The training of dogs to find narcotics and mines has revealed some differences in the dogs' perceptions of odour signature in ageing materials compared to newly manufactured ones. These differences are due to the odour signature of a material changing over time, which can be expressed as an ageing of the odour signature. A one-year pilot study was carried out to study if these differences in odour signature also apply to explosives and thus influence explosives detection dogs' perception. The study included a number of explosives commonly used in dog training. Each material was stored in one open and one sealed jar for one year. The sealed jar preserved the original odour signature while the open jar, which was ventilated, caused the odour signature to age. Following a pre-established interval, air samples were collected from the explosives in the open jars. The samples then underwent a chemical analysis in order to investigate chemical changes in the odour signature, compared to the odour signature of the material in the sealed jar. The study was concluded with a practical test where search dogs' ability to detect materials stored in open and sealed jars, respectively, was studied. Statistically significant findings revealed that the odour signature of explosives changes as they age. As a result, detection dogs' perceptions of the explosive material change. The findings in the present pilot study demonstrate that for some substances it is necessary to train and teach explosives detection dogs to find materials of varying ages. This knowledge is important to improve explosives detection dogs' knowledge of materials, and thereby the ability to detect different kinds of explosive materials. The findings form the basis for a user guide on handling, storage and exchange rate of training materials.