The invention concerns a method for storing a NO/N2 mixture in a packaging container (6) comprising an inner volume, characterized in that it holds a NO/N2 gaseous mixture containing between 1200 and 4500 ppm by volume of NO, the remainder being nitrogen, at a pressure of at least 100 bar in the inner volume of said container (6), the inner volume being less than or equal to 12 litres (water equivalent).