Method for low-temperature air separation, in which an air separation unit having a first rectification column and a second rectification column is used, - the first rectification column being operated at a first pressure level and the second rectification column being operated at a second pressure level below the first pressure level, - fluid which is oxygen-enriched compared to atmospheric air being drawn from the first rectification column in the form of one or more first material flows, - at least one portion of the fluid drawn from the first rectification column in the form of the one or more first material flows being heated in a heat exchanger, - a portion of the fluid heated in the heat exchanger being compressed using a compressor and returned to the first rectification column, - a first portion of the head gas of the first rectification column being condensed in the heat exchanger and a second portion being discharged from the air separation unit (100, 3100) in the form of at least one nitrogen-rich air product, - additional fluid containing oxygen, nitrogen and argon being drawn from the first rectification column and used as a second material flow or to form a second material flow which is transferred to the second rectification column, and - an oxygen-rich sump liquid being formed in the sump of the second rectification column and at least one portion thereof being discharged from the air separation unit (100, 200) in the form of a third material flow, characterized in that - a third rectification column is used, the second rectification column and the third rectification column being designed as parts of a double column, the third rectification column being arranged below the second rectification column, and the third rectification column being supplied with air. - the first rectification column being operated at a first pressure level and the second rectification column being operated at a second pressure level below the first pressure level, - fluid which is oxygen-enriched compared to atmospheric air being drawn from the first rectification column in the form of one or more first material flows, - at least one portion of the fluid drawn from the first rectification column in the form of the one or more first material flows being heated in a heat exchanger, - a portion of the fluid heated in the heat exchanger being compressed using a compressor and returned to the first rectification column, - a first portion of the head gas of the first rectification column being condensed in the heat exchanger and a second portion being discharged from the air separation unit (100, 3100) in the form of at least one nitrogen-rich air product, - additional fluid containing oxygen, nitrogen and argon being drawn from the first rectification column and used as a second material flow or to form a second material flow which is transferred to the second rectification column, and - an oxygen-rich sump liquid being formed in the sump of the second rectification column and at least one portion thereof being discharged from the air separation unit (100, 200) in the form of a third material flow, - a third rectification column is used, the second rectification column and the third rectification column being designed as parts of a double column, the third rectification column being arranged below the second rectification column, and the third rectification column being supplied with air.