major modifications in plants of varying capacity it is also necessary in accordance with the present invention to provide for a flame suppressor in the case of pure oxygen methane or ethane may be used as a flame suppressor the amount of the flame suppressor is controlled so as to avoid the formation of flammable mixtures in the system typically the total amount of flame suppressors is in the range of about 20 to 80 a major portion of the flame suppressor is added only during the start up since most of the flame suppressor is recycled for the process using air as the oxygen containing gas typical nitrogen concentrations are about 30 by volume and carbon dioxide concentrations about 20 as the reactor feed the oxidation reaction is conducted at a temperature in the range of from about 200 u00b0 to 500 u00b0 c and a pressure of from about 15 to 400 psig the resulting product mixture includes the alkylene oxide e g ethylene oxide unreacted alkene e g ethylene oxygen and carbon dioxide nitrogen and argon if other than pure oxygen is used as the oxidant the mixture is cooled in a cooler not shown and then sent via the line 56 to a scrubber 58 wherein water from a line 60 is used to separate the alkylene oxide from the off gases the alkylene oxide is removed from the scrubber 58 through a line 62 the off gases are sent via a line 64 to a pressure swing adsorber 66 containing two or more beds.