SEATTLE, Oct. 18, 2019 — ClearSign Combustion Corporation (Nasdaq: CLIR) (“ClearSign” or the “Company”), an emerging leader in industrial combustion technologies that improve energy and operational efficiency while dramatically reducing emissions, announces that the company has received a Purchase Order from ExxonMobil to perform early engineering and installation planning regarding a trial installation of the company’s ClearSign Core process burners at one of their Gulf Coast refineries.

This order is the next step in the process for the Company to showcase ClearSign Core technology’s best-in-classNOx emissions and for ExxonMobil to assess applicability across its process heater fleet. The engineering follows the previously announced qualification program that the Company performed at their State-of-the-Art Seattle R&D facility. That testing was an evaluation over a broad range of typical conditions, including variations in fuel heating values, turndown, and excess air.

“We are delighted and encouraged by this highly significant order, and the ongoing engagement and interest from ExxonMobil,” said Jim Deller, Ph.D, CEO of ClearSign. “This engineering order is one of the final steps prior to qualifying our ClearSign Core process burner technology for use in an ExxonMobil refinery, and is a significant milestone for our company in the process of demonstrating our technology with a supermajor at their facility. This is a culmination of months of thorough evaluation and coordination between our team and the Research and Engineering team at ExxonMobil. The specific site and location has been selected and we look forward to continuing to support ExxonMobil’s evaluation of our ClearSign Core technology.”

About ClearSign Combustion Corporation

ClearSign Combustion Corporation designs and develops products and technologies for the purpose of improving key performance characteristics of combustion systems, including operational performance, energy efficiency, emission reduction and overall cost-effectiveness. Our patented technologies, embedded in established OEM products as ClearSign Core™ enhance the performance of combustion systems in a broad range of markets, including the energy (upstream oil production and down-stream refining), commercial/industrial boiler, chemical, petrochemical, and power industries. For more information, please visit www.clearsign.com.

Cautionary note on forward-looking statements

All statements in this press release that are not based on historical fact are “forward-looking statements.” You can find many (but not all) of these statements by looking for words such as “approximates,” “believes,” “hopes,” “expects,” “anticipates,” “estimates,” “projects,” “intends,” “plans,” “would,” “should,” “could,” “may,” “will” or other similar expressions. While management has based any forward-looking statements included in this press release on its current expectations, the information on which such expectations were based may change. These forward-looking statements rely on a number of assumptions concerning future events and are subject to a number of risks, uncertainties and other factors, many of which are outside of our control, that could cause actual results to materially differ from such statements. Such risks, uncertainties and other factors include, but are not limited to, general business and economic conditions, the performance of management and our employees, our ability to obtain financing, competition, whether our technology will be accepted and other factors identified in our Annual Report on Form 10-K filed with the Securities & Exchange Commission and available at www.sec.gov and other factors that are detailed in our periodic and current reports available for review at www.sec.gov. Furthermore, we operate in a competitive environment where new and unanticipated risks may arise. Accordingly, investors should not place any reliance on forward-looking statements as a prediction of actual results. We disclaim any intention to, and undertake no obligation to, update or revise forward-looking statements to reflect events or circumstances that subsequently occur or of which we hereafter become aware.

SOURCE ClearSign Combustion Corporation

For further information: Investor Relations: Matthew Selinger, Firm IR Group for ClearSign, +1 415-572-8152, mselinger@firmirgroup.com