Purpose The purpose of this code is to facilitate comparisons and coordination of permeability measurements on porous media as made in various laboratories by the adoption of uniform notation and dimensionally equivalent units. It is the further purpose to define the conditions of test and to point out sources of error commonly encountered@ not with the view to standardize the detailed technique of measurement but rather to insure that reported values are free from inaccuracies caused by faulty methods and improper conditions of test.