principal financial officers regarding the effectiveness of
your internal control over financial reporting. Please note that this comment also applies
to your June 30, 2021 Form 10-Q.
            In closing, we remind you that the company and its management are responsible for the
accuracy and adequacy of their disclosures, notwithstanding any review, comments, action or
absence of action by the staff.
            You may contact Tara Harkins (202) 551-3639 or Kevin Kuhar, Accounting Branch
Chief, at (202) 551-3662 with any questions.
Sincerely,
Division of Corporation Finance
Office of Life Sciences

July 10, 2019
Colin James Deller
Chief Executive Officer
ClearSign Combustion Corporation
12870 Interurban Avenue South
Seattle, Washington 98168
Re:ClearSign Combustion Corporation
Registration Statement on Form S-3
Filed June 27, 2019
File No. 333-232402
Dear Mr. Deller:
            This is to advise you that we have not reviewed and will not review your registration
statement.
            Please refer to Rules 460 and 461 regarding requests for acceleration.  We remind you
that the company and its management are responsible for the accuracy and adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action by the staff.
            Please contact Eric Atallah at (202) 551-3663 with any questions.
Sincerely,
Division of Corporation Finance
Office of Electronics and Machinery

CORRESP
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July 10, 2019

United States Securities and Exchange Commission

Division of Corporation Finance

100 F Street, N.E.

Washington, D.C. 20549

Attention: Eric Atallah

 Re: Request for Acceleration

ClearSign
Combustion Corporation - Registration Statement on Form S-3

(SEC
File No. 333-232402)

Mr. Atallah:

Pursuant to Rule 461 of the Securities Act
of 1933, as amended, ClearSign Combustion Corporation (the “Company”) respectfully requests that its Registration Statement
on Form S-3 (SEC File No. 333-232402) be ordered effective at 5:00 p.m., Washington, D.C. time, on July 12, 2019, or as soon thereafter
as practicable. The Company requests that it be notified of such effectiveness by a telephone call to Mary Ann Sapone at (310)
312-3258.

    Sincerely,

    CLEARSIGN COMBUSTION CORPORATION

    By:
    /s/ Colin
James Deller

    Colin
James Deller, Chief Executive Officer

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

       DIVISION OF
CORPORATION FINANCE

 November 19, 2018

By E-Mail

Andrew D. Hudders, Esq.
Golenbock Eiseman Assor Bell & Peskoe  LLP
711 Third Avenue – 17th Floor
New York, NY 10022

Re: ClearSign Combustion Corporation
Preliminary Proxy Statement  filed Anthony DiGiandomenico
Filed on November 9, 2018
File No. 001-35521

Dear M r. Hudders :

We have reviewed your filing and have the following comments. In some of our comments,
we may ask you to provide us with information so  we may bett er understand your disclosure.

Please respond to this letter by amending your filing, by providing the requested
information, or by advising us when you will provide the requested response. If you do not
believe our comments apply to your fact s and circumstances or do not believe an amendment is
appropriate, please tell us why in your response.

After reviewing any amendment to your filing and the information you provide in
response to th ese comments , we may have additional comments.

Prelimina ry Proxy Statement
1. Please provide us your a nalysis of whether MDB Capital G roup LLC and Richard
Deutsch are participants in your solicitation. See Instruction 3 to Item 4  of Schedule 14A
for guidance.
2. Each statement or assertion of opinion or belief must b e clearly characterized as such,
and a reasonable factual basis must exist for each such opinion or belief. Support for
opinions or beliefs should be self -evident, disclosed in the proxy statement or provided to
the staff on a supplemental basis. Provide s upport for your statement that “…the
company has been underperforming and is not taking advantage of its resources and
opportunities under the current Board and management.”
3. Please clarify  on page 2 the meaning of “ineffective pursuit of business opportunities.”

Andrew D. Hudders, Esq.
Golenbock Eiseman Assor Bell & Peskoe LLP
November 19 , 2018
Page 2

 4. Revise your disclosure to generally address whether the replacement of all or a majority
of the current directors would have a negative effect on the company. For example,
describe  whether any members of management would be entitled to receive
compensation under any change of control agreement or similar provision in an
employment agreement and whether any company obligation would be accelerated.++
5. With respect to the first full paragraph on page 3, please revise your disclosure to explain
whether you are entitled to revise the proposals for an eventual special meeting under
Washington law.  We may have further comment.
6. Refer to the fifth full paragraph on page 3. With a view towar ds revised disclosure, tell us
how you are “sure that the Company will try to say that [you] will not have the full
percentage of votes to call a meeting if [you deliver] less than 25% but more than 10%.”
You must avoid issuing statements that directly or indirectly impugn the character,
integrity or personal reputation or make charges of illegal, improper or immoral conduct
without factual foundation. In this regard, note that the factual foundation for such
assertion must be reasonable. Refer to Rule 14a -9.
7. Please tell us the Washington state law that provides for consents to be delivered within
seventy (70) days  of the record date.

Past Contacts, page 5
8. Please provide us supplemental support regarding Mr. Tokman’s business
accomplishments (first full par agraph of page 6 ) and regarding  the email Mr. Bell sent to
Mr. DiGiandomenico on October 4, 2018 (second full paragraph of page 6) .

Written Request Procedures, page 8
9. Please tell us the authority upon which you based your disclosure that the proxies may
use their proxy authority to apply for a court order tha t the special meeting be held.

Certain Information Regarding the Solicitation Participant, page 10
10. We note your disclosure in the last paragraph on page 10. With a view toward revised
disclosure, please tell us whether the company paid compensation in excess of $120,000
to MDB Capital Group, since the beginning of the registrant’ s last fiscal year , and
whether MDB Capital Group is an associate of Mr. DiGiandomenico .

Schedule II, page 14
11. Please update this disclosure .

Andrew D. Hudders, Esq.
Golenbock Eiseman Assor Bell & Peskoe LLP
November 19 , 2018
Page 3

 Form of Proxy Card
12. Given that the solicitation relates solely to the calling of a special meeting, tell us why
you have included the five  proposals you may present at an eventual special meeting in
the proxy card .

We remind you that the filing persons are responsible for the accuracy and adequacy of
their disclosures, notwithstanding any review, comments, action or absence of action by the  staff

Please direct any questions to me at (202) 551 -3619.

        Sincerely,

        /s/ Daniel F. Duchovny
        Daniel F. Duchovny
        Special Counsel
        Office of Mergers and Acquisitions

September 19, 2018
Stephen E. Pirnat
Chief Executive Officer
ClearSign Combustion Corporation
12870 Interuban Avenue South
Seattle, Washington 98168
Re:ClearSign Combustion Corporation
Registration Statement on Form S-3
Filed August 31, 2018
File No. 333-227169
Dear Mr. Pirnat:
            This is to advise you that we have not reviewed and will not review your registration
statement.
            Please refer to Rules 460 and 461 regarding requests for acceleration.  We remind you
that the company and its management are responsible for the accuracy and adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action by the staff.
            Please contact Thomas Jones at 202-551-3602 with any questions.
Sincerely,
Division of Corporation Finance
Office of Electronics and Machinery
cc:       Melanie Figueroa, Esq.

CORRESP
1
filename1.htm

September 19, 2018

United States Securities and Exchange Commission

Division of Corporation Finance

100 F Street, N.E.

Washington, D.C. 20549

Attention: Thomas Jones

 Re: Request for Acceleration

ClearSign Combustion Corporation - Registration Statement on Form S-3

(SEC
File No. 333-227169)

Mr. Jones:

Pursuant to Rule 461 of the Securities Act
of 1933, as amended, ClearSign Combustion Corporation (the “Company”) respectfully requests that its Registration Statement
on Form S-3 (SEC File No. 333-227169) be ordered effective at 5:00 p.m., Washington, D.C. time, on September 21, 2018, or as soon
thereafter as practicable. The Company requests that it be notified of such effectiveness by a telephone call to Melanie Figueroa
at (917) 546-7707, or in her absence, Mary Ann Sapone at (310) 312-3258.

    Sincerely,

    CLEARSIGN COMBUSTION CORPORATION

    By:
    /s/ Stephen E. Pirnat

    Stephen E. Pirnat, Chief Executive Officer

CORRESP
1
filename1.htm

CLEARSIGN COMBUSTION CORPORATION

12870 Interurban Avenue South

Seattle, WA 98168

January 5, 2016

VIA EDGAR

Ms. Amanda Ravitz

Assistant Director

United States Securities and Exchange Commission

Division of Corporation Finance

100 F Street NE

Washington, D.C. 20549

    Re:
    ClearSign Combustion Corporation

    Form S-3 filed on December 29, 2015

    File No. 333-208784

Dear Ms. Ravitz:

ClearSign Combustion
Corporation (the “Company”) hereby requests that the Securities and Exchange Commission (the “Commission”)
take appropriate action to make the above-captioned registration statement be ordered effective at 4:00 p.m., Eastern time, on
January 7, 2016 or as soon as practicable thereafter.

In requesting acceleration,
the Company acknowledges that:

(1)	should the Commission
or the staff, acting pursuant to delegated authority, declare the filing effective, it does not foreclose the Commission from taking
any action with respect to the filing;

(2)	the action of
the Commission or the staff, acting pursuant to delegated authority in declaring the filing effective, does not relieve the Company
from its full responsibility for the adequacy and accuracy of the disclosure in the filing; and

(3)	the Company
may not assert staff comments and the declaration of effectiveness as a defense in any proceeding initiated by the Commission or
any person under the federal securities laws of the United States.

    Very truly yours,

    CLEARSIGN COMBUSTION CORPORATION

    By:
    /s/ James N. Harmon

    James N. Harmon, Chief Financial Officer

cc (via e-mail): Kevin Friedmann, Esq.

Mail Stop 3030
January 4, 2016

Stephen E. Pirnat
Chief Executive Officer
ClearSign Combustion Corporation
12870 Interurban Avenue South
Seattle, Washington 98168

Re: ClearSign  Combustion Corporation
  Registration Statement on Form S-3
Filed  December 29, 2015
  File No.  333-208784

Dear Mr. Pirnat :

This is to advise you that we have not reviewed and will not review your registration
statement .

We urge all persons who are responsible for the accuracy and adequacy of the disclosure
in the filing to be certain that the filing includes the information the Securities Act of 193 3 and
all applicable Securities  Act rules require.   Since the company and its management are  in
possession of all facts relating to a company’s disclosure, they are responsible for the accuracy
and adequacy of the disclosures they have made.

In the event you request acceleration of t he effective date of the pending regist ration
statement, please provide  a written statement from the company acknowledging that:

 should the Commission or the staff, acting pursuant to delegated authority, declare the
filing effective, it does not foreclos e the Commission from taking any action with respect
to the filing;

 the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the ad equacy and accuracy of the disclosure in the filing; and

 the company may not assert staff comments and the declaration of effectiveness as a
defense in any proceeding initiated by the Commission or any person under the federal
securities laws of the Unit ed States.

Please refer to Rules 460 and 461 regarding requests for  acceleration .  We will consider a
written request for acceleration of the effective date of the registration statement as confirmation
of the fact that those requesting acceleration are a ware of their respective responsibilities under

Stephen E. Pirnat
ClearSign Combustion Corporation
January 4, 2016
Page 2

 the Securities Act of 1933 and the Securities Exchange Act of 1934 as they relate to the proposed
public offering of the registered securities .

You may contact Geoff Kruczek  at (202) 551 -3641  with any ques tions.

Sincerely,

 /s/ Geoff Kruczek for

Amanda Ravitz
        Assistant Director
        Office of Electronics and Machinery

cc: Kevin Friedmann , Esq.

CORRESP
1
filename1.htm

MDB Capital Group, LLC

401 Wilshire Boulevard, Suite 1020

Santa Monica, CA 90401

April 20, 2012

Securities and Exchange Commission

100 F. Street, N.E.

Washington, D.C. 20549

Attn: Mary Beth Breslin

 Re: ClearSign Combustion Corporation

Registration Statement on Form S-1

File No. 333-177946

Ladies and Gentlemen:

In accordance with the provisions of Rule 460 under the Securities
Act of 1933, MDB Capital Group, LLC, as underwriter of the proposed offering of 3,000,000 shares of Common Stock of ClearSign Combustion
Corporation, distributed copies of the Preliminary Prospectus dated April 17, 2012 as follows:

 (1) 557 copies to institutions;

 (2) 25 copies to FINRA members; and

 (3) 1,169 copies to individual investors.

We have been informed by participating dealers that, in accordance
with Rule 15c2-8 under the Securities Exchange Act of 1934, copies of the Preliminary Prospectus dated April 17, 2012 are being
distributed to all persons to whom it is expected confirmations of a sale will be sent; and we likewise so distributed copies to
all customers of ours.

We have adequate capital to underwrite a
“firm commitment.”

    Very truly yours,

    MDB Capital Group, LLC

    By: /s/ Gary Schuman

           Gary Schuman

           CFO & CCO

MDB Capital Group, LLC

401 Wilshire Boulevard, Suite 1020

Santa Monica, CA 90401

April 20, 2012

Securities and Exchange Commission

100 F. Street, N.E.

Washington, D.C. 20549

Attn: Mary Beth Breslin

 Re: ClearSign Combustion Corporation

Registration Statement on Form S-1

File No. 333-177946

Ladies and Gentlemen:

In connection with the Registration Statement on Form S-1 of
ClearSign Combustion Corporation (the “Company”), the undersigned hereby joins the request of the Company that the
effectiveness of said Registration Statement be accelerated to 4:00 p.m. Eastern time on April 24, 2012, or as soon thereafter
as practicable.

    Very truly yours,

    MDB Capital Group, LLC

    By: /s/ Gary Schuman

           Gary Schuman

           CFO & CCO

CORRESP
1
filename1.htm

CLEARSIGN COMBUSTION CORPORATION

12870 Interurban Avenue South

Seattle, Washington 98168

April 20, 2012

VIA EDGAR

Amanda Ravitz

Assistant Director

United States Securities and Exchange Commission

Division of Corporate Finance/Mail Stop 4561

100 F Street, N.E.

Washington, D.C. 20549

 Re: ClearSign Combustion Corporation

Registration Statement on Form S-1

Filed on November 14, 2011 and amended on December
28, 2011,

February 7, 2012, March 9, 2012, April 6, 2012 and
April 18, 2012

File No. 333-177946

Dear Ms. Ravitz:

ClearSign Combustion Corporation (the “Company”)
hereby requests that the Securities and Exchange Commission take appropriate action to make the above-captioned registration statement
be ordered effective at 4 p.m., Eastern time, on April 24, 2012 or as soon as practicable thereafter.

In requesting acceleration, the Company
acknowledges that:

(1)	should the Commission or the staff,
acting pursuant to delegated authority, declare the filing effective, it does not foreclose the Commission from taking any action
with respect to the filing;

(2)	the action of the Commission or the
staff, acting pursuant to delegated authority in declaring the filing effective does not relieve the Company from its full responsibility
for the adequacy and accuracy of the disclosure in the filing; and

(3)	the Company may not assert the declaration
of effectiveness as a defense in any proceeding initiated by the Commission or any person under the federal securities laws of
the United States.

    Very truly yours,

    CLEARSIGN COMBUSTION CORPORATION

    By:
    /s/ Richard Rutkowski

    Richard Rutkowski, Chief Executive Officer

February 17, 2012
 Via E-mail

Richard Rutkowski Chief Executive Officer ClearSign Combustion Corporation 12870 Interurban Avenue South Seattle, Washington 98168
Re: ClearSign Combustion Corporation
 Amendment No. 2 to Registra tion Statement on Form S-1
Filed February 7, 2012
  File No. 333-177946

Dear Mr. Rutkowski:

We have reviewed your registration statem ent and have the following comments.  In
some of our comments, we may ask you to provi de us with information so we may better
understand your disclosure.
 Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe  our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
 After reviewing any amendment to your re gistration statement and the information you
provide in response to these comments , we may have additional comments.
 Prospectus Cover Page

 1. We note your response to prior comment 1 that once the price or price range is
determined you will file a prospectus supplemen t that provides this information and that
you do not have any price ranges included at th is time.  Please note that paragraph 16 of
Schedule A of the Securities Act and Regula tion S-K Item 501(b)(3) require that you
disclose the price at which the securities wi ll be sold.  Please revi se the underwritten
offering prospectus to include a price range  and all non-Rule 430A information prior to
circulating any preliminary prospectus.  With respect to the selling shareholder
prospectus, given the lack of an established market for your securitie s, please note that a
statement that selling shareholders will sell “a t market prices” is insufficient to satisfy
your disclosure obligation.  Th erefore, please disclose th e fixed price at which the
securities will be sold.  We will not object if you also elect to disclose that the selling
shareholders will sell at the fixed price until  your shares are quoted on the OTC Bulletin
Board and thereafter at prevailing market prices or privately negotiated prices.

Richard Rutkowski ClearSign Combustion Corporation February 17, 2012 Page 2

Research and Development Plan, page 25

 2. We note you revised the disclosure on page 25 in response to prior comment 5.  Please
revise to clarify the costs associated with completing each step in the development plan
rather than only the portion of the offering proceeds that will be applied to each step.

We urge all persons who are responsible for th e accuracy and adequacy of the disclosure
in the filing to be certain that the filing incl udes the information the Securities Act of 1933 and
all applicable Securities Act rules require.  Since the company and its management are in
possession of all facts relating to a company’s disc losure, they are responsible for the accuracy
and adequacy of the disclosures they have made.
Notwithstanding our comments, in the event you request acceleration of  the effective date
of the pending registration statement please pr ovide a written statement from the company
acknowledging that:
 should the Commission or the staff, acting purs uant to delegated authority, declare the
filing effective, it does not foreclose the Co mmission from taking any action with respect
to the filing;

 the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the adequacy and accuracy of the disclosure in the filing; and

 the company may not assert staff comments a nd the declaration of effectiveness as a
defense in any proceeding initiated by the Commission or any person under the federal
securities laws of the United States.

Please refer to Rules 460 and 461 regarding re quests for acceleration.  We will consider a
written request for acceleration of  the effective date of the regi stration statement as confirmation
of the fact that those reques ting acceleration are aware of thei r respective responsibilities under
the Securities Act of 1933 and the Securities Excha nge Act of 1934 as they relate to the proposed
public offering of the securities specified in th e above registration stat ement.  Please allow
adequate time for us to review any amendment prior to the requested effective date of the
registration statement.

Richard Rutkowski ClearSign Combustion Corporation February 17, 2012 Page 3

 You may contact Praveen Kart holy at 202-551-3778 or Brian Cascio, Accounting Branch
Chief, at 202-551-3676 if you have questions rega rding comments on the financial statements
and related matters.  Please contact Jay Mumf ord at 202-551-3637 or Mary Beth Breslin at 202-
551-3625 with any other questions.

Sincerely,

/s/ Mary Beth Breslin for

        A m a n d a  R a v i t z          A s s i s t a n t  D i r e c t o r   cc (via e-mail): Kevin Friedmann

January 13, 2012
 Via E-mail

Richard Rutkowski Chief Executive Officer ClearSign Combustion Corporation 12870 Interurban Avenue South Seattle, Washington 98168
Re: ClearSign Combustion Corporation
 Amendment No. 1 to Registra tion Statement on Form S-1
Filed December 28, 2011
  File No. 333-177946

Dear Mr. Rutkowski:

We have reviewed your registration statem ent and have the following comments.  In
some of our comments, we may ask you to provi de us with information so we may better
understand your disclosure.
 Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe  our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
 After reviewing any amendment to your re gistration statement and the information you
provide in response to these comments , we may have additional comments.
 Prospectus Cover Page

1. We note your revised disclosure in response to  prior comment 2 that “although a specific
price cannot be determined at this time,” you have “estimated an initial price” of $4.00
per share.  From the disclosure, it remains unclear whether the offering price has been
fixed.  Please revise to clarify, if true, th at the offering price has been fixed at $4.00.
 The Industry, page 1

 2. We note your response to prior comment 9; how ever, it is unclear from the materials
provided in response to the comment how you estim ated the value of the capital assets in
the United States relating to combus tion of hydrocarbon and other fuels.

Richard Rutkowski ClearSign Combustion Corporation January 13, 2012 Page 2

 The Offering, page 6

 3. We note your response to prior comment 15.  He re and in the “Use of Proceeds” section
beginning on page 65, please revise to qua ntify the approximate amount of proceeds
intended to be used for each purpose.
 System Results, page 22

 4. We note your response to prior comment 16 and your revised disclosu re on pages 22 - 25.
Please revise to disclose how many experi ments were conducted and how often the
observed results occurred.  Also, please demonstrate to us that your testing produced
statistically significant results.
Research and Development Plan, page 25

 5. We note your response to prior comment 18; however, you have not disclosed the costs
associated with completing each bullet point.  Please revise accordingly.
 Competitive Advantage, page 38

6. We note your response to prior comment 21; however, we continue to note a number of
statements in this section that definitively  describe your product as producing a certain
result compared to existing t echnology.  It is unclear why yo u believe it is appropriate to
retain such statements based on your current stage of development. As such, we reissue
prior comment 21.
 Underwriting Discounts and Expenses, page 62

 7. Please expand your disclosure to describe in more detail the agreement to pay the
underwriters a non-accountable expense al lowance equal to $160,000, including what
expenses are covered in this agreement.  Also, please tell us where you have filed this
agreement as an exhibit.
 Financial Statements, page F-1

 Note 8 - Subsequent Events, page F-21

 8. We note your disclosure that “all share and pe r price information has been retroactively
adjusted to reflect the stock split” that  was effective December 22, 2011.  Please tell us
how the financial statements in this filing ha ve been retroactively adjusted for the stock
split. Refer to the guidance in SAB T opic 4.C and FASB ASC 260-10-55-12.

Richard Rutkowski ClearSign Combustion Corporation January 13, 2012 Page 3

 Exhibit 5.1

 9. Please tell us why the opinion as to the sel ling stockholder shares is qualified to the
declaration of effectiveness of the registration statement.

We urge all persons who are responsible for th e accuracy and adequacy of the disclosure
in the filing to be certain that the filing incl udes the information the Securities Act of 1933 and
all applicable Securities Act rules require.  Since the company and its management are in
possession of all facts relating to a company’s disc losure, they are responsible for the accuracy
and adequacy of the disclosures they have made.
Notwithstanding our comments, in the event you request acceleration of  the effective date
of the pending registration statement please pr ovide a written statement from the company
acknowledging that:
 should the Commission or the staff, acting purs uant to delegated authority, declare the
filing effective, it does not foreclose the Co mmission from taking any action with respect
to the filing;

 the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the adequacy and accuracy of the disclosure in the filing; and

 the company may not assert staff comments a nd the declaration of effectiveness as a
defense in any proceeding initiated by the Commission or any person under the federal
securities laws of the United States.

Please refer to Rules 460 and 461 regarding re quests for acceleration.  We will consider a
written request for acceleration of  the effective date of the regi stration statement as confirmation
of the fact that those reques ting acceleration are aware of thei r respective responsibilities under
the Securities Act of 1933 and the Securities Excha nge Act of 1934 as they relate to the proposed
public offering of the securities specified in th e above registration stat ement.  Please allow
adequate time for us to review any amendment prior to the requested effective date of the
registration statement.

Richard Rutkowski ClearSign Combustion Corporation January 13, 2012 Page 4

 You may contact Praveen Kart holy at 202-551-3778 or Brian Cascio, Accounting Branch
Chief, at 202-551-3676 if you have questions rega rding comments on the financial statements
and related matters.  Please contact Jay Mumf ord at 202-551-3637 or Mary Beth Breslin, Senior
Attorney, at 202-551-3625 w ith any other questions.

Sincerely,

 /s/ Russell Mancuso
        R u s s e l l  M a n c u s o          B r a n c h  C h i e f    cc (via e-mail): Kevin Friedmann, Esq.

December 9, 2011
 Via E-mail

Richard Rutkowski Chief Executive Officer ClearSign Combustion Corporation 12870 Interurban Avenue South Seattle, Washington 98168
Re: ClearSign Combustion Corporation
 Registration Statement on Form S-1
Filed November 14, 2011
  File No. 333-177946

Dear Mr. Rutkowski:

We have reviewed your registration statem ent and have the following comments.  In
some of our comments, we may ask you to provi de us with information so we may better
understand your disclosure.
 Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe  our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
 After reviewing any amendment to your re gistration statement and the information you
provide in response to these comments , we may have additional comments.
 Public Offering Prospectus Cover Page

 1. We note your cover page includes the “subj ect to completion” legend but does not
indicate that a price range will be included in the event a preliminary prospectus is
circulated.  Please confirm that any prelimin ary prospectus you circulate will include all
non-Rule 430A information.  This includes th e price range and related information based
on a bona fide  estimate of the public offering pr ice within that range, and other
information that was left blank throughout th e document.  Also note that we may have
additional comments after you file this information.
2. Here and elsewhere in your document, as appr opriate, please includ e a brief description
of the concurrent selling stoc kholder offering.  Also disclose how the price of the shares
being offered by the selling stockholders diffe rs from the price of the shares you are
offering in this underwritten offering.

Richard Rutkowski ClearSign Combustion Corporation December 9, 2011 Page 2

3. Please revise the cover page to disclose your relationship with MDB Capital Group and
its affiliates.  Please also revise to disclose on the c over page the dollar amount and
percentage of the net proceeds of the offering th at will be paid to or for the benefit of the
underwriters and/or their affiliates.
Graphics, page i and back cover

4. We note the significant amount of text in your graphics and that much of that text is already
contained elsewhere in your prospectus.  You may use text on the inside cover page only to
the extent necessary to explain briefly the visuals in the presentation.  Please revise
accordingly.

5. The use of the photographs in your graphics is  not appropriate for your level of product
development.  While we note that you do not have revenues at this time, readers may be
left with the impression that products you are selling or trying  to sell are being shown in
the photographs.  Please revise accordingly.
Special Note Regarding Forwar d Looking Statements, page iii

 6. Please move this section to a later section of your prospectus  rather than prior to the
summary and the risk factors.
About ClearSign Combusti on Corporation, page 1

 7. We note your brief summary.  The summary s hould be a balanced presentation of your
business that presents the ke y aspects of the offering and your business.  Please expand
your disclosure here and elsewhere as a ppropriate to explain the status of your
technology and that you have not yet de veloped products based on your technology.
Also highlight that your financ ial statements have been pr epared on the basis that you
will continue as a going concern and that there is substantial doubt about your ability to
continue as a going concern.  Please quantify your net losses in  the past two fiscal years
and any interim periods, and indicate the amount of your accumulated deficit.

8. We note your statements in the first para graph that you “design, develop and market”
technologies.   As you have not yet introdu ced a product, please remove “market” from
this list.
 Our Industry, page 1

 9. We note the statements in this paragraph about  the “trillions” in cap ital assets and that
operators invest “billions” in  installing, maintaining and upgr ading these systems.  We
further note your disclosure in the “Our Target  Markets” section on pa ge 3.  It is unclear
why you have implied that these markets are yo ur addressable markets, as it appears your
potential products would only be applicable to a subset of these markets.  Please revise or

Richard Rutkowski ClearSign Combustion Corporation December 9, 2011 Page 3

 advise.  Also, please provide us independent  objective support for the statement on page
1 regarding world total energy consumption and on page 3 regarding the size of your
addressable market.
Our Proprietary Technology, page 2

 10. We note your statement that you believe your  platform “may increase energy, and
improve fuel flexibility and environmental pe rformance for most types of industrial and
commercial combustion systems.”  Please revise  your disclosure to clearly identify the
specific basis for your belief, and clarify the products or  technology against which you
are comparing your platform. If you have not  yet developed a product that has been
objectively tested with statistic ally significant results, it is unclear why you believe it is
appropriate to make these claims in your document.
Intellectual Property, page 3

 11. Please revise your disclosure so that i nvestors can understand the nature of your
intellectual property.  In this regard, please clarify the terms “prior art” and “reduction to
practice” by using concrete, every day terms.  Also, your disclosure here should be
balanced in describing the limitations of your current intellect ual property and its
protections.  Please revise accordingly.

Prototypes and Experime ntal Data, page 3

 12. We note your vague disclosure about having “designed and/or built several prototype
systems” and that you have conducted “numer ous” and “repeated” experiments.  Please
expand and revise your disclo sure to provide more spec ific disclosure about your
prototypes and experimental data.  Also avoid marketing jargon such as “will be a rapid path to commercialization and a robust product pipeline.”

Partners, page 4

 13. Please disclose the extent of your current agr eements with potential partners. If you have
not commenced seeking out such partners, please clearly state that fact here.

The Offering, page 5

 14. Tell us where you have provided disclosure pu rsuant to Item 505(a) of Regulation S-K.

15. We note you state the proceeds are to be used  for “working capital and general corporate
purposes,” yet on page 36 you state that th e “proceeds received from this offering are
expected to be used in our efforts related to  research and developm ent, protection of our
intellectual property, and expl oration of market opportunities.”   Please reconcile and
revise as necessary to state clearly  the intended uses of proceeds.

Richard Rutkowski ClearSign Combustion Corporation December 9, 2011 Page 4

 System Results, page 21

 16. Please expand your disclosure to identify the basis for the results in the photographs
provided in your prospectus.  For example, if these photographs were taken during the
course of your experiments, please disclo se how many experiments were run and how
often the observed results occurred.
17. We note your disclosure in the first paragra ph on page 24.  It is unclear why you believe
it is appropriate to include the disclosure in  the first paragraph on page 24 regarding the
“favorable” response of “subject matter expert s” and “positive resu lts” of potential
customers to your “selective pr esentations” of the data obt ained from the experiments
you conducted without providing significant addi tional disclosure a bout the nature and
scope of the experiments conducted, the pres entations given, how you found the subject
matter experts and the criteria you used to id entify them as such, and other important
contextual information.  Pl ease advise or revise.
  Research and Development Plan, page 24

 18. We note your discussion of wher e your R&D efforts are to be  focused in the future.
Please expand your disclosure to describe in details the steps required to complete the
sequence described in the four  bullet points and the anticipa ted costs associated with
completing each bullet point.

Product Roadmap and Path to Commercialization, page 25

 19. We note you describe your technology in mark eting terms, such as your statements that
your technology “easily and cost-effectively”  combines with pollution control and
promises “to improve the reliability of existing systems while lowering operating costs and energy use.”  Please revise to av oid the use of marketing terms.

Competition and Barriers to Entry, page 36

 20. We note you have only described the shortc omings of your competitors’ offerings.
Please expand to describe the benefits your competitors’ products compared to your
technology.   Also, please expand your disclosure  to disclose that your competitors have
greater financial resources and market share than you do.

Competitive Advantage, page 36

 21. Please provide independent, objective suppor t for your statements in this section
regarding the advantages of your technology.  For example, we note your statements that
your technology has the potential  to deliver “discernable a nd measurable advantages as
compared to currently available technology.”  We also note your stat ements in the bullet
points on page 37.

Richard Rutkowski ClearSign Combustion Corporation December 9, 2011 Page 5

 Management’s Discussion and Analysis of Financ ial Condition and Results of Operations, page
40
 Liquidity and Capital Resources, page 42

 22. We note that you are a development stage company and there is substantial doubt
regarding your ability to continue as a going concern. Please expand to describe your
plan of operations, including the expected  timeframe and funding requirements to
develop your technology and products a nd the expected source of your funding
requirements. Please also disclose the dollar amount of financing you believe is required
to continue your business over the next twelve  months.  For further guidance, refer to
Section IV.A. of Securities Act Releas e 33-8350 “Commission Guidance Regarding
Management's Discussion and Analysis of Financial Conditio n and Results of
Operations.”
Technical Advisors, page 48

 23. Please expand your description of the role of the technical advisors for whom you
provide biographical information here.  Also  expand your discussion of the compensation
of these advisors, including cash, stock, and/or  options issued to date, and clarify how
compensation is determined.  Indicate whet her you have any agreements with these
advisors, including compensation agreements.
 Current and Future Compensation Practices, page 51

 24. While you state that currentl y, your compensation program is only for cash, we note you
state that during 2011 you “implemented a co mpensation program” of base salary and
stock.  Please expand your disclosure to de scribe this program in  detail, including the
compensation to be paid and how that compensation was determined.
25. We note you state in setting compensation, you look at salaries paid to others in business
similar to yours.  Please identify those busin esses and tell how the compensation you paid
compares to the other bu sinesses’ compensation.
 26. We note you state that you may pay bonuses in the future for achievement of agreed upon
targets.  Please tell us whether those target s have been set and, if so, why you have not
disclosed them.
 Capitalization, page 64

 27. Please remove cash and cash equivalents from  the Capitalization ta ble on page 64 since
this is not a component of capitalization.

Richard Rutkowski ClearSign Combustion Corporation December 9, 2011 Page 6

 Unaudited Financial Statements for the Quarter Ended June 30, 2011

 28. Please update the financial statements as required by Article 8-08 of Regulation S-X.

Note 4. Stockholder’s Equity/(Deficit), page F-17

 29. We note that you issued 109,091 and 101,818 shares of common stock as part of issuance
costs.  Please clarify where this is reflected  in the Statement of Changes in Stockholder’s
Equity/(Deficit).
Selling Security Holder Prospectus Cover, page II-2

 30. Note that Schedule A, paragraph 16 of th e Securities Act and Item 501(b)(3) of
Regulation S-K require that you disclose the pr ice at which the securities will be sold.
Given the lack of an established market for your securities, a statement that selling
stockholders will sell “at prevailing market prices” is insufficient to satisfy your
disclosure obligation.  Please disclose the fixe d price you intend to sell  the shares listed in
this prospectus.  We will not obj ect if you disclose that the se curities will be sold at the
disclosed fixed price until your shares ar e listed on the NASDAQ and thereafter at
prevailing market prices or pr ivately negotiated prices.

Selling Security Holder Table, page II-6

 31. Please tell us whether any of the selling shar eholders are broker-dealers or affiliates of
broker-dealers. A selling stockholder who is an affiliate of a broker-dealer must be
identified in the prospectus as an underwriter unless the prospectus stat es, if true, that: the
selling shareholder purchased the shares being registered for re sale in the ordinary course
of business, and at the time of the purchase, the selling shareholder had no agreements or
understandings, directly or indi rectly, with any person to dist ribute the securities. Please
revise as appropriate.
Exhibits

 32. Please file all exhibits with your next amen dment.  We may have further comment after
reviewing those exhibits.
 33. To the extent there is a delay in requesting e ffectiveness of your registration statement, or
there is any change, other than typographical, made to the financial statements, or there
have been intervening events  since the prior filing that are material to the company,
please provide a currently dated and signed consent from your independent accountants
with the next amendment.

We urge all persons who are responsible for th e accuracy and adequacy of the disclosure
in the filing to be certain that the filing incl udes the information the Securities Act of 1933 and

Richard Rutkowski ClearSign Combustion Corporation December 9, 2011 Page 7

 all applicable Securities Act rules require.  Since the company and its management are in
possession of all facts relating to a company’s disc losure, they are responsible for the accuracy
and adequacy of the disclosures they have made.
Notwithstanding our comments, in the event you request acceleration of  the effective date
of the pending registration statement please pr ovide a written statement from the company
acknowledging that:
 should the Commission or the staff, acting purs uant to delegated authority, declare the
filing effective, it does not foreclose the Co mmission from taking any action with respect
to the filing;

 the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the adequacy and accuracy of the disclosure in the filing; and

 the company may not assert staff comments a nd the declaration of effectiveness as a
defense in any proceeding initiated by the Commission or any person under the federal securities laws of the United States.

Please refer to Rules 460 and 461 regarding re quests for acceleration.  We will consider a
written request for acceleration of  the effective date of the regi stration statement as confirmation
of the fact that those reques ting acceleration are aware of thei r respective responsibilities under
the Securities Act of 1933 and the Securities Excha nge Act of 1934 as they relate to the proposed