A discussion of the application of plastic bags is presented along with results of an experiment in which two plastic film materials were used to contain the vapors of four different chemicals at concentrations bracketing the current (1969) TLV. The four chemicals—benzene, methyl alcohol, methyl isobutyl ketone, and methylene chloride—are members of classes of important compounds used in many industrial applications. Additional studies using reactive mixtures under various environmental conditions are needed to determine retention characteristics under conditions similar to the conditions under which the samples are collected or standards prepared.