Note 1 - General	9 Months Ended
Sep. 30, 2023
Notes to Financial Statements
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block]	1. General Organization Fuel Tech, Inc. and subsidiaries ("Fuel Tech", the "Company", "we", "us" or "our") develops and provides proprietary technologies for air pollution control, process optimization, water treatment, and advanced engineering services. These technologies enable customers to operate in a cost-effective and environmentally sustainable manner. The Company’s nitrogen oxide (NOx) reduction technologies reduce nitrogen oxide emissions from boilers, furnaces, and other stationary combustion sources. To reduce NOx emissions, our technologies utilize advanced combustion modification techniques and post-combustion NOx control approaches including non-catalytic, catalytic, and combined systems. The Company also provides solutions for the mitigation of particulate matter, including particulate control with electrostatic precipitator products and services, and using flue gas conditioning systems which modify the ash properties of particulate for improved collection efficiency. The Company’s FUEL CHEM® technology improves the efficiency, reliability, fuel flexibility, boiler heat rate, and environmental status of combustion units by controlling slagging, fouling, corrosion, and opacity. Water treatment technologies include DGI® Dissolved Gas Infusion Systems which utilize a patented gas-infusing saturator vessel and a patent-pending channel injector to deliver supersaturated oxygen-water solutions and potentially other gas-liquid combinations to target process applications or environmental issues within the municipal and industrial water sectors. The infusion process has a variety of potential applications in the water and wastewater treatment sector, including aquaculture, agriculture/horticulture, pulp & paper, tanneries, landfill leachate, irrigation, treatment of natural waters, wastewater odor management as well as supplying oxygen or other gases for biochemical reactions and pH adjustment. Many of Fuel Tech’s products and services rely heavily on the Company’s computational fluid dynamics modeling capabilities, which are enhanced by internally developed, high-end visualization software. Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X of the Exchange Act. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, the financial statements reflect all adjustments (consisting of normal recurring accruals) considered necessary for the fair statement of Fuel Tech's financial position, cash flows, and results of operations for the periods presented. All significant intercompany transactions and balances have been eliminated. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the full year ending December 31, 2023. For further information, refer to the audited consolidated financial statements and footnotes thereto included in Fuel Tech’s Annual Report on Form 10-K for the year ended December 31, 2022 as filed with the Securities and Exchange Commission. Global Health and Geopolitical Events Management cannot predict the full impact of the COVID-19 pandemic and geopolitical events on the Company’s sales and marketing channels and supply chain, and as a result, the ultimate extent of the effects on the Company are highly uncertain and will depend on future developments. The Company continues to monitor the potential impacts on the business.

Note 1 - General

9 Months Ended

Sep. 30, 2023

Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block]

1. General

Organization

Fuel Tech, Inc. and subsidiaries ("Fuel Tech", the "Company", "we", "us" or "our") develops and provides proprietary technologies for air pollution control, process optimization, water treatment, and advanced engineering services. These technologies enable customers to operate in a cost-effective and environmentally sustainable manner.

The Company’s nitrogen oxide (NOx) reduction technologies reduce nitrogen oxide emissions from boilers, furnaces, and other stationary combustion sources. To reduce NOx emissions, our technologies utilize advanced combustion modification techniques and post-combustion NOx control approaches including non-catalytic, catalytic, and combined systems. The Company also provides solutions for the mitigation of particulate matter, including particulate control with electrostatic precipitator products and services, and using flue gas conditioning systems which modify the ash properties of particulate for improved collection efficiency. The Company’s FUEL CHEM® technology improves the efficiency, reliability, fuel flexibility, boiler heat rate, and environmental status of combustion units by controlling slagging, fouling, corrosion, and opacity. Water treatment technologies include DGI® Dissolved Gas Infusion Systems which utilize a patented gas-infusing saturator vessel and a patent-pending channel injector to deliver supersaturated oxygen-water solutions and potentially other gas-liquid combinations to target process applications or environmental issues within the municipal and industrial water sectors. The infusion process has a variety of potential applications in the water and wastewater treatment sector, including aquaculture, agriculture/horticulture, pulp & paper, tanneries, landfill leachate, irrigation, treatment of natural waters, wastewater odor management as well as supplying oxygen or other gases for biochemical reactions and pH adjustment.

Many of Fuel Tech’s products and services rely heavily on the Company’s computational fluid dynamics modeling capabilities, which are enhanced by internally developed, high-end visualization software.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X of the Exchange Act. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, the financial statements reflect all adjustments (consisting of normal recurring accruals) considered necessary for the fair statement of Fuel Tech's financial position, cash flows, and results of operations for the periods presented. All significant intercompany transactions and balances have been eliminated. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the full year ending December 31, 2023. For further information, refer to the audited consolidated financial statements and footnotes thereto included in Fuel Tech’s Annual Report on Form 10-K for the year ended December 31, 2022 as filed with the Securities and Exchange Commission.

Global Health and Geopolitical Events

Management cannot predict the full impact of the COVID-19 pandemic and geopolitical events on the Company’s sales and marketing channels and supply chain, and as a result, the ultimate extent of the effects on the Company are highly uncertain and will depend on future developments. The Company continues to monitor the potential impacts on the business.