Available leakage models of gasket seal are stated in the paper.The sealing test of noncompressed asbestos gaskets and flexible graphite reinforced gaskets are carried out and the parameters of the leakage rate formula of porous media model are obtained.On the basis of this work it is possible that the seal design procedure prescribed in the codes in effect and mainly based on the strength criterion will be developed into the “tightness design procedure”based on the criterion of the maximal allowable leakage rate. Available leakage models of gasket seals are stated in the paper. Sealing test of noncompressed asbestos gaskets and flexible graphite reinforced gaskets are carried out and the parameters of the leakage rate formula of porous media model are obtained. On the basis of this work it is possible that the seal design procedure prescribed in the codes in effect and mainly based on the strength criterion will be developed into “tightness design procedure” based on the criterion of the maximal allowable leakage rate.