A study was conducted to investigate the influence of the atmospheric pressure, from 101,325 to 60,000 Pa (corresponding from 0 to 4217 m of altitude), on the heat and mass transfer rates of desiccant wheels (hygroscopic matrix of silica gel RD), assuming fixed-mass airflow rates and fixed inlet states for the process and regeneration airflows, defined by the respective inlet temperatures and water vapour contents. The results show a generic reduction of the heat and mass transfer rates as the atmospheric pressure decreases, an effect that is more pronounced for short channel wheels and high airflow rates. Correlations based on the numerical results are presented for the correction of the heat and mass transfer rates when the desiccant wheels are operating at non-standard atmospheric pressure. (C) 2010 Elsevier Ltd. All rights reserved. A study