What changed in this filing

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Item 1. Business

2026-03-31 compared with 2025-03-31 · 148 added, 102 removed, 258 unchanged (49% of the section changed)

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In addition, because the flame volumes in heaters utilizing ClearSign Core TM technology are typically small, heaters using our technology are expected to operate at a lower cost, have increased productivity, and require less maintenance and downtime compared to heaters that operate with enlarged flames produced by traditional low NOx burners.

The flames in a ClearSign Core TM system are established from a predominantly premixed stream of fuel, combustion air and flue gasses stabilized on a downstream structure that promotes turbulence and ignition with minimal “bulking up.” In comparison, flames resulting from the traditional legacy process of slow mixing of the fuel and air, and dilutive inert flue gasses have a much larger size.

The flames in a ClearSign Core TM system are established from a predominantly premixed stream of fuel, combustion air and/or flue gasses stabilized on a downstream structure that promotes turbulence and ignition with minimal “bulking up.” In comparison, flames resulting from the traditional legacy process of slow mixing of the fuel and air, and dilutive inert flue gasses have a much larger size.

With a lower volume flame in a ClearSign Core TM system, surfaces in the heater or boiler experience less touching by the flame and it is anticipated that our systems can virtually eliminate flame impingement.

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The secondary potential market for our sensing technology is outside of the typical combustion industry and includes transportation industries.

We are collaborating with Narion Corporation to further develop our technology for this industry, which

allows us to incur minimal costs while pursuing this market opportunity.

We are collaborating with Narion Corporation (“Narion”) to further develop our technology for this industry, which allows us to incur minimal costs while pursuing this market opportunity.

While use of this fundamental technology in applications intended for transportation markets is proven, the development and refinement of specific products, obtaining the certifications required for commercial deployment and establishing an efficient manufacturing source and channels to market will take some time, and we cannot assure that these goals will be achieved.

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The 8-hour ground-level ozone regulations have been reduced from 80 parts per billion (“ppb”) in 1997, to 75 ppb in 2008, and 70 ppb in 2015, with the requirement of realizing these levels approximately 20 years following the year of legislation.

We have noted that local air quality districts designated by the EPA as “severe non-attainment zones” in California and Texas have undertaken a review of their air pollutant emissions regulations.

Local air quality districts in California and Texas designated as “severe non-attainment zones” by the EPA have undertaken a review of their air pollutant emissions regulations.

These reviews are ongoing, in most regions, but two important regions have recently amended their local regulations to improve air quality.

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And, in November of 2021, the greater Los Angeles area also revised its regulations.

These revised regulations substantially reduced target emissions for process heaters, boilers and other similar equipment pursuant to a new and comprehensive Best Available Retrofit Control Technology (“BARCT”) analysis, which we believe will result in an increased demand for our services and products.

These revised regulations substantially reduced target emissions for process heaters, boilers and other similar equipment pursuant to a new and comprehensive Best Available Retrofit Control Technology (“BARCT”) analysis, which we believe will continue to generate an increased demand for our services and products.

On February 2, 2024, the South Coast Air Quality Management District of California (“SCAQMD”) as part of its periodic public participation process to enhance existing Best Available Control Technologies (“BACT”) determinations, assessed the process burner performance of our ClearSign Core ™ burner technology in certain currently operating customer installations.

As a result of this assessment, SCAQMD approved new BACT performance guidelines for both single and multi-burner configurations.

As a result of this

assessment, SCAQMD approved new BACT performance guidelines for both single and multi-burner configurations.

BACT guidelines are periodically updated by SCAQMD to reflect advancements in technology and to ensure affected equipment utilize the most efficient technologies.

While the establishment of a new BACT benchmark does not specifically endorse ClearSign or our

products, it does establish a limit in the industry that favors our products.

While the establishment of a new BACT benchmark does not specifically endorse us or our products, it does establish a limit in the industry that favors our products.

According to SCAQMD, BACT is the most stringent emission limitation or control technique for a class and category of equipment that is “Achieved in Practice,” or “Contained in a State Implementation Plan” (“SIP”), or “Technologically Feasible.”

On October 3, 2025 the Texas Commission on Environmental Quality (“TCEQ”) delivered a proposal to the EPA outlining changes to their local regulations to maintain compliance with the Federal Clean Air Act (“FCAA”).

Among the proposed changes, the TCEQ has recommended the implementation of fee program to fine major NOx emitters.

As of the date of this report, the TCEQ rule change has not been approved by the EPA, but we believe this regulation change, if approved, will ultimately incentivize our customers to seek NOx reduction technologies for their current and future operations.

In addition, new regulations are starting to be adopted with respect to the NOx emissions of enclosed ground flares, which historically have not been viewed as a source of NOx emissions or subject to the same level of regulation.

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There are multiple ClearSign Core TM flare applications now operational in California with NOx emissions below the levels required by new regulations.

During 2025, we experienced an increase in low NOx flare inquiries, which we believe were driven by these new regulations, and as a result we received multiple purchases orders from a California energy company.

In addition, we believe that current emissions standards in Europe, the Middle East, parts of Asia and Canada will continue to become stricter as these jurisdictions seek to achieve cleaner air.

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Because hydrogen burns at a higher temperature than most other fuel gasses, it tends to create more NOx emissions.

ClearSign Core TM burners have demonstrated the ability to burn fuels with up to 80% hydrogen while still controlling NOx emissions to meet required regulatory levels.

We believe that we can extend the capability of our ClearSign Core TM technology to burn “pure” hydrogen fuel.

During 2025, as part of our Department of Energy (“DOE”) grant to develop an ultra-low NOx hydrogen burner, we successfully demonstrated a new revision of our ClearSign Core TM burner burning “pure” hydrogen fuel in an industrial scale test heater, while still controlling NOx emissions to levels commensurate with applicable regulatory requirements.

Our Proprietary Technology

ClearSign Core TM Burner Technology

The name “ClearSign Core” was adopted to describe the inclusion of ClearSign’s burner technology in the products of original equipment manufacturers (“OEM”).

Including our technology in OEM burner products enables us to leverage our technology by providing OEMs with the ability to offer a new product range with our technologies’ unique capabilities and differentiated product performance.

The name “ClearSign Core” was adopted to describe the potential inclusion of ClearSign’s burner technology in the products of original equipment manufacturers (“OEM”).

This supports our strategy of delivering product through collaborative partnerships in which we combine the value and performance of our technology with the established industry credentials, manufacturing capabilities and standard equipment designs of our partners.

Including our technology in OEM products enables us to deliver technology efficiently to our customers, and our collaborative partners by providing the ability to offer differentiated products while utilizing their established production methods.

Our ClearSign Core TM burner technology consists of an industrial burner body and a downstream flame stabilizing structure made of either porous ceramic or metal.

When the unreacted mixture of gaseous fuel and air is directed at the flame stabilizing structure, the mixture ignites and the flame forms either within or immediately downstream from the structure itself.

When the unreacted mixture of gaseous fuel and air or induced furnace gasses is directed at the flame stabilizing structure, the mixture ignites and the flame forms either within or immediately downstream from the structure itself.

Because the fuel and air have more time to become a homogeneous mixture, NOx-forming hot spots and chemistry typically produced by such hot spots is reduced.

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For example, we believe our ClearSign Core TM products, without any external fans or associated power, can significantly reduce the harmful emission of NOx to levels of 5 ppm or below, depending on the application.

The shorter flame in a ClearSign Core product can also potentially allow a furnace to operate at a higher capacity.

The shorter flame in a ClearSign Core TM product can also potentially allow a furnace to operate at a higher capacity.

We believe that heaters using the ClearSign Core TM will be able to remain in operation for an extended time before the need for maintenance as its flame structure and heat transfer profile minimize the possibility of flame impingement, reduce the likelihood of carbon deposits forming on the inside surfaces of the process tubes (coking) and reduce the likelihood of process tube failure all while operating with enhanced thermal efficiency.

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The product was designed to enable quick and easy installation in single burner or multi-burner heaters or furnaces.

We believe that the simplicity of the actions required to retrofit refinery process heaters with the ClearSign Core TM technology, and the potential ability to install these burners will potentially contribute to demand for our ClearSign Core TM process burners.

We believe that the simplicity of the actions required to retrofit refinery process heaters with the ClearSign Core TM technology will potentially contribute to demand for our ClearSign Core TM process burners.

ClearSign Core TM Boiler Burner Technology

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Our ClearSign Core TM flaring technology incorporates the same mechanisms as our burner technology, namely directing the fuel gas (typically waste gas), into an air stream with that air and gas mixture forming a flame stabilized downstream on a flame stabilizing structure.

This technology has been configured into standard modular designs that can be used individually, or in combination, to provide a flare product with extremely low NOx emissions.

We have designed standardized flare configurations with standard firing capacities that can be combined in varying quantities to produce flares with different firing rates.

This technology has been configured into standard designs that can be used to provide a flare product with extremely low NOx emissions.

We have also designed standardized flare system configurations that enable us to leverage our specialty flare burner technology to provide high value flare systems, including controls components and stack elements.

We believe that expanding our scope to include complete or partial systems will enable us to significantly increase the revenue and profit from our flare product sales.

ClearSign Eye Flame Sensor

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Unlike the traditional technology, called “flame rods,” the ClearSign Eye sensing electrodes do not need to make contact with the flame.

We are continuing to pursue “first adopter” installation opportunities for this patented sensing technology.

We are in the process of commissioning some “first adopter” installations of this patented sensing technology through a pilot program to assess the sensor’s capabilities in industrial scale heaters.

We have multiple options open to us as channels to market, one of which includes manufacturing the sensors ourselves as an OEM and selling them to customers either directly or indirectly through intermediaries, and another being licensing.

We believe our sensing technology is valuable because it potentially provides a very reliable alternative or replacement technology for critical industrial burner safety equipment.

The currently available flame sensors are unreliable and require frequent maintenance.

Our flame sensors can potentially be used with other combustion equipment such as flares, thermal oxidizer burners and boiler burners.

We believe that the current available flame sensors are unreliable and require frequent maintenance.

As a result, we believe that our sensing technology is valuable because it potentially provides a very reliable alternative or replacement technology for critical industrial burner safety equipment.

Our flame sensors can also potentially be used with other combustion equipment such as flares, thermal oxidizer burners and boiler burners.

Our sensing technology can detect the capacitance of a flame while being physically outside of the flame envelope.

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To date, we have deployed our ClearSign Core TM technology through retrofits and replacements of existing burners and complete replacement units in the case of our process burner and boiler burner products.

Retrofits often involve engineering around an existing burner architecture that can complicate the ClearSign Core TM burner installation, whereas replacements are more straightforward and more amenable to being sold and installed by third parties, enabling more expansive channels to market.

Retrofits often involve engineering around an existing burner and heater architecture that can complicate the ClearSign Core TM burner installation, whereas replacements are more straightforward and more amenable to being sold and installed by third parties, enabling more expansive channels to market.

Because of this, we have focused the development of our technology to provide designs that can be included into our prospective customers’ equipment as self-contained modules or assemblies rather than projects involving the re-engineering of existing burner systems.

In this form, we believe that the ClearSign Core TM burner technology is ideally suited for installation into new heaters and burner replacements, including heater and furnaces requiring large quantities of burners.

In addition, this strategy also provides for simple new burner installations, or burner replacements to reduce emissions in boilers ranging from small fire tube boilers to large water tube boilers.

We have also developed the ClearSign Core TM flare technology into similar repeatable forms to aid its inclusion in standard industry installations on a commercial scale with multiple installations now operational in California.

In this form, we believe that the ClearSign Core TM burner technology is ideally suited for installation into new heaters and as burner replacements into existing heaters, including heaters and furnaces requiring large quantities of burners.

In addition, this strategy also provides for simple new burner installations, or burner replacements to reduce emissions in boilers ranging from small fire tube boilers to potentially large water tube boilers.

We have also developed the ClearSign Core TM flare technology into similar repeatable forms to aid its inclusion in typical industry installations or as complete flaring systems.

For simplification and marketing, we have adopted the term “ClearSign Core” to refer to the inclusion of our standardized proprietary combustion technology into a variety of combustion equipment types including, but not limited to, process heater burners, boiler burners, burners for thermal oxidizers and flares.

Earlier ClearSign technology-based heater retrofits, in which a continuous ceramic “wall” was suspended above the existing burners, also continue to operate, and are referred to as “Duplex” technology.

Although the combustion controlling principles of both the “ClearSign Core” and “Duplex” technologies are the same, ClearSign Core TM products have standardized technology and we believe they are easier to use and have a different channel to market.

ClearSign Core TM burners currently operate in multiple boilers, heaters and flares and meet new compliance standards enacted by California air authority.

Although the combustion controlling principles of both the “ClearSign Core” and “Duplex” technologies are the same, ClearSign Core TM products have standardized technology that we believe are easier to use and install, and which also enables diversified channels to market.

ClearSign Core TM burners currently operate in multiple boilers, heaters and flares and meet new compliance standards enacted by state air authorities.

We also have products in commercial use in Europe.

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The industries using our technology take a conservative approach to adopting new technology and place significant reliance on references from existing customers when selecting new equipment.

A major focus of our current business development activities is to make early sales and build our reference list in both the process burner and boiler burner industries.

A major focus of our current business development activities is to make early sales and build our reference list in the process burner, flare, and boiler burner industries.

We also seek to provide comprehensive technical support to our sales efforts as well as demonstrate our technology and products in operation.

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ClearSign Core Technology Product Applications

To date, we have deployed our ClearSign Core TM technology through the retrofit or replacement of existing burners.

As noted above, retrofits often involve engineering around an existing burner architecture that can complicate the installation.

By developing our ClearSign Core TM technology into a replacement product, we have been able to standardize our designs and simplify supply-chain demands.

In addition, we have enabled collaboration with other commercial equipment suppliers with the intent to incorporate our ClearSign Core TM technology into their standard product lines.

To date, we have deployed our ClearSign Core TM technology through the replacement of existing burners.

As noted above, retrofits often involve engineering around an existing heater architecture that can complicate the installation.

By developing our ClearSign Core TM technology into a replacement product, we have been able to standardize our designs and simplify supply chain

In addition, we have collaborated with heater OEM’s for the purpose of incorporating our ClearSign Core TM technology into their typical product lines.

We believe that this further development of our products has greatly increased our ability to collaborate with partners to extend our potential market reach and the resources we make available to our prospective customers.

Process Heaters in the Oil Refining, Petrochemical and Gas Processing Industries

To date, we have retrofitted six process heaters with our new ClearSign Core TM process burners for refineries and fuel distributors, some of which are owned by global supermajor companies and Fortune 500 companies.

Sites include four locations in California and one in Europe.

The ClearSign Core TM design provides a more simplified, pre-engineered and standardized direct burner replacement for traditional refinery process heaters that we believe can be mass produced and reduce the need for the customized engineering associated with typical retrofits.

The ClearSign Core TM design (including the boiler burner version) is our most developed burner product.

To date, we have retrofitted fourteen process heaters with our new ClearSign Core TM process burners for refineries and fuel distributors, some of which are owned by global supermajor companies and Fortune 500 companies.

Sites include five locations in California and one in Europe.

The ClearSign Core TM design provides a more simplified and standardized direct burner replacement for traditional midstream and refinery process heaters.

We believe that significant portions of these burners have the potential to be mass produced and provide the potential to reduce the need for the customized engineering associated with typical retrofits.

The ClearSign Core TM design (including our “M-Series” burner line) is our most developed burner product.

It operates essentially in the same way as a standard burner, including fitting into a heater and integrating with existing control systems.

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At this time, we have a collaboration agreement in place with Zeeco Inc., one of the world’s largest combustion equipment manufacturers (“Zeeco”).

The selling and marketing of our process burners pursuant to this agreement, however, is contingent upon terms still under negotiation.

In 2021, we received our first international purchase order for a ClearSign Core refining process heater from a global supermajor refining company.

This agreement affords ClearSign the ability to use Zeeco’s industrial scale test facility, subcontract manufacturing of burners, coordinate marketing initiatives and seamlessly communicate with sales resources.

This agreement confirms the cooperation between the two companies, and allows for various forms of collaboration, and the ongoing progression of our relationship as both parties deem mutually beneficial.

In 2021, we received our first international purchase order for a ClearSign Core TM refining process heater from a global supermajor refining company.

This marked the second order we received from a global supermajor company.

This international order was installed in 2021 and successfully placed it into full operation by the customer in January 2022.

This international order was installed in 2021 and was successfully placed it into full operation by the customer in January 2022.

In addition, we fulfilled a multi-burner order for a Fortune 500 infrastructure company that continues to consistently meet all performance requirements including compliance with the California site’s air quality permit.

The process burner installed at this site was used by SCAQMD to set new BACT guidelines (see discussion above under the “Our Industry” section).

We also received a purchase order in 2022 from a California refinery for our ClearSign Core TM process burners, amounting to twenty burners.

Due to project delays, which were outside of our control, the process burners for this order were shipped to the jobsite during the third quarter of 2024 but the installation into the customer’s heater is now expected to occur during the third quarter of 2025.

The process burner installed at this site was used by SCAQMD to set new BACT guidelines (see discussion above under the “Our Industry” section above).

We also received a purchase order in 2022 from a California refinery for our ClearSign Core TM process burners, amounting to twenty burners for two separate heaters.

Due to project delays, which were outside of our control, the process burners for this order were shipped to the jobsite during the third quarter of 2024 and were installed during the third quarter of 2025.

The burners for this order remain operational and have met applicable emissions requirements;

however, as of the date of this report, we are in the process of modifying these burners to complete their contractual performance requirements at high firing rates.

On May 18, 2023, we received an order for thirteen process burners from an existing California refinery customer.

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The process burners installed in both heaters have passed the customer’s NOx emissions permit level, which were validated by third-party inspectors.

In 2023, we received a purchase order from a heater manufacturer to install a modified ClearSign Core TM boiler burner into a horizontally fired process heater.

On November 27, 2024 we received an order from Birwelco USA Inc.

(a BIH Group company) (“Birwelco”) for twenty-six burners to be installed in a Gulf Coast facility operated by a Fortune 500 global chemical company.

These burners have been delivered to the customer and, as of the date of this report, their installation is anticipated to occur on or around the middle of 2026.

In 2023, we received a purchase order from a heater manufacturer to install a forced air ClearSign Core TM burner into a horizontally fired process heater.

The end customer was a chemical company located in Texas.

This project was a significant achievement for us, since it gave us the ability to demonstrate a new product offering.

Since that first order in 2023, we have received three more orders for this same type of application.

This project was a significant achievement for us, since it gave us the ability to demonstrate a new product offering, which we have branded the “M-Series” (including the M-1 and M-25 burners).

Since that first order in 2023, we have received five more orders for this same type of application and several requests from customers seeking bids for future project work.

We believe these orders are representative of an underserved and growing market opportunity in low emissions burners for horizontally fired process heaters.

Two of these orders are in the state of Texas, and are believed to be a response to anticipated changes to Texas air emissions regulations, which we expect will ultimately lead to additional demand for our technology.

As we seek to expand the markets into which we can sell our products, we plan to continue extending the range of ClearSign Core TM process burners to enable the replacement of other burner shapes and configurations, as well as for use in alternate process applications.

Two of these orders are in the state of Texas, and are believed to be associated with anticipated changes to Texas air emissions regulations, which we expect will ultimately lead to additional demand for our technology.

Due to the growing demand from our heater OEM customers, we developed a mid-range “M-Series” burner, the M-25 burner, to serve markets where the most stringent NOx regulations are not required, but there is still a demand for improved burner technology.

To date, we have received two orders for this type of burner and issued several proposals in response to customer bid requests.

We believe that this burner provides us with a significant opportunity to sell our products into a large and growing midstream gas processing and transportation industry.

As we seek to expand the markets into which we can sell our products, we plan to continue extending the range of ClearSign Core TM process burners to enable the replacement of other burner types and configurations, as well as for use in alternate process applications.

Hydrogen Process Burners

We are currently in the research and development phase to design a one-hundred percent hydrogen capable ClearSign Core TM process burner.

We have recently completed the technical research and development phase of the one-hundred percent hydrogen capable ClearSign Core TM process burner project.

The goal of this project is to develop an ultra-low NOx hydrogen burner, which we believe will enable the adoption of hydrogen fuel for industrial heating, leading to reductions in the industrial emissions of both carbon dioxide and nitrogen oxides.

Current burners and previous efforts to decarbonize industrial combustion processes through the utilization of hydrogen fuel are inhibited by the lack of industrial hydrogen burners capable of burning pure hydrogen while controlling emissions of NOx emissions to the most stringent levels required in the industry.

We have received two grants from the Department of Energy (“DOE”) to fund the development of this technology.

In total, the DOE awards approximate $1.9 million in the aggregate, with a target end date occurring in 2025.

We have received two grants from the DOE to fund the development of this technology.

In total, the DOE awards approximate $1.9 million in the aggregate, with a target end date for the project occurring in the first quarter of 2026.

See “Note 13 – Government Assistance” for further details about these monies.

As of the date of this report, we have proven that a modified version of our ClearSign Core TM process burner can burn “pure” hydrogen fuel while maintaining ultra-low NOx emissions by firing this burner in an industrial scale test facility.

We believe that the findings from this research and development project have proven to be a valuable addition to the advancement of our technology, affording us the ability to solve highly complex problems related, but not limited to, complex multiple fuel feedstocks.

Industrial Commercial Boilers

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In our target markets, boilers exist in two different industry-standard forms:

water tube, which tend to be larger and in which the water or steam

flows through a series of tubes that surround the space in which the flame forms;

water tube, which tend to be larger and in which the water or steam flows through a series of tubes that surround the space in which the flame forms;

or fire tube in which the flame is formed inside a large tube that passes through the outer vessel holding the water.

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For fire tube products, we have developed our own patent protected burner replacement product that is similar in concept to our ClearSign Core TM burners for process heaters.

These boiler burners have achieved performance levels meeting the most stringent new California NOx regulations, in a typical commercial fire tube boiler produced by one of the industry’s largest suppliers in the U.S.

These boiler burners have achieved performance levels meeting the most stringent California NOx-related regulations in a typical commercial fire tube boiler produced by one of the industry’s largest suppliers in the U.S.

For instance, through our collaboration agreement in place with California Boiler to sell, deliver, install and service fire tube boiler burners in the U.S., we were able access larger sizes of fire tube boilers in order to verify the function of a range of fire tube boiler burners.

In 2023, we received two purchase orders for our ClearSign Core boiler burner technology.

In 2023, we received two purchase orders for our ClearSign Core TM boiler burner technology.

Both boiler burner purchase orders were sold as a package with our collaborative partner, California Boiler, and its subsidiary, Rogue Combustion, into the San Joaquin Valley Air Pollution Control District of California.

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In 2024, we received three additional orders from Rogue Combustion with one of these three orders accompanied by a letter of intent for three follow-on orders.

During 2025, our partner California Boiler, and its subsidiary Rogue Combustion submitted several proposals to customers seeking bids for our boiler burner technology and new boilers containing our boiler burner technology, but no purchase commitments were received during 2025.

Wellhead Enclosed Flares

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Our collaboration agreement with the field engineering and servicing company California Boiler includes flare sales and installation.

To date, we have four flare units installed and operating in California resulting from this California Boiler collaboration agreement.

To date, we have four flare units installed and operating in California resulting from our collaboration with California Boiler.

During 2025, we received purchase orders from an existing California energy company for the major components of two retrofit flare systems.

These orders varied in scope and value and included characteristics such as burner fabrication, stack fabrication, controls equipment sourcing, Computational Fluid Dynamic (“CFD”) study, engineering study and engineering services.

We have continued to submit bids to this customer for future projects.

We have also submitted a bid for a thermal oxidizer project, which utilizes a similar technology to our flare products, in Colorado where the customer sought our emissions control technology to increase their total processing output without exceeding their current applicable permitted emissions quota.

We believe that the

increase in flare and thermal oxidizer orders during 2025 and related bids further advances our prediction that local regulators are targeting NOx flare and thermal oxidizer emissions.

OTSGs for the Enhanced Oil Recovery Industry

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Field data reported by our customers indicates significant efficiency improvements resulting from the installation of the ClearSign technology.

We believe our new standardized boiler burner range of products is also well suited to this application.

We believe our new standardized “M-Series" burner range of products is also well-suited to this application.

Sensing Products

We are currently engaged with a prominent refining customer as a first adopter to install our flame sensors on burners in one of their heaters facilitating our first field demonstration.

Although we have not yet completed the product launch of our sensing products and subsequent commercialization thereof, we have obtained clear and consistent customer feedback guiding its first application.

We are currently engaged with two refining customers to install our flame sensors on burners in their heaters, which will facilitate our first field demonstrations with certain first adopter customers.

Although we have not yet completed commercialization of these products, we have obtained clear and consistent customer feedback guiding this product application.

The target market for this technology is potentially every burner with a pilot on which flame sensors are deployed, providing a global and very high-volume opportunity.

This market is not limited by emissions mandates or the type or manufacturer of the burners.

The product has value for retrofit applications, where it is applied to existing burners, and for new burners, where it can be installed in burners by OEMs.

The product has value for retrofit applications, where it is applied to existing burners, and for new burners, where it can be installed in burners by other burner OEMs.

We are assessing the possibility of manufacturing the sensing products ourselves as well as partnering with one or more established OEM suppliers.

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We have received notable interest in this product from a major global customer giving us the confidence that there is a potential market for this technology, which is therefore worthy of future investment.

This sensor product is in the very early stages of development and would be deployed in a highly regulated environment requiring a thorough product development process.

The interest we have received to date, however, suggests that this could potentially be a significant future business opportunity for ClearSign.

As a result, we believe that the interest we have received to date suggests that this could potentially be a significant future business opportunity for us.

This sensor product, however, is in the very early stages of development and would be deployed in a highly regulated environment requiring a thorough product development process.

We entered into a collaboration agreement with Narion, which allows us to leverage their technical expertise in this area to further develop our technology for this potential market.

Our Target Markets

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We are targeting the following segments of the combustion market for adoption of our ClearSign Core TM technology:

● institutional, commercial and industrial boilers;

● refining, energy infrastructure and petrochemical process heaters;

● enclosed flares and thermal oxidizers;

● midstream gas processing and transportation;

● enhanced oil recovery steam generators;

● institutional, commercial and industrial boilers.

In each of these segments, we are marketing solutions that include our ClearSign Core TM technology which we believe could simultaneously improve productivity, operational efficiency and pollution control.

Our target markets are greatly affected by air emission regulations and economic conditions.

Accordingly, we prioritize our activities in target market segments geographically based on the needs of the local industries and the current and anticipated future requirements imposed by local environmental regulations.

Details regarding the localized effect of environmental regulations in the United States are described in the section of this report titled “Our Industry.” In general, our immediate regional opportunities are in the West and Gulf Coasts of the United States.

Accordingly, we prioritize our activities in target market segments geographically based on the needs of the local industries and the current and anticipated future

requirements imposed by local environmental regulations.

See the sections titled “Our Industry” and “Government Regulations” in this report for more details regarding the localized effect of environmental regulations in the United States.

In general, our immediate regional opportunities are in the West and Gulf Coasts of the United States.

Competition and Barriers to Entry

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These suppliers possess resources that are substantially greater than ours.

Worldwide, suppliers of burners and air pollution control equipment include but are not limited to companies such as Callidus, Eclipse and Maxon (all three are subsidiaries of Honeywell), John Zink Hamworthy Combustion (a subsidiary of Koch Industries and including Coen), General Electric, Haldor Topsøe, Hitachi, Linde, Zeeco, Fives Group, Cleaver Brooks, Power Flame (a subsidiary of Aztec Inc.), and others.

These companies provide systems that include low and ultra-low NOx burners, selective and non-selective catalytic reduction systems, and other pollution control technologies.

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As a result of the relatively slow pace of developing and adopting innovation, we believe the technology and products currently being offered by our large competitors have become commoditized with differentiation between suppliers most often based on price.

These industry characteristics provide both an opportunity and a barrier to more nimble, disruptive companies.

We believe that these industry characteristics provide both an opportunity and a barrier to more nimble, disruptive companies.

From a customer’s perspective, installation of legacy air pollution control technologies is viewed as a method of avoiding fines, as a cost of doing business, and as a means to operate within current and anticipated future regulatory requirements.

Unlike most other kinds of capital equipment that provide an economic return through enhanced productivity or efficiency, we believe customers of traditional emissions control equipment do not expect any positive return on emissions control investments other than the ability to continue to operate or avoid fines.

We believe the ClearSign Core TM suite of products are further differentiated from its competitors because they give prospective customers the opportunity to greatly reduce capital investment and, in certain cases, realize a return on investment through increased efficiency and/or increased productivity.

We believe that the ClearSign Core TM suite of products are further differentiated from its competitors because they give prospective customers the opportunity to greatly reduce capital investment and, in certain cases, realize a return on investment through increased efficiency and/or increased productivity.

As indicated above, we are seeking to develop our business in the combustion and emissions control market and to establish ourselves in a highly competitive industry among companies that have substantial financial resources, a well-developed infrastructure and established products.

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We are a small company with limited financial resources and do not have the infrastructure to meet the requirements of our sophisticated target global customers without significant investment and increase in operational costs.

Although we have highly skilled and experienced employees, we do not have the manpower to provide comprehensive service and customer support ourselves.

Further, although we have highly skilled and experienced employees, we do not have the manpower to provide comprehensive service and customer support ourselves.

We believe that it is in the best interests of the Company and our stockholders to develop our business utilizing an “asset light” model.

Accordingly, we seek to collaborate with strategic partners to the extent possible to sell our products and maximize the profitability of those sales.

Accordingly, we continuously seek to collaborate with strategic partners to the extent possible to sell our products and maximize the profitability of those sales.

We believe that our technology is our main strength, which has been developed to provide a standard set of “core” components that can be incorporated into any generic OEM burner body.

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We believe that our strengths also include the market opportunity potentially created by new and anticipated environmental emissions control regulations.

These regulations will potentially require combustion performance that either exceeds the technology available from the incumbent equipment manufacturers or requires retrofitting existing equipment with a post-combustion clean up apparatus.

Installing clean-up apparatus is very expensive especially for small to mid-sized heaters.

We believe that the incumbent burner OEM product development approaches are, and will continue to be, incremental in nature, and are unlikely to pose a significant threat to the value provided by ClearSign Core technology in the foreseeable future.

These regulations will potentially require combustion performance that either exceeds the technology available from the incumbent equipment manufacturers or require retrofitting existing equipment with a post-combustion clean up apparatus, which is very expensive, especially for small to mid-sized heaters.

We believe that the incumbent burner OEM product development approaches are, and will continue to be, incremental in nature, and are unlikely to pose a significant threat to the value provided by our ClearSign Core TM technology in the foreseeable future.

Manufacturing Footprint and Product Quality Strategy

Our business has been, and continues to be, developed with the goal of combining our technology with the infrastructure and resources of major OEM equipment manufacturers.

Through such collaborative arrangements, OEM burner manufacturers can reap the benefits of adding truly differentiated and unique product lines to their offerings and ClearSign can overcome the barrier to market of needing to build capital and operating expense-intensive infrastructure and hiring a large specialist staff.

We also believe that having orders fulfilled by a well-known and trusted supplier will reduce the risk, as perceived by prospective customers, of dealing with a small company.

We expect that developing strategically chosen collaborative partnerships will result in supplying ClearSign Core TM technology to major global customers in large quantities together with the attendant engineering, quality control, customer support and project management services required by these sophisticated customers.

We also believe that our collaborative partnerships will enable our OEM partners to offer a unique product in the marketplace and provide both parties with a potentially significant commercial opportunity.

Forming such alliances is expected to dramatically accelerate the global sales and market adoption of our technology.

Through such business relationships, OEM burner manufacturers can reap the benefits of adding truly differentiated and unique product lines to their offerings and we can overcome the barrier to market of needing to build capital and operating expense-intensive infrastructure and hiring a large specialist staff.

We also believe that having orders fulfilled by well-known and trusted suppliers will reduce the risk, as perceived by prospective customers, of dealing with a smaller company.

We expect that developing strategically chosen collaborative business arrangements will result in our ability to supply ClearSign Core TM technology to major global customers in large quantities together with the attendant engineering, quality control, customer support and project management services required by these sophisticated customers.

We also believe that our collaborative business arrangements will enable our OEM relationships to offer a unique product in the marketplace and provide both parties with a potentially significant commercial opportunity.

Forming such collaborations and relationships is expected to dramatically accelerate the global sales and market adoption of our technology.

As announced in June 2019, we already have an agreement in place with Zeeco, who is one of the world’s largest burner manufacturers, to globally manufacture ClearSign Core TM process burners.

In December 2024, Zeeco and ClearSign announced the launch of a co-branded ClearSign Core process burner product line.

We believe that this announcement marked the next stage of

evolution in our relationship with Zeeco, where we will work together to market and sell ClearSign Core TM technology.

In December 2024, Zeeco and us announced the launch of a co-branded ClearSign Core TM process burner product line.

We believe that this announcement marked the next stage of evolution in our relationship with Zeeco, where we will work together to market and sell ClearSign Core TM technology.

We are continuing to negotiate this next phase of our relationship, but we view this announcement as a commitment to solidify our shared marketing and sales efforts of ClearSign Core™ technology going forward.

In addition, we have a collaborative agreement with California Boiler to sell and produce both fire tube boiler burner and flare products.

California Boiler created a wholly owned subsidiary Rogue Combustion for the purpose of marketing boiler burner systems solution using our ClearSign Core TM technology, which are branded as Near Zero NOx (“NZN”) and Sub 5ppm NOx (“S5”) and Sub 9ppm NOx (“S9”) solutions.

California Boiler created a wholly owned subsidiary Rogue Combustion for the purpose of marketing boiler burner systems solution using our ClearSign Core TM technology, which are branded as Near Zero NOx (“NZN”), Sub 5ppm NOx (“S5”) and Sub 9ppm NOx (“S9”) solutions.

Typically, boiler burner customers rely on integrated service providers to design, install and service boiler burner systems.

Our collaborative relationship with California Boiler and Rogue Combustion aligns with our “asset light” philosophy by providing us with a low-cost path to market, by limiting human capital investment in maintenance and installation technicians.

Further, our collaborative relationship with California Boiler and Rogue Combustion aligns with our “asset light” philosophy by providing us with a low-cost path to market, by limiting human capital investment in maintenance and installation technicians.

Sales Channel and Marketing Strategy

In addition to targeting OEM manufacturers and service providers to augment our manufacturing footprint and on-time service capabilities, we target sales and marketing efforts at OEM heater companies and engineering companies supporting our refining, petrochemical and energy infrastructure customers.

By focusing on this sales channel, we believe we can quickly gain repeat sales given these customers act as a conduit to multiple end users, which also allows us to maximize the reach of our limited selling and marketing resources.

In 2024, as a result of adopting such go-to-market strategy, we received multiple orders originating from a single heater OEM.

By focusing on this sales channel, we believe we can quickly gain repeat sales given that these customers act as a conduit to multiple end users, which also allows us to maximize the reach of our limited selling and marketing resources.

As an example, as a result of adopting this go-to-market strategy, we received multiple orders originating from a single heater OEM.

We value and nurture our relationships with end users, and we view this sales channel as a critical path to overall market acceptance, since end users ultimately own and operate our equipment.

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We further believe that fostering these relationships will help us drive demand for our products downstream to OEM heater manufacturers and engineering service companies.

We expect that these end users, as first adopters of our technology, will also play a vital role in future sales efforts by providing references to prospective customers, as, based on our experience, prospective customers frequently request a reference from an existing customer.

We expect that these end users, as first adopters of our technology, will also play a vital role in future sales efforts by providing references to prospective customers, given that, based on our experience, prospective customers frequently request a reference from an existing customer.

Another aspect of our marketing strategy relies on obtaining reputable third-party validation of our technology by demonstrating that our burners can meet or exceed the operational characteristics we set out to achieve.

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In addition, we participated in a study executed by the California Gas Emerging Technologies (“GET”) program to test and quantify the emissions improvements and efficiency gains of our ultra-low NOx boiler burner as compared to a conventional (or baseline) ultra-low NOx burner.

ICF a global advisory and technology service company, released its independent report on October 2, 2024, detailing the results of this study.

ICF International, a global advisory and technology service company, released its independent report on October 2, 2024, detailing the results of this study.

In summary, our technology reported fuel savings at 3.3% when operating at sub-2.5 ppm NOx and 4.7% at sub-9 ppm NOx;

electricity savings reported 7% at sub-2.5 ppm NOx and 25% at sub-9 ppm NOx.

and electricity savings of 7% at sub-2.5 ppm NOx and 25% at sub-9 ppm NOx.

We believe these third-party reviews of our technology play a critical role in proving the efficacy of our technologies and dispelling industry skepticism.

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Our operating activities are substantially all located within the United States, and our customers located in the United States accounted for 100% of revenues in the fiscal years ended December 31, 2025 and 2024.

Our two California refinery customers accounted for 86% and 87% of our annual revenue for the years ended December 31, 2024 and 2023, respectively.

Our two California refinery customers accounted for 15% and 86% of our annual revenue for the years ended December 31, 2025 and 2024, respectively, with Birwelco accounting for 66% and 0% of our annual revenue for years ended December 31, 2025 and 2024, respectively.

No other customer represented greater than ten percent of annual revenues for the years ended December 31, 2025 and 2024.

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This model allows us to maximize the value of our limited resources while minimizing capital investment.

Our subcontractor, for the process burner product line, is intentionally single sourced through a collaborative agreement with a well-known and established industry leader, Zeeco.

Our subcontractor for the process burner product line is intentionally single sourced through a collaborative agreement with a well-known and established industry leader,

Zeeco, as described above.

Our boiler burner product line is not dependent upon a single-sourced subcontractor.

While we continuously assess, for any improvements in productivity and supply chain efficiency, there can be no assurance that our subcontractors will not experience supply interruptions, production capacity constraints or working capital limitations, which could adversely affect our business.

While we continuously assess possible improvements in productivity and supply chain efficiency, there can be no assurance that our subcontractors will not experience supply interruptions, production capacity constraints or working capital limitations, which could adversely affect our business.

Raw steel and fabricated steel parts are a major component of our product cost, purchases of which are subject to the needs and specifications of our customers or subcontractors.

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We will continue to assess research and development opportunities to develop new product offerings where appropriate based on customer feedback and market trends.

We are currently continuing to develop our flame sensing and hydrogen burner technology, which is discussed in detail under the “ClearSign Core™ Technology Product Applications” section above in addition to the expansion of our burner technologies, and potentially other technologies aligned with our expertise and business focus, into adjacent customer applications and market verticals.

We are currently continuing to develop our flame sensing and hydrogen burner technology, which is discussed in detail under the “ClearSign Core™ Technology Product Applications” section above in addition to the expansion of our burner technologies, as well as potentially other technologies aligned with our expertise and business focus, into adjacent customer applications and market verticals.

Intellectual Property Protection

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We maintain an active review process to monitor for new inventions across the globe that threaten our intellectual property protection.

Our active patents range in age of duration from 8 years to 18 years, with the majority approximating 11 years of life remaining.

We cannot predict when our patent applications may result in issued patents, if at all.

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In addition, field implementation of our technologies requires permits from various local, state and federal agencies that regulate mechanical and electrical infrastructure and fire and air pollution control.

Federal and state regulatory authorities have pursued regulatory and policy initiatives impacting air emissions in the United States from a variety of sources, but such initiatives continue to be controversial and subject to frequent changes and revisions depending on legal and political developments.

At this time, we believe that the current U.S.

administration does not support “green initiatives.” For example, in February 2026, the EPA finalized its rescission of the 2009 greenhouse gas endangerment finding under the Clean Air Act, which determined that certain greenhouse gas emissions qualify as air pollution that endangers human health or the environment.

The final rule rescinding the 2009 greenhouse gas endangerment finding is expected to be challenged in the U.S.

Court of Appeals for the District of Columbia Circuit and ultimately appealed to the U.S.

Supreme Court for final adjudication, which could take several years.

However, we believe that this final rule will have no impact on future regulations and rules regarding NOx emissions promulgated under the Clean Air Act.

We are currently not aware of any current or proposed federal, state or local environmental compliance regulations that would have a material detrimental effect on our business objectives or operations, including the recent rescission of the 2009 greenhouse gas endangerment finding by the EPA.

environmental regulation that supports the adoption of our technology originates from the Clean Air Act, as well as state laws and regulations impacting air emissions, which provides a framework for protecting and improving air quality and controlling sources of certain emissions, including NOx emissions.

The Clean Air Act had several subsequent amendments specifically targeting NOx emissions, including the 1990 amendments to the Clean Air Act, or the Acid Rain Program, which contained requirements to reduce NOx emissions through the use of available combustion controls, which remains unchanged after the rescission of the 2009 greenhouse gas endangerment finding.

Therefore, by itself, the rescission of the 2009 greenhouse gas endangerment finding has no impact on us, our business objectives or operations.

While the current political environment may not be conducive for strengthening emissions controls at a national level, we believe global mega trends induced by social and political sentiment, and local and state regulatory requirements have laid the groundwork for continued support and adoption of our technology.

In addition, we do not anticipate any major capital expenditures to be required in order for our technology to comply with any environmental protection regulations.

We believe that we offer major advances in emissions reductions and efficiency improvements.

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Ultimately, it may be possible for our technology to achieve BARCT and/or MACT designation.

We believe that the availability of our technology alone may accelerate the government’s willingness to adopt more stringent environmental regulations.

Further, we believe efficiency improvements, combined with the elimination of flame impingement, could generate market demand regardless of the existing regulatory framework because the potential efficiency, productivity and savings gains from our products could result in the adoption of our technology.

At this time, we believe that the current U.S.

administration does not support “green initiatives.” Nevertheless, we are not aware of any current or proposed federal, state or local environmental compliance regulations that would have a material detrimental effect on our business objectives or operations.

environmental regulation that supports the adoption of our technology originates from the Clean Air Act, which had several subsequent amendments specifically targeting NOx emissions, including the 1990 amendments to the Clean Air Act, or the Acid Rain Program, which contained requirements to reduce NOx emissions through the use of available combustion controls.

In addition, we do not anticipate any major expenditures to be required in order for our technology to comply with any environmental protection statutes.

We believe that the availability of our technology alone may accelerate the regulatory authorities’ willingness to adopt more stringent environmental regulations.

Further, we believe that efficiency improvements, combined with the elimination of flame impingement, could generate market demand regardless of the existing regulatory framework because the potential efficiency, productivity and savings gains from our products could result in the adoption of our technology.

Human Capital

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Our employees are not covered by collective bargaining agreements, and we believe our relationship with our employees is good.

Corporate History

Corporate Information

We were incorporated in the State of Washington on January 23, 2008.

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The address of our corporate headquarters is 8023 East 63rd Place, Suite 101, Tulsa, Oklahoma 74133 and our telephone number is (918) 500-7312.

Our website can be accessed at www.clearsign.com.

The information contained on our website is not a part of this report.

We currently operate in the United States.

We have a wholly-owned subsidiary incorporated Hong Kong, China, but we are not currently operating in Hong Kong, China, because such entity is in a dormant status, which status became effective on March 12, 2025.

On July 28, 2017, the Company incorporated a subsidiary, ClearSign Asia Limited, in Hong Kong to represent the Company’s business and technological interests throughout Asia.

Through ClearSign Asia Limited, the Company has established a wholly foreign owned enterprise in China named ClearSign Combustion (Beijing) Environmental Technologies Co., LTD.

On August 22, 2024, the Company’s board of directors (the “Board”) approved to file for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations.

A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years.

The Company can resume its China operations at any time during those three years with minimal cost impact.

The effective date of our dormancy filing was March 12, 2025.

The name “ClearSign,” the “ClearSign Technologies Corporation” logo, and other registered or common law trademarks or service marks of ClearSign Technologies Corporation appearing in this report are the property of ClearSign Technologies Corporation.

Other trademarks and tradenames referred to in this report, if any, are the property of their respective owners.

Solely for convenience, trade names, trademarks, and service marks referred to in this report may appear without the ® or TM symbols.

Such references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or the rights of the applicable licensor to such trade names, trademarks, and service marks.

Available Information

Our website address is www.clearsign.com.

The information in our website is not incorporated by reference into this report.

Through a link on the “Investors” section of our website, we make available our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and any amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act, as soon as reasonably practicable after they are filed with, or furnished to, the Securities and Exchange Commission (the “SEC”).

You can also read any materials submitted electronically by us to the SEC on its website (www.sec.gov), which contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC, including us.

Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-K

Item 1. Business