Differences between BET specific surface area (BET SSA) values exist due to data collected in stainless steel and less thermally conductive sample holders. Not accounting for the temperature gradient along stainless steel sample holders during manometric gas adsorption measurements at cryogenic temperatures leads to errors of up to 3.2% in the BET SSA values with a relative combined standard uncertainty (RCSU) of 0.63%. A unidimensional heat flow model accurately accounts for the temperature gradient, leading to ail agreement of 0.16% between the BET SSA values for both sample holder units. (C) 2004 Elsevier Inc. All rights reserved.