The counter-flow burner comprises a combustion chamber (5) in which a fuel gas (B) and an oxidizing agent (O) are fed from opposite sides, three planar substrates (1, 2, 3) connected one above the other with each other, and structures. The middle substrate comprises the combustion chamber into which channels (4) lead from opposite directions, where openings of the channels in the combustion chamber have a distance of less than 3 mm. A size of the openings of the channels into the combustion chamber is 0.005-0.08 mm 2>. The channels radially lead into the combustion chamber. The counter-flow burner comprises a combustion chamber (5) in which a fuel gas (B) and an oxidizing agent (O) are fed from opposite sides, three planar substrates (1, 2, 3) connected one above the other, and structures. The middle substrate comprises the combustion chamber into which channels (4) lead from opposite directions, where openings of the channels in the combustion chamber have a distance of less than 3 mm. A size of the openings of the channels into the combustion chamber is 0.005-0.08 mm 2>. The channels radially lead into the combustion chamber. The structures, through which gases are fed to the counter-flow burners and through which exhaust gases leave the counter-flow burner, are preheated. Independent claims are included for: (1) a flame ionization detector; and (2) a method for analyzing a sample gas.