The tomographic measurement technique enables the measurement of local water vapour concentrations at the exit of a packed bed adsorber using near infra-red. This is realized by extending the adsorption column with a hollow glass cylinder that serves as the measurement cross-section. The glass is transilluminated from three directions with three light-sheets. The light absorption by water vapour is measured with three InGaAs photodiode arrays and these projections are used for the tomographic reconstruction of the concentration fields. For low water vapour concentrations (c < 9E - 4 mol/l) an error below 8% is reported. Concentration field measurements during adsorption show the early breakthrough near the column wall due to channeling effects at a low ratio between tube and particle diameter. (C) 2004 Elsevier Ltd. All rights reserved.