Ageing results of three test wire detectors when filled with dimethyl ether (DME) are presented. DME gas was analyzed before and during the tests for the presence of electronegative impurities, such as Freons. A strong dependence of the rate of ageing on the wire composition was observed. The resistive wires, such as Stablohm and Nicotin, produced fast ageing. Also, even the best available purified DME, as of today, used with gold-plated wires, produced some slow ageing. The rate of amplitude decrease depended on the Freon impurity level.