The TAPPI T 547 standard sets out a method for determining the air permeability of paper and Cardboard using the Sheffield method. The vapor transmission rate refers to the ability of air to pass through paper or Cardboard under specific conditions, and is an important indicator to measure its porosity and breathability performance. The standard specifies in detail the test equipment, sample preparation, test conditions and operating procedures to ensure the accuracy and Repeatability of the measurement results. Through this method, the suitability of paper and Cardboard for applications such as Encasement and printing can be evaluated. The standard applies to all types of paper and Cardboard, especially for materials with high vapor transmission rates.