Method for manufacturing a capsule (12) to contain a substance (14, 130) that is required to be contained in airtight isolation, the method including the steps of: providing a first portion (2) of flexible material capsule to contain the substance (14), the first capsule portion (2) having a closed end (5), an opposite open end (6) and a defined predetermined length dimension between the ends (5,6) thereof； providing a second portion (4) of flexible material capsule having a closed end (7), an opposite open end (8) and a defined predetermined length dimension between the ends (7.8) thereof, which is more short that the length dimension of the first capsule portion (2)； at least partially filling the first portion (2) of the capsule with the substance (14)； insert the closed end (7) of the second capsule portion (4) into the open end (6) of the first capsule portion (2) such that an area of the second capsule portion (4) overlaps with an area of the first capsule portion (2) so that it closes the open end (6) of the first capsule portion (2) and defines a chamber (104) within which the substance (14) is contained, characterized because the step of inserting the closed end (7) of the second capsule portion (4) into the open end (6) of the first capsule portion (2) includes inserting the closed end (7) of the second portion (4) ) of the capsule until the open ends (6, 8) of the first portion (2) of the capsule and the second portion (4) of the capsule are aligned at the same level with each other and after that, join together the ends (6 , 8) open aligned at the same level of the first capsule portion (2) and the second capsule portion (4), for and hermetically seal the chamber (104).Método para fabricar una cápsula (12) para contener una sustancia (14, 130) que se requiere que esté contenida en aislamiento hermético, incluyendo el método las etapas de: proporcionar una primera porción (2) de cápsula de material flexible para contener la sustancia (14), teniendo la pri
