Described is an article which dispenses at a constant rate a volatile composition of matter into the atmosphere surrounding the article which volatile composition of matter can be, for example, a perfume composition or air freshener, which article is a container which is a hollow totally enclosed flexible, rigid or partially flexible-partially rigid structure comprising a thin shell totally enclosing an inner void, with the thin shell having a part thereof as a microporous polymer which contains a plurality of finite filler particles which that when the article is located in the ambient environment, the volatile material molecules are passed through the microporous polymer by means of an adsorption desorption mechanism or by means of capillary action. The volatile substance which is a composition of matter is enabled to pass through the microporous polymer at a constant mass flow rate of both the individual volatile components and the total composition. Thus, the composition of matter passing through the microporous polymer remains unchanged insofar as its composition is concerned. The invention is enabled using a microporous polymer having the property of transporting water vapor at a rate of between 100 up to a 1000 g/m.sup.2 /day at about 25.degree. C. and at about 50% relative humidity at about atmospheric pressure and having an air transport rate of 100-20,000 Gurley seconds (gs) and a thickness in the range of from about 0.01 mils up to about 20 mils.