Workplace Breathing Rates: Defining Anticipated Values and Ranges for Respirator Certification Testing

Abstract : Test methods currently used by the National Institute for Occupational Safety and Health (NIOSH) are designed to assure that respirators meet a minimum level of efficacy when tested under standard laboratory protocols. For air-purifying respirators (APRs), the primary performance tests most affected by airflow rate are filter gas-life capacity, particulate filter efficiency, and respirator breathing resistances. Presently, NIOSH measures all three parameters using constant-rate airflow conditions. An analysis of the measured and estimated minute volumes contained in the literature indicated a range from about 8 to 162 L min(exp -1) for unencumbered ventilation and work activities that spanned from mild to exhaustive. Based on an empirical relationship between minute volume and peak inspiratory flow (PIF), peak flows between 72 min(exp-1) and 183 L min (exp -1) would be expected for the mean minute volume for 38.5 L min(exp -1). The anticipated range of PIF rates for the 95th percentile minute volume is between 182 L min(exp -1) and 295 min(exp -1). The results of this literature review suggest an increases in cyclic flow rates used for respirator certification testing should be considered to better represent ventilation rates found in the workplace.