TAPPI T 547 OM

Abstract

This method is used to measure the air permeance of a circular area of paper using a pressure differential of approximately 10 kPa (1.5 psig). In order to accommodate a wide range of paper products, rubber clamping plates are available for five commonly used orifice diameters: 9.5 mm (0.375 in.), 19.1 mm (0.75 in.), 38.1 mm (1.50 in.), 57.2 mm (2.25 in.), and 76.2 mm (3.00 in.). The air flow range for this method is 0 to 3348 mL/min (0 to 400 Sheffield units). Instruments are available with either variable area flowmeters (glass tubes with internal tapers and floats) or electronic mass flowmeters. <br>This method measures the air that passes through the test specimen, along with any possible leakage of air across the surface; therefore it is unsuitable for papers with rough surfaces which cannot be securely clamped so as to avoid significant surface leakage. <br>For other methods of measuring the air resistance of paper using a 28.6 mm (1.125 in.) orifice diameter, refer to TAPPI T 460 "Air Resistance of Paper (Gurley Method)" or a test that operates at a pressure differential of 1.22 kPa, or TAPPI T 536 "Resistance of Paper to Passage of Air (High Pressure Method)" for 3 kPa.