Although diethyl ether (DEE) is an excellent compression-ignition fuel, it is extremely flammable and presents a serious fire and explosion hazard. Therefore, before widespread use of DEE as an energy carrier, its safety-related issues must first be addressed. In this study, experiments of transition from deflagration to detonation (DDT) and detonation structure in DEE mist/air and DEE mist/aluminum dust/air mixtures are carried out in a horizontal tube of inner diameter 19.9 cm and length 32.4 m. The mixtures are initiated by a high-voltage electric spark and the histories of pressure wave are recorded by 17 Kistler pressure transducers in the axial direction along the tube to study the DDT process. To study the detonation structure, 4 cross-sections are chosen during the self-sustained propagation phase of the detonation where, 8 pressure transducers are arranged with the same interval angle of 45 degrees on the same tube circumference to obtain the pressure profiles. The experimental results indicate that, deflagration cannot successfully transmit to detonation in DEE mist/air mixtures when DEE concentrations are 164 and 229 g/m(3). Deflagration is observed to continuous accelerate and the onset detonation occurs at distance of 17.15 m as DEE concentration is increased up to 295 g/m(3), in which a double-headed spinning detonation structure is observed. Among the 5 different mixture composition of DEE mist/aluminum dust/air, DDT phenomenon is only observed in the mixtures of DEE mist (367 g/m(3))/aluminum dust (184 g/m(3))/air and DEE mist (314 g/m(3))/aluminum dust (230 g/m(3))/air, the run-up distances of DDT are 19.25 and 15.05 m, respectively. A single-headed spinning detonation structure is observed in DEE mist (314 g/m(3))/aluminum dust (230 g/m(3))/air mixture. (c) 2013 Elsevier Ltd. All rights reserved.