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                                                            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.
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