The breakthrough behaviour of activated charcoal cloth samples against an oxygen analogue (OA) of sulphur mustard has been studied using the modified Wheeler equation. Activated charcoal cloth samples having different surface area values in the range of 481 to 1290 m2/g were used for this purpose. Breakthrough behaviour was found to depend on the properties of the activated charcoal cloth, properties of the OA and the adsorption conditions. Activated charcoal cloth with a high surface area of 1290 m2/g, relatively large surface density of 160 g/m2 and coarser fiber structure exhibited better kinetic saturation capacity value, 0.19 g/g, against OA vapours when compared to others, thus confirming its potential use in foldable masks for protection against chemical warfare agents.