Microencapsulation of the principal marking agent for detection of explosives, 2,3-dimethyl-2,3-dinitrobutane (DMNB), has been investigated as a means of extending the lifetime of the marking agent. DMNB sublimes from explosives, into which it has been incorporated and is detected by GC/MS. TGA was used to characterize and optimize the type and thickness of the coating. Results of various TGA tests are presented, to show that microencapsulation of DMNB is effective at substantially reducing the emission rate of DMNB, and thus increasing the lifetime for detection of explosives. As an extension to this study, a simple but novel method for measuring the permeability of DMNB vapor through various materials was developed using TGA and the solubility-diffusion model. Preliminary results for permeability through polystyrene and polyethylene are presented. Crown Copyright