A universal portable breath content analyzer comprising: a sealed housing having an outer wall, a first end face wall and a second end face wall located opposite to the first end face, the sealed housing having an interior defined by the outer wall, the first end face, and the second end face; a first electrode that passes into the interior of the sealed housing through one of the end faces; a voltage supply source connected to the first electrode for applying a voltage to the first electrode; a counter electrode for interaction with the first electrode and for generating a discharge in the interior of the sealed housing when a voltage sufficient for generating a discharge between the first electrode and the second electrode is applied to the first electrode; a mouthpiece for taking a sample of an exhaled air exhaled by a patient and for supplying the exhaled air into the interior of the sealed housing; a flow control valve installed in the mouthpiece for keeping the mouthpiece open or closed; an air evacuation tube inserted into the interior of the sealed housing; a vacuum pump with a driver connected to the air evacuation tube; a shut-off valve installed in the air evacuation tube between the interior of the sealed housing and the vacuum pump; a pressure sensor located inside the interior of the sealed housing for measuring pressure in said interior; an opening in the outer wall; a transparent plate installed in the opening; a set of replaceable optical filter/waveband sensor assemblies removably installable onto the transparent plate, each replaceable optical filter/waveband filter assembly comprising a waveband filter for passing light of the discharge having a predetermined waveband and a sensor capable of converting optical signals of the discharge into electrical signals; and central processing unit, which is connected to the flow control valve, the shut-off valve, the voltage supply source, the driver of the vacuum pump, and the pressure sensor of each replaceable optical filter/waveband filter assembly for controlling operations of aforementioned devices depending on the pressure measured by the pressure sensor, wherein the housing is a cylindrical body, at least a part of the outer wall is transparent, and the counter electrode is a semi-cylindrical mirror that is located outside the outer housing and encompasses said at least a part of the outer wall, which is transparent. a sealed housing having an outer wall, a first end face wall and a second end face wall located opposite to the first end face, the sealed housing having an interior defined by the outer wall, the first end face, and the second end face; a first electrode that passes into the interior of the sealed housing through one of the end faces; a voltage supply source connected to the first electrode for applying a voltage to the first electrode; a counter electrode for interaction with the first electrode and for generating a discharge in the interior of the sealed housing when a voltage sufficient for generating a discharge between the first electrode and the second electrode is applied to the first electrode; a mouthpiece for taking a sample of an exhaled air exhaled by a patient and for supplying the exhaled air into the interior of the sealed housing; a flow control valve installed in the mouthpiece for keeping the mouthpiece open or closed; an air evacuation tube inserted into the interior of the sealed housing; a vacuum pump with a driver connected to the air evacuation tube; a shut-off valve installed in the air evacuation tube between the interior of the sealed housing and the vacuum pump; a pressure sensor located inside the interior of the sealed housing for measuring pressure in said interior; an opening in the outer wall; a transparent plate installed in the opening; a set of replaceable optical filter/waveband sensor assemblies removably installable onto the transparent plate, each replaceable optical filter/waveband filter assembly comprising a waveband filter for passing light of the discharge having a predetermined waveband and a sensor capable of converting optical signals of the discharge into electrical signals; and central processing unit, which is connected to the flow control valve, the shut-off valve, the voltage supply source, the driver of the vacuum pump, and the pressure sensor of each replaceable optical filter/waveband filter assembly for controlling operations of aforementioned devices depending on the pressure measured by the pressure sensor, wherein the housing is a cylindrical body, at least a part of the outer wall is transparent, and the counter electrode is a semi-cylindrical mirror that is located outside the outer housing and encompasses said at least a part of the outer wall, which is transparent.