EN 14683 Differential Pressure (Breathability/ΔP) Measures the airflow resistance/differential pressure/breathability of materials used in medical facemasks. Air flow: 8 liters per minute. Test area: circular; 2.5 cm diameter. Manometer used to measure the differential pressure across sample. Five measurements per mask are averaged. Performance Levels: Level 1 < 5.0 mm H2O/cm² Level 2/3 < 6.0 mm H2O/cm²