The ASTM F1927-20 standard provides a test method for measuring oxygen transmittance (O2 GTR) through barrier materials, permeability, and permeability under controlled relative humidity using a Coulomb Detector. This method is suitable for different types of barrier materials, including films, sheets, laminates, co-extruded plastics, or coated papers and fabrics, and can measure the steady-state transport rate of oxygen at a given temperature and Humidity conditions. This standard extends conventional no Humidity or low Humidity testing to emphasize the effect of Humidity on oxygen transmittance and is suitable for evaluating the protective performance of Encasement materials. This method can also be used as a referee test method if the buyer and seller agree on sampling, testing conditions and standards. Users should establish appropriate safety and health practices and comply with relevant regulations.