Whereas flammable gas explosions under standard atmospheric conditions have been thoroughly researched, those under oxygen-enriched atmospheres (OEAs) have rarely been discussed. In response to an OEA explosion caused by a control malfunction at a Taiwanese manufacturing plant, this research conducted experiments to obtain and analyze explosion data. Ethylene gas was introduced into a 20-L spherical vessel under standard and OEA conditions. Results showed that the rise in pressure versus time is consistent with theoretical predictions for 19.5% and 30.0% oxygen concentrations, but flammable gases under higher oxygen atmospheres had significantly higher maximum rate-of-pressure rise values, maximum pressures, and burning velocity when compared to standard atmospheric conditions. These results proved such conditions to be extremely hazardous, and they called for applicability reconsiderations as well as the redesign of pressure-relief vents, suppression systems, and isolation systems where such conditions may occur. Moreover, explosion tests should be performed for processes under their designed or potential atmospheric scenarios, such as OEAs, before commencing production. (C) 2017 Elsevier Ltd. All rights reserved.