An air purification installation comprising: - a particle filtration unit comprising an air inlet and an air outlet, said unit being capable of retaining at least some of the particles present in the incoming air in order to provide an air outlet with a reduced particle content, • a treatment unit comprising at least one treatment agent, and: - two fluid circuits passing through at least one treatment agent: - an air circuit comprising an air inlet in fluid connection with the air outlet of the filtration unit and an air outlet, and - a washing fluid circuit comprising a washing fluid inlet and a washing fluid outlet, - a system for regulating the fluid flow rate in each of the circuits configured so that when the fluid in one of the circuits is flowing, the fluid in the other circuit is not flowing, with at least one treatment agent being capable of capturing at least some of the nitrogen oxides (NOx) present in the incoming air in order to supply air with a reduced NOx content at the outlet, the washing fluid leaving the treatment unit with an increased NOx content, • a unit for capturing carbon and nitrogen oxides, comprising at least one bioreactor containing microalgae capable of converting carbon dioxide and nitrogen oxides into organic compounds by photosynthesis, the capturing unit having an air inlet, a fluid inlet in fluid connection with the washing fluid outlet of the treatment unit, an air outlet and a fluid outlet, the air leaving the capturing unit having a reduced carbon content, in particular of CO 2, the fluid leaving the capturing unit having a reduced NOx content. - a particle filtration unit comprising an air inlet and an air outlet, said unit being capable of retaining at least some of the particles present in the incoming air in order to provide an air outlet with a reduced particle content, • a treatment unit comprising at least one treatment agent, and: - two fluid circuits passing through at least one treatment agent: - an air circuit comprising an air inlet in fluid connection with the air outlet of the filtration unit and an air outlet, and - a washing fluid circuit comprising a washing fluid inlet and a washing fluid outlet, - a system for regulating the fluid flow rate in each of the circuits configured so that when the fluid in one of the circuits is flowing, the fluid in the other circuit is not flowing, with at least one treatment agent being capable of capturing at least some of the nitrogen oxides (NOx) present in the incoming air in order to supply air with a reduced NOx content at the outlet, the washing fluid leaving the treatment unit with an increased NOx content, - two fluid circuits passing through at least one treatment agent: - an air circuit comprising an air inlet in fluid connection with the air outlet of the filtration unit and an air outlet, and - a washing fluid circuit comprising a washing fluid inlet and a washing fluid outlet, - an air circuit comprising an air inlet in fluid connection with the air outlet of the filtration unit and an air outlet, and - a washing fluid circuit comprising a washing fluid inlet and a washing fluid outlet, - a system for regulating the fluid flow rate in each of the circuits configured so that when the fluid in one of the circuits is flowing, the fluid in the other circuit is not flowing, with at least one treatment agent being capable of capturing at least some of the nitrogen oxides (NOx) present in the incoming air in order to supply air with a reduced NOx content at the outlet, the washing fluid leaving the treatment unit with an increased NOx content, • a unit for capturing carbon and nitrogen oxides, comprising at least one bioreactor containing microalgae capable of converting carbon dioxide and nitrogen oxides into organic compounds by photosynthesis, the capturing unit having an air inlet, a fluid inlet in fluid connection with the washing fluid outlet of the treatment unit, an air outlet and a fluid outlet, the air leaving the capturing unit having a reduced carbon content, in particular of CO 2, the fluid leaving the capturing unit having a reduced NOx content.