FOREWORD This code was formulated by the Topical committee on production Technology of the Central Committee on Drilling and Production Practice in the Division of Production of the American Petroleum Institute. 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 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.