Disclosed is a process for removing carbon monoxide from a gas containing carbon monoxide, the gas being selected from hydrogen gas and/or one or more gaseous aliphatic hydrocarbons or a mixture thereof. The process comprises bringing the gas into contact with a complex metal aluminium hydride in a reaction vessel, wherein the metal aluminium hydride is selected from the group which consists of one or more compounds of Formula I Me.sup.x+[AlH.sub.4].sup..sub.x with x=1-5, of Formula II Me.sub.y.sup.w+[AlH.sub.6].sup.3.sub.z with w.Math.y=3z, and of Formula III Me.sub.p.sup.q+[AlH.sub.5].sup.2.sub.r with p.Math.q=2r, wherein Me represents one or more alkalis or alkaline-earth metals.