NOVELTY - A plant comprises at least one biofilteration bed (20, 24) formed by partially porous inert media and sprayed in a controlled manner with moistening water so that the water and the gaseous flow move in the same direction of the flow. The surface and pores of the bed adsorbed thermophile microorganisms e.g. Bacillus smithii, Aspergillus Fumigates and form colonies to metabolize the polluting components of the gaseous flow.    USE - For treatment of gaseous flow emitted from a primary purification plant (claimed) of various industries such as chemical and petrochemical processing, food processing, generation of electric power, thermal destruction of urban and industrial waste, in chipboard panel production using recycled wood.    ADVANTAGE - The plant ensures efficient removal of the pollutants in all operating conditions, proves to be an optimum purification system in situations where the polluting loads are extremely variable from both a qualitative and quantitative point of view. The combined treatment system, precipitator/thermophile biofilte, allows control of emission of dusts, volatile organic substances, formaldehyde, terpenes and ammonia into the atmosphere. Spraying water and moistening the filter bed maintains optimum growth condition within the material, keeps the pH value neutral in the filter bed, removes dissolved salts and heavy metals, and purge the metabolites and by-products from the system. The two beds are designed with different dimensions and operate in synergy to ensure efficient removal and high speed of degradation of pollutants. During periods in which the purification process is stopped for time period greater than a predetermined time limit, the filtration bed is supplied with a dummy air flow having a predetermined degree of moisture and heated to predetermined temperature to avoid deterioration in the purification properties of the colonies of the microorganisms present in the bed.    DETAILED DESCRIPTION - A plant comprises at least one biofilteration bed (20, 24) formed by partially porous inert media and sprayed in a controlled manner with moistening water so that the water and the gaseous flow move in the same direction of the flow. The surface and pores of the bed adsorbed thermophile microorganisms e.g. Bacillus smithii, Aspergillus Fumigates and form colonies to metabolize the polluting components of the gaseous flow. The spraying water is supplied at a rate of 5 litres/hour per square meter of the filter bed. The plant comprises substances in solution form with a nutrient effect for the organisms forming the colonies. phosphorus and/or potassium and/or trace elements are added to the nutrient substances.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic embodiment of the plant.    wet precipitator (10)    inlet (11)    valve (12)    flue (14)    outlet (16)    filtration bed (20, 24)    pipe (22, 30)    fan (28)    storage tank. (34)