A New Simplified Technique for Measuring Inspiratory Flow Characteristics

Filter penetration is an important factor in determining protection provided by a respirator to workers. However, filter performance is still tested at flow rates based on flow rate data collected in the 1940s which where limited to the technologies available at the time. To accurately chart the human breathing cycle when wearing a respirator, it is important, to achieve readings with as high a resolution as possible. Since the inspiratory airflow in human breathing reaches its peak very rapidly, particularly in conjunction with speech (Holm’er 2003), a true breathing curve can only be generated by an instrument capable of sampling the airflow almost instantaneously. With the aim of achieving high resolution readings, a simplified type of flow meter was designed for measuring the inspiratory airflow characteristics in humans at a rate of fifty times per second (50 Hz). This paper describes the design of the new simplified flow meter, its construction, its calibration, and the continuous monitoring and verification of its performance. Subsequent to data collection, the raw flow meter readings were corrected to true flow rates using a regression equation derived from the calibration data.