Characterization of a porous medium permeable by gas nmr polarizes

The invention concerns the characterisation of porous permeable objects, comprising the following steps: placing the object (2) in a sealed chamber (4); depressurising the chamber (4) containing said object (2); measuring the residual pressure prevailing in the depressurised chamber (4); introducing an amount of polarised gas in the depressurised chamber (4); measuring the pressure prevailing in the chamber (4) after said amount of polarised gas has been introduced; determining the density of the polarised gas introduced in the chamber (4) from said pressure measurements; measuring by NMR the mass quantity of polarised gas contained in a known volume of the object (2) placed in the sealed chamber (4); determining the porosity of the object (2) by calculating the ratio of polarised gas mass quantity/ polarised gas density introduced in the chamber (4).