and microporous membranes is well documented in textbooks for example in r e kesting and a k fritzsche polymeric gas separation membranes wiley 1983 and in r e kesting synthetic polymer membranes wiley 1985 the art of making microporous inorganic membranes is well documented for example in c j brinker and g w scherer sol gel science academic press 1990 in one simple method the coating solution is filled in the vessel and its appurtenances the coating solution is then drained and the surfaces are dried by volatilization of the solvents either by natural evaporation or by forced evaporation caused by heating the surfaces using air or inert gas circulation or the combination thereof alternatively the coatings can be done by a spray coating method or other methods known to those skilled in the coating art pre prepared semi permeably material layers in the form of membranes may also be placed on the odorant layer to encapsulate the odorant layer such semi permeable membranes can either be commercially purchased or fabricated separately using the known art described for example in the references cited herein example 2 the odorant material can be sorbed with an appropriate substrate where it exists in a liquid condensed form and is held there by capillary forces the thus odorant containing sorbed material is placed in the gas storage vessel in a predetermined quantity at the temperature and pressure of the gas the odorant material establishes equilibrium with the gas and provides the.