The device (1) has an adsorber (2) with a volume, V, through which an exhaust gas can flow. The volume can be calculated using an equation and the average values for the mass flow and temperature of the exhaust gas. The volume corresponds to the equation V = a + bt + c/m + dt 2> + e/(m 2>) + ft/m + gt 3> + h/(m 3>) + it/(m 2>) + kt 2>/m, where t is the average exhaust gas temperature, m is the average exhaust gas mass flow, a = 0.1660393, b = 0.0033635701, c = -1.7023186, d = 6.5277225 X 10 -> 6>, e = 195.657, f = -0.1373556, g = -9.0343024 X 10 -> 9>, h = -1273.9098, i = 1.0172767 and k = -1.442512 X 10 -> 5>.