<SEC-DOCUMENT>0001104659-21-088913.txt : 20210702
<SEC-HEADER>0001104659-21-088913.hdr.sgml : 20210702
<ACCEPTANCE-DATETIME>20210702163144
ACCESSION NUMBER:		0001104659-21-088913
CONFORMED SUBMISSION TYPE:	S-8 POS
PUBLIC DOCUMENT COUNT:		5
FILED AS OF DATE:		20210702
DATE AS OF CHANGE:		20210702
EFFECTIVENESS DATE:		20210702

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ClearSign Technologies Corp
		CENTRAL INDEX KEY:			0001434524
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INSTRUMENTS FOR MEASUREMENT, DISPLAY, AND CONTROL [3823]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			WA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		S-8 POS
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	333-238613
		FILM NUMBER:		211070649

	BUSINESS ADDRESS:	
		STREET 1:		12870 INTERURBAN AVENUE SOUTH
		CITY:			SEATTLE
		STATE:			WA
		ZIP:			98168
		BUSINESS PHONE:		(206) 673-4848

	MAIL ADDRESS:	
		STREET 1:		12870 INTERURBAN AVENUE SOUTH
		CITY:			SEATTLE
		STATE:			WA
		ZIP:			98168

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CLEARSIGN COMBUSTION CORP
		DATE OF NAME CHANGE:	20080507
</SEC-HEADER>
<DOCUMENT>
<TYPE>S-8 POS
<SEQUENCE>1
<FILENAME>tm2121168d4_s8pos.htm
<DESCRIPTION>S-8 POS
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<P STYLE="text-align: center; margin-top: 0; margin-bottom: 0"><B>As filed with the U.S. Securities and Exchange Commission on July 2, 2021</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: right"><B>Registration No. 333-184884</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: right"><B>Registration No. 333-204129</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: right"><B>Registration No. 333-228267</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: right"><B>Registration
No. 333-238613</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: right"><B></B></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: right"><B></B>&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>UNITED STATES</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>SECURITIES AND EXCHANGE COMMISSION</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Washington, D.C. 20549</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Post-Effective Amendment No. 1 to Form S&#45;8
Registration Statement No. 333-184884</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Post-Effective Amendment No. 1 to Form S&#45;8
Registration Statement No. 333-204129</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Post-Effective Amendment No. 1 to Form S&#45;8
Registration Statement No. 333-228267</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Post-Effective Amendment No. 1 to Form S&#45;8
Registration Statement No. 333-238613</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>UNDER THE SECURITIES ACT OF 1933</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">&nbsp;</P>

<P STYLE="font: 14pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><FONT STYLE="font-size: 14pt"><B>ClearSign Technologies
Corporation</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">(Exact name of Registrant as specified in its charter)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt"><B>Washington</B></FONT></TD>
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt"><B>26-2056298</B></FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">(State or other jurisdiction of incorporation or organization)</FONT></TD>
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">(IRS Employer Identification Number)</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 5.65pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 5.65pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt"><B>12870 Interurban Avenue South, Seattle, WA</B></FONT></TD>
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt"><B>98168</B></FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">(Address of Principal Executive Offices)</FONT></TD>
    <TD STYLE="padding: 0.25pt 5.65pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">(Zip Code)</FONT></TD></TR>
  </TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B></B>&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>ClearSign Technologies Corporation 2011 Equity
Incentive Plan, as amended</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>ClearSign Technologies Corporation 2021 Equity
Incentive Plan</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">(Full title of the plan)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Brian Fike</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Chief Financial Officer</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>ClearSign Technologies Corporation</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>12870 Interurban Avenue South</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Seattle, Washington 98168</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>(206) 673-4848</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">(Name, address and telephone number, including
area code, of agent for service)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Copies to:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Nimish Patel, Esq.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Blake Baron, Esq.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Mitchell Silberberg &amp; Knupp LLP</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>2049 Century Park East, 18th Floor</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Los Angeles, California 90067</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>Phone: (310) 312-3258</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">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 &#8220;large accelerated filer,&#8221; &#8220;accelerated filer,&#8221; &#8220;smaller reporting company&#8221; and &#8220;emerging
growth company&#8221; in Rule 12b-2 of the Exchange Act.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
  <TR>
    <TD STYLE="width: 58%; font-size: 10pt"><FONT STYLE="font-size: 10pt">Large accelerated filer <FONT STYLE="font-family: Wingdings">&uml;</FONT></FONT></TD>
    <TD STYLE="width: 12%">&nbsp;</TD>
    <TD STYLE="width: 30%; font-size: 10pt"><FONT STYLE="font-size: 10pt">Accelerated filer <FONT STYLE="font-family: Wingdings">&uml;</FONT></FONT></TD></TR>
  <TR>
    <TD STYLE="font-size: 10pt"><FONT STYLE="font-size: 10pt">Non-accelerated filer <FONT STYLE="font-family: Wingdings"><FONT STYLE="font-family: Wingdings">&#120;</FONT></FONT></FONT></TD>
    <TD>&nbsp;</TD>
    <TD STYLE="font-size: 10pt"><FONT STYLE="font-size: 10pt">Smaller reporting company <FONT STYLE="font-family: Wingdings"><FONT STYLE="font-family: Wingdings">&#120;</FONT></FONT></FONT></TD></TR>

<TR>
    <TD STYLE="width: 58%">&nbsp;</TD>
    <TD STYLE="width: 12%">&nbsp;</TD>
    <TD STYLE="font-size: 10pt; width: 30%"><FONT STYLE="font-size: 10pt">Emerging growth company <FONT STYLE="font-family: Wingdings">&uml;</FONT></FONT></TD></TR>
  </TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">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 7(a)(2)(B) of the Securities Act. <FONT STYLE="font-family: Wingdings">&#168;</FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>EXPLANATORY NOTE</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">ClearSign Technologies Corporation
(the &#8220;Registrant&#8221;) has previously registered shares of the Registrant&#8217;s common stock, par value $0.0001 per share (the
 &#8220;Common Stock&#8221;), to be issued under the 2011 Equity Incentive Plan, as amended (the &#8220;2011 Plan&#8221;). In connection
with the 2011 Plan, the Registrant has previously filed with the Securities and Exchange Commission (the &#8220;SEC&#8221;) a Registration
Statement on Form S-8 on November 13, 2012 (File No. 333-184884), a Registration Statement on Form S-8 on May 13, 2015 (File No. 333-204129),
a Registration Statement on Form S-8 on November 8, 2018 (File No. 333-228267), and a Registration Statement on Form S-8 on May 22, 2020
(File No. 333-238613) (collectively, the &#8220;Registration Statements&#8221;).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">On June 17, 2021 (the &#8220;Approval
Date&#8221;), the stockholders of the Registrant approved the 2021 Equity Incentive Plan (the &#8220;2021 Plan&#8221;). Pursuant to the
terms of the 2021 Plan, the maximum number of shares of Common Stock that may be issued under the 2021 Plan shall be the sum of (i) 3,125,466
newly available shares of Common Stock (the &#8220;New Shares&#8221;), and (ii) any shares subject to stock options or similar awards
granted under the 2011 Plan as of the Approval Date that, after the Approval Date, expire or otherwise terminate without having been exercised
in full and shares issued pursuant to awards granted under the 2011 Plan as of the Approval Date that, after the Approval Date, are forfeited
to or are repurchased by the Company (the &#8220;Carryover Shares&#8221;), with the maximum number of Carryover Shares to be added to
the 2021 Plan pursuant to the 2011 Plan equal to 3,512,619 shares. As of the Approval Date, there were 3,381,369 Carryover Shares. No
further awards will be granted under the 2011 Plan as it expired on January 27, 2021.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">The Registration Statements
will cover the issuance of the Carryover Shares once they are available for issuance under the 2021 Plan. The Registration Statements
otherwise continue in effect as to the balance of the shares of Common Stock remaining available for issuance upon exercise of outstanding
awards and the following the exercise of awards previously granted under the 2011 Plan.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">Accordingly, pursuant to the
undertaking in Item 512(a)(1)(iii) of Regulation S-K that the Registrant disclose a material change in the plan of distribution as it
was originally disclosed in the Registration Statements and SEC Compliance and Disclosure Interpretation 126.43, the Registrant is filing
this Post-Effective Amendment to the Registration Statements (the &#8220;Post-Effective Amendment&#8221;) to reflect that, as of the Approval
Date, the Carryover Shares may be issued under the 2021 Plan and to file as an exhibit hereto a copy of the 2021 Plan and a new opinion
as to the validity of the shares of Common Stock that were previously issuable pursuant to the 2011 Plan. All other items of the Registration
Statements are incorporated herein by reference without change.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">Contemporaneously with the
filing of this Post-Effective Amendment, the Registrant is filing a registration statement on Form S-8 to register the New Shares that
have become available for offer or sale pursuant to the 2021 Plan. No additional securities are being registered by this Post-Effective
Amendment.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>PART II</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>INFORMATION REQUIRED IN THE REGISTRATION STATEMENT</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 3. Incorporation of Documents by Reference.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">The Registrant incorporates by reference into this
Registration Statement the following documents:</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 1in"></TD><TD STYLE="width: 0.5in">(a)</TD><TD STYLE="text-align: justify">The Registrant&#8217;s Annual Report on <A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921044241/tm211074d1_10k.htm" STYLE="-sec-extract: exhibit">Form 10-K for the fiscal year ended December 31, 2020, filed with the Commission on March 31, 2021</A>, as amended by Amendment No. 1 on <A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921059140/tm2114702d1_10ka.htm" STYLE="-sec-extract: exhibit">Form 10-K/A filed with the Commission on April 30, 2021</A>;</TD></TR></TABLE>

<P STYLE="margin-top: 0pt; margin-bottom: 0pt; font: 10pt Times New Roman, Times, Serif">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 1in"></TD><TD STYLE="width: 0.5in">(b)</TD><TD STYLE="text-align: justify">The Registrant&#8217;s Quarterly Report on <A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921067230/tm2111771d1_10q.htm" STYLE="-sec-extract: exhibit">Form 10-Q for the quarter ended March 31, 2021, filed with the Commission on May 17, 2021</A>;</TD></TR></TABLE>

<P STYLE="margin-top: 0pt; margin-bottom: 0pt; font: 10pt Times New Roman, Times, Serif">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 1in"></TD><TD STYLE="width: 0.5in">(c)</TD><TD STYLE="text-align: justify">The Registrant&#8217;s Current Reports on Form 8-K, filed with the Commission on <A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921033306/tm218997d1_8k.htm" STYLE="-sec-extract: exhibit">March 8, 2021</A>, <A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921041551/tm2110949d1_8k.htm" STYLE="-sec-extract: exhibit">March 25, 2021</A>, <A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921044798/tm2111305d1_8ka.htm" STYLE="-sec-extract: exhibit">March 31, 2021</A>,<A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921054467/tm2113920d1_8k.htm" STYLE="-sec-extract: exhibit"> April 23, 2021</A>, and <A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921083173/tm2113920d2_8k.htm" STYLE="-sec-extract: exhibit">June 21, 2021</A>; and</TD></TR></TABLE>

<P STYLE="margin-top: 0pt; margin-bottom: 0pt; font: 10pt Times New Roman, Times, Serif">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 1in"></TD><TD STYLE="width: 0.5in">(d)</TD><TD STYLE="text-align: justify"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465920039929/tm205247d1_ex4-2.htm" STYLE="-sec-extract: exhibit">The description of the Registrant&#8217;s Common Stock set forth in Exhibit 4.2 of the Registrant&#8217;s Annual Report for the fiscal year ended December 31, 2019 on Form 10-K filed with the Commission on March 30, 2020, including any future amendment or report filed for the purpose of updating such description.</A></TD></TR></TABLE>

<P STYLE="margin-top: 0pt; margin-bottom: 0pt; font: 10pt Times New Roman, Times, Serif">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">All documents subsequently
filed by the Registrant with the Commission pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as
amended, (which does not include information furnished pursuant to Item 2.02 or Item 7.01 of any Current Report on Form 8-K, unless expressly
stated therein) after the date of this Registration Statement, but prior to the filing of a post-effective amendment to this Registration
Statement which indicates that all securities offered by this Registration Statement have been sold or which deregisters all such securities
then remaining unsold, shall be deemed to be incorporated by reference into this Registration Statement. Each document incorporated by
reference into this Registration Statement shall be deemed to be a part of this Registration Statement from the date of the filing of
such document with the Commission until the information contained therein is superseded or updated by any subsequently filed document
which is incorporated by reference into this Registration Statement.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 4. Description of Securities.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 5. Interests of Named Experts and Counsel.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 6. Indemnification of Directors and Officers.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">Sections 23B.08.500 through
23.B.08.603 of the Washington Business Corporation Act (the &#8220;WBCA&#8221;) authorize a court to award, or a corporation&#8217;s board
of directors to grant, indemnification to directors and officers on terms sufficiently broad to permit indemnification under certain circumstances
for liabilities arising under the Securities Act of 1933, as amended (the &#8220;Securities Act&#8221;). Section 23B.08.320 of the WBCA
authorizes a corporation to limit a director&#8217;s liability to the corporation or its shareholders for monetary damages for acts or
omissions as a director, except in certain circumstances involving intentional misconduct, knowing violations of law or illegal corporate
loans or distributions, or any transaction from which the director personally receives a benefit in money, property or services to which
the director is not legally entitled.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">The Registrant&#8217;s Articles
of Incorporation provide that, to the fullest extent permitted by Washington law, the Registrant&#8217;s directors will not be liable
to the Registrant or its shareholders for monetary damages. This provision, however, does not eliminate or limit liability for acts or
omissions that involve intentional misconduct or a knowing violation of law by a director, for conduct violating WBCA section 23B.08.310
(approval of an unlawful distribution) or for any transaction from which the director will personally receive a benefit in money, property,
or services to which the director is not legally entitled. Pursuant to section 23B.08.52 of the WBCA, because the Registrant&#8217;s Articles
of Incorporation do not limit the obligation, the Registrant must indemnify a director who was wholly successful, on the merits or otherwise,
in the defense of any proceeding to which the director was a party because of being a director against reasonable expenses incurred by
the director in connection with the proceeding.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">The Registrant&#8217;s Bylaws
further provide that each person who was, is or is threatened to be made a party to or is otherwise involved in any threatened, pending
or completed action, suit, claim or proceeding, whether civil, criminal, administrative or investigative and whether formal or informal,
by reason of the fact that he or she is or was a director or officer of the Registrant or was serving at the Registrant&#8217;s request
as a director, officer, partner, trustee, employee or agent of another entity, shall be indemnified and held harmless against all losses,
claims, damages, liabilities and expenses actually and reasonably incurred or suffered in connection with the proceeding.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>




<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">This indemnification right continues even after
the individual has ceased to be a director or officer or to serve at the Registrant&#8217;s request as a director, officer, partner, trustee,
employee or agent of another entity. However, if the person indemnified initiates the proceeding, he or she shall be entitled to indemnification
only if the proceeding was authorized or ratified by the Registrant&#8217;s board of directors. No indemnification will be provided for
acts or omissions finally adjudged to be intentional misconduct or a knowing violation of law, for conduct finally adjudged to be in violation
of WBCA section 23B.08.310, for any transaction with respect to which it was finally adjudged that the indemnitee personally received
a benefit in money, property or services to which the indemnitee was not legally entitled or if the Registrant is otherwise prohibited
by applicable law from paying indemnification. The Registrant must advance expenses to an indemnitee for an indemnification obligation
so long as the Registrant receives an undertaking by or on behalf of the indemnitee to repay all amounts so advanced if it is determined
by a final judicial decision from which there is no further right to appeal that the indemnitee is not entitled to be indemnified.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">Under the Registrant&#8217;s
Director and Officer Insurance Policy, directors and officers are provided liability coverage of $5 million subject to retention. The
policy has a one year term with annual renewal possible. The policy can be terminated by the insured if there is a merger or acquisition
which includes a change in ownership of 50% of the voting shares. Upon such an occurrence the insurer may elect to cancel the policy.
The Registrant may elect to then obtain &#8220;run off&#8221; insurance for a period of between one and six years at a cost of between
125% and 225% of the initial policy premium. The policy is a claim made policy. It covers only those claims made during the policy term.
If an act giving rise to a claim occurs during the policy term, but the claim is not reported within 60 days of the termination or expiration
policy, the claim will not be covered.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">The Registrant has entered
into, and will enter into in the future, indemnification agreements with the individuals who serve as its officers and directors. Pursuant
to these agreements, the Registrant will indemnify officers and directors who are made parties to, or threatened to be made parties to,
any proceeding by reason of the fact that they are or were officers or directors, or are or were serving at the Registrant's request as
a director, officer, employee, or agent of another entity. The agreements require the Registrant to indemnify its officers and directors
against all expenses, judgments, fines and penalties actually and reasonably incurred by them in connection with the defense or settlement
of any such proceeding, subject to the terms and conditions of the agreements.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; background-color: white"><B>Item 7. Exemption from Registration Claimed.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; background-color: white"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in; background-color: white">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in; background-color: white">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; background-color: white"><B>Item 8. Exhibits.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; background-color: white">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt; text-align: center; background-color: white"><B>EXHIBIT INDEX</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
  <TR>
    <TD STYLE="vertical-align: bottom; border-bottom: black 1pt solid; padding-bottom: 0.5pt; width: 10%"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><FONT STYLE="font-size: 10pt"><B>Exhibit</B></FONT></P>
    <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><FONT STYLE="font-size: 10pt"><B>No.</B></FONT></P></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom; padding-bottom: 1pt; width: 1%"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; border-bottom: black 1pt solid; vertical-align: bottom; padding-bottom: 0.5pt; text-align: center; width: 89%"><FONT STYLE="font-size: 10pt"><B>Description
    of Document</B></FONT></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465919063298/tm1919478d1_10q.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">4.1</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465919063298/tm1919478d1_10q.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">Articles of Incorporation of ClearSign Technologies Corporation (1)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420411064058/v240232_s1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">4.2</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420411064058/v240232_s1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">Bylaws of ClearSign Technologies Corporation (2)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420419030688/tv523444_8k.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">4.2.1</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420419030688/tv523444_8k.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">Amendment to Bylaws (3)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420415012243/v400802_10k.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">4.3</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420415012243/v400802_10k.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">Form of Common Stock Certificate (4)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="tm2121168d4_ex5-1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">5.1.</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="tm2121168d4_ex5-1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">Opinion of Mitchell Silberberg &amp; Knupp LLP (filed herewith)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="tm2121168d4_ex23-1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">23.1.</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="tm2121168d4_ex23-1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">Consent of Gumbiner Savett Inc. (filed herewith)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="tm2121168d4_ex5-1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">23.2.</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="tm2121168d4_ex5-1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">Consent of Mitchell Silberberg &amp; Knupp LLP (included in Exhibit
    5.1)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420411064058/v240232_s1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">99.1</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000114420411064058/v240232_s1.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">ClearSign Technologies Corporation 2011 Equity Incentive Plan (2)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921062561/tm2114678d1_def14a.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">99.2</FONT></A></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><A HREF="http://www.sec.gov/Archives/edgar/data/1434524/000110465921062561/tm2114678d1_def14a.htm" STYLE="-sec-extract: exhibit"><FONT STYLE="font-size: 10pt">ClearSign Technologies Corporation 2021 Equity Incentive Plan (5)</FONT></A></TD>
    </TR>
  <TR STYLE="font: 10pt Times New Roman, Times, Serif">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top; text-align: center"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: bottom"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; vertical-align: top"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></TD>
    </TR>
  </TABLE>
<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">(1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Incorporated herein by
reference from the Registrant&#8217;s Form 10-Q for the quarter ended September 30, 2019 filed with the Securities and Exchange Commission
on November 13, 2019.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>




<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">(2)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Incorporated herein by
reference from the Registrant&#8217;s registration statement on Form S-1, as amended, file number 333-177946, originally filed with the
Securities and Exchange Commission on November 14, 2011.</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">(3)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Incorporated herein by
reference from the Registrant&#8217;s Current Report on Form 8-K filed with the Securities and Exchange Commission on June 12, 2019.</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">(4)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Incorporated herein by
reference from the Registrant&#8217;s Annual Report on Form 10-K filed with the Securities and Exchange Commission on February 26, 2015.</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">(5)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Incorporated herein by
reference from Appendix A to the Registrant&#8217;s Proxy Statement on Schedule 14A, filed with the Securities and Exchange Commission
on May 7, 2021.</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 9. Undertakings.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">(a) The undersigned Registrant
hereby undertakes:</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">1. To file, during any period
in which offers or sales are being made, a post-effective amendment to this registration statement:</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 1.5in"></TD><TD STYLE="width: 0.5in">i.</TD><TD STYLE="text-align: justify">to include any prospectus required by section 10(a)(3) of the Securities Act;</TD></TR></TABLE>

<P STYLE="margin-top: 0pt; margin-bottom: 0pt; font: 10pt Times New Roman, Times, Serif">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 1.5in"></TD><TD STYLE="width: 0.5in">ii.</TD><TD STYLE="text-align: justify">to reflect in the prospectus any facts or events arising after the effective date of the registration
statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change
in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities
offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or
high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule
424(b) if, in the aggregate, the changes in volume and price represent no more than 20% change in the maximum aggregate offering price
set forth in the &#8220;Calculation of Registration Fee&#8221; table in the effective registration statement; and</TD></TR></TABLE>

<P STYLE="margin-top: 0pt; margin-bottom: 0pt; font: 10pt Times New Roman, Times, Serif">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 1.5in"></TD><TD STYLE="width: 0.5in">iii.</TD><TD STYLE="text-align: justify">to include any material information with respect to the plan of distribution not previously disclosed
in the registration statement or any material change to such information in the registration statement;</TD></TR></TABLE>

<P STYLE="margin-top: 0pt; margin-bottom: 0pt; font: 10pt Times New Roman, Times, Serif">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">provided, however, that paragraphs
(a)(1)(i) and (a)(1)(ii) of this section do not apply if the registration statement is on Form S-8, and the information required to be
included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the Registrant
pursuant to section 13 or section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration
statement.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">2. That, for the purpose of
determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide
offering thereof.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">3. To remove from registration
by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 1in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">(b) The undersigned Registrant
hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the Registrant&#8217;s annual
report pursuant to section 13(a) or section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee
benefit plan&#8217;s annual report pursuant to section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference
in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering
of such securities at that time shall be deemed to be the initial bona fide offering thereof.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>




<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">(c) Insofar as indemnification
for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the Registrant pursuant
to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission
such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer
or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer
or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the
matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification
by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>SIGNATURES</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">Pursuant to the requirements
of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements
for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized,
in the City of Seattle, State of Washington, on July 2, 2021.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding: 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><B>CLEARSIGN TECHNOLOGIES CORPORATION</B></FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt; width: 50%">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt; width: 3%">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt; width: 47%">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">By:</FONT></TD>
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 0.25pt 0.5pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Colin James Deller</I></FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Colin James Deller, Chief Executive Officer</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt; font-size: 10pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt; font-size: 10pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 0.25pt 0.5pt; font-size: 10pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">By</FONT></TD>
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 0.25pt 0.5pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Brian G. Fike</I></FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Brian G. Fike, Chief Financial Officer</FONT></TD></TR>
  </TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 40.8pt">&nbsp;</P>




<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; margin-bottom: 0pt; text-align: center"><B>POWER OF ATTORNEY</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center; text-indent: 40.8pt">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 40.8pt">We, the undersigned officers
and directors of ClearSign Technologies Corporation (the &#8220;Company&#8221;), hereby constitute and appoint Colin James Deller and
Brian G. Fike and each of them, the true and lawful agents and attorneys-in-fact of the undersigned with full power and authority in said
agents and attorneys-in-fact, and in any one or more of them, to sign for the undersigned and in their respective names as an officer/director
of the Company, a registration statement on Form S-8 (or other appropriate form) relating to the offer and sale of common stock of the
Company pursuant to this Registration Statement and any amendments thereto and file the same, with all exhibits thereto and other documents
in connection therewith, with the Securities and Exchange Commission, and with full power of substitution; hereby ratifying and confirming
all that each of said attorneys-in-fact, or his/her substitute or substitutes, may do or cause to be done by virtue hereof.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 40.8pt">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">Pursuant to the requirements
of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates
indicated:</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
  <TR STYLE="vertical-align: top">
    <TD STYLE="width: 31%; padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt"><B>Signature</B></FONT></TD>
    <TD STYLE="width: 2%; padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="width: 45%; padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt"><B>Title</B></FONT></TD>
    <TD STYLE="width: 2%; padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="width: 20%; padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt"><B>Date</B></FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 7.75pt 0.5pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Colin James Deller</I></FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 4.5pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Chief Executive Officer and Director</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">July 2, 2021</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Colin James Deller</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">(Principal Executive Officer)</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 7.75pt 0.5pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Brian G. Fike</I></FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Chief Financial Officer</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">July 2, 2021</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Brian G. Fike</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">(Principal Financial and Accounting Officer)</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 7.75pt 0.5pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Robert T. Hoffman Sr.</I></FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Director</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">July 2, 2021</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Robert T. Hoffman Sr.</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 7.75pt 0.5pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Judith S. Schrecker</I></FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Director</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">July 2, 2021</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Judith S. Schrecker</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 7.75pt 0.5pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Susanne L. Meline</I></FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Director</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">July 2, 2021</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Susanne L. Meline</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1pt solid; padding: 0.25pt 7.75pt 0.5pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt"><I>/s/ Bruce A. Pate</I></FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Director</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 10pt">July 2, 2021</FONT></TD></TR>
  <TR STYLE="vertical-align: top">
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt; font-size: 10pt"><FONT STYLE="font-size: 10pt">Bruce A. Pate</FONT></TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD>
    <TD STYLE="padding: 0.25pt 7.75pt 0.25pt 0.25pt">&nbsp;</TD></TR>
  </TABLE>
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<DOCUMENT>
<TYPE>EX-5.1
<SEQUENCE>2
<FILENAME>tm2121168d4_ex5-1.htm
<DESCRIPTION>EXHIBIT 5.1
<TEXT>
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<P STYLE="margin: 0">&nbsp;</P>

<P STYLE="text-align: right; margin: 0"><B>Exhibit 5.1</B></P>

<P STYLE="margin: 0">&nbsp;</P>

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    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid; font-size: 10pt"><IMG SRC="tm2121168d4_ex5-1img001.jpg" ALT="" STYLE="height: 36px; width: 110px"></TD></TR>
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    <TD STYLE="width: 51%">
    <P STYLE="font: small-caps 14pt Times New Roman, Times, Serif; margin: 0pt 0">Mitchell Silberberg <FONT STYLE="font-family: Times New Roman, Times, Serif">&amp;</FONT>
    Knupp llp</P>
    <P STYLE="font: small-caps 10pt Times New Roman, Times, Serif; margin: 0pt 0">A Law Partnership Including Professional Corporations</P></TD>
    <TD STYLE="width: 49%; padding-right: -1.45pt; padding-left: 2.15pt; text-align: right; font-size: 10pt">&nbsp;</TD></TR>
  </TABLE>

<P STYLE="margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">July 2, 2021</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Board of Directors<BR>
ClearSign Technologies Corporation</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">12870 Interurban Avenue South</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Seattle, Washington 98168</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
  <TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="font-size: 10pt"><FONT STYLE="font-family: Times New Roman, Times, Serif; font-size: 10pt"><B>Re:</B></FONT></TD>
    <TD STYLE="font-size: 10pt; text-align: justify"><FONT STYLE="font-family: Times New Roman, Times, Serif; font-size: 10pt"><B><U>Post-Effective Amendment to Registration Statements on Form S-8</U></B></FONT></TD></TR>
  </TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">Ladies and Gentlemen:</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">We have examined the Post-Effective Amendment to
the Registration Statements on Form&nbsp;S-8&nbsp;to be filed by you with the Securities and Exchange Commission on July 2, 2021 (the
 &#8220;<U>Registration Statement</U>&#8221;) in connection with the registration under the Securities Act of 1933, as amended, which you
are filing with respect to the Carryover Shares (as defined below) authorized for issuance under the 2011 Plan (as defined below).</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">The Registration Statement reflects that on June
17, 2021 (the &#8220;<U>Approval Date</U>&#8221;), the stockholders of the ClearSign Technologies Corporation, a Washington corporation
(the &#8220;<U>Company</U>&#8221;) approved the 2021 Equity Incentive Plan (the &#8220;<U>2021 Plan</U>&#8221;). Pursuant to the terms
of the 2021 Plan, the maximum number of shares of the Company&#8217;s common stock, par value $0.0001 per share (&#8220;<U>Common Stock</U>&#8221;)
that may be issued under the 2021 Plan shall be the sum of (i) 3,125,466 newly available shares of Common Stock, and (ii) any shares subject
to stock options or similar awards granted under the 2011 Plan as of the Approval Date that, after the Approval Date, expire or otherwise
terminate without having been exercised in full and shares issued pursuant to awards granted under the 2011 Plan as of the Approval Date
that, after the Approval Date, are forfeited to or are repurchased by the Company (the &#8220;<U>Carryover Shares</U>&#8221;), with the
maximum number of Carryover Shares to be added to the 2021 Plan pursuant to the 2011 Plan equal to 3,512,619 shares of Common Stock. The
total number of shares of Common Stock of the Company authorized for issuance under the 2021 Plan is 6,638,085.</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">For purposes of this opinion letter, we have examined
the 2011 Plan, the 2021 Plan, the Registration Statement, the Articles of Incorporation and the Bylaws of the Company, as amended or restated,
the proceedings and other actions of the Company that provide for the issuance of the Carryover Shares, and such other documents and matters
as we have deemed necessary for purposes of rendering this opinion. As your legal counsel, we have examined the proceedings taken and
are familiar with the proceedings proposed to be taken by you in connection with the sale and issuance of the Carryover Shares under the
2021 Plan. We have assumed the authenticity of all documents submitted to us as originals, the conformity to originals of all documents
submitted to us as certified or photostatic copies and the authenticity of the originals of all documents submitted to us as copies. We
have also assumed the legal capacity of all natural persons who have executed documents examined by us, the genuineness of all signatures
on all documents examined by us, the authority of such persons signing on behalf of the parties thereto other than the Company and the
due authorization, execution and delivery of all documents by the parties thereto other than the Company. In rendering the opinion set
forth below, we have assumed that certificates evidencing the Carryover Shares will be signed by the authorized officers of the Company
and registered by the transfer agent and registrar and will conform to the specimen certificate for the Common Stock. In addition, we
have assumed that the resolutions of the Company&#8217;s board of directors or its applicable committee authorizing the Company to issue
and deliver the Carryover Shares will be in full force and effect at all times at which such Carryover Shares are issued and delivered
by the Company, and that the Company will take no action inconsistent with such resolutions.</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">It is our opinion that, when issued and sold in
the manner referred to in the 2021 Plan and pursuant to the standard practices which accompany any sale under the 2021 Plan, the Carryover
Shares will be legally and validly issued, fully paid, and nonassessable.</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; text-align: justify; margin: 0pt 0; text-indent: 0.5in"></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="text-align: justify; font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">We consent to the use of
this opinion as an exhibit to the Registration Statement and further consent to the use of our name wherever it appears in the
Registration Statement and any amendment thereto. In giving our consent we do not hereby admit that we are in the category of
persons whose consent is required under Section 7 of the Securities Act of 1933, as amended.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" STYLE="border-collapse: collapse; width: 100%">
  <TR STYLE="vertical-align: bottom">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; width: 50%">&nbsp;</TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; width: 50%">Sincerely,</TD></TR>
  <TR STYLE="vertical-align: bottom">
    <TD COLSPAN="2" STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: bottom">
    <TD STYLE="font: italic 10pt Times New Roman, Times, Serif">&nbsp;</TD>
    <TD STYLE="font: italic 10pt Times New Roman, Times, Serif">/s/ Mitchell Silberberg &amp; Knupp LLP</TD></TR>
  <TR STYLE="vertical-align: bottom">
    <TD COLSPAN="2" STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</TD></TR>
  <TR STYLE="vertical-align: bottom">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</TD>
    <TD STYLE="font: 10pt Times New Roman, Times, Serif">Mitchell Silberberg &amp; Knupp LLP</TD></TR>
  </TABLE>


<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0 0pt 3in">&nbsp;</P>



<P STYLE="margin: 0"></P>

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<DOCUMENT>
<TYPE>EX-23.1
<SEQUENCE>3
<FILENAME>tm2121168d4_ex23-1.htm
<DESCRIPTION>EXHIBIT 23.1
<TEXT>
<HTML>
<HEAD>
     <TITLE></TITLE>
</HEAD>
<BODY STYLE="font: 10pt Times New Roman, Times, Serif">

<P STYLE="text-align: right; margin: 0"><B>Exhibit 23.1</B></P>

<P STYLE="margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><FONT STYLE="font-size: 10pt"><IMG SRC="tm2121168d4_ex23-1img001.jpg" ALT="11-023-gs-special-report-logo-v1-01" STYLE="height: 94px; width: 235px"></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING
FIRM</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">We consent to the incorporation by reference in the Post-Effective
Amendment No. 1 to Registration Statement Nos. 333-184884, 333-204129, 333-228267, and 333-238613 on Form S-8 of ClearSign Technologies
Corporation and subsidiary (the &ldquo;Company&rdquo;) of our report dated March 31, 2021 with respect to the audited consolidated financial
statements of the Company for the years ended December 31, 2020 and 2019, which is contained in the annual report on Form 10-K filed on
March 31, 2021.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">/s/ Gumbiner Savett Inc.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">July 2, 2021</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Santa Monica, California</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

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end
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
