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

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204. Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information N it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)2 SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION I AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTTest 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' for unencumbered ventilation and work activities that spanned from mild to exhaustive. The mean minute volume of the distribution was 38.5 ± 16.6 L'min-1, and the median was 33.6 L-minin. Based on an empirical relationship between minute volume and peak inspiratory flow (PIF), peak flows between 72 L'min-' and 183 L'min-1 would be expected for the mean minute volume for 38.5 L'min'. The anticipated range of PIF rates for the 9 5 dh percentile minute volume is between 182 L-min-' and 295 L-min-'. The results of this literature review suggest an increase in cyclic flow rates used for respirator certification testing should be considered to better represent ventilation rates found in the workplace. Blank EXECUTIVE SUMMARY Test methods currently used by the National Institute for Occupational Safety and Health (NIOSH) are designed to assure that all respirators of a given type will meet a minimum level of efficacy when tested under standard laboratory protocols. The relevance and adequacy of airflow rates used in respirator certification testing has been a longstanding debate. The concern is that the current test flow rates substantially underestimate real world values, implying that filters certified under existing standards may not provide adequate protection. For qualifying airpurifying respirators (APRs), the primar...

Reusable elastomeric air-purifying respirators: Physiologic impact on health care workers

“…19 A recent review concluded that respirator use has little impact on minute volume during resting or low-intensity work conditions like those normally encountered in health care environments. 20 Mean absolute increases in transcutaneous carbon dioxide with the EAPR at 1.7 mph (13.2 mm Hg) and 2.5 mph (12.1 mm Hg) were not significantly different from controls (P 5 .09, P 5 .27, respectively). Of concern is the finding that mean transcutaneous carbon dioxide levels, averaged over the course of the last 15 minutes of the EAPR use, were elevated (ie, .45 mm Hg) in 4 of 10 subjects at the 1.7-mph work rate (range, 46-56 mm Hg) and 5 of 10 subjects at the 2.5-mph work rate (range, 45.4-62.8 mm Hg), despite the EAPR being equipped with an exhalation valve that presumably allows for a smaller proportion of the exhaled breath (and associated carbon dioxide) to be retained in the respirator dead space (all subjects were asymptomatic of hypercapnia).…”

Filter Performance of N99 and N95 Facepiece Respirators Against Viruses and Ultrafine Particles

“…Consensus is not found in the literature for a representative occupational ventilation rate for PIF. However, the range of PIFs for the 95 th percentile minute volume for occupational tasks is estimated to range between 182 and 295 L/min (Caretti et al, 2004). Therefore, the choice of 150 L/min may underestimate a "worst case" PIF.…”

“…First, the rate established by the NIOSH protocol (85 L/min) may be exceeded during more strenuous occupational tasks. Second, modern FFR media relies upon electret properties for much of the overall filtration efficiency (Martin and Moyer, 2000;Caretti et al, 2004). For ultrafine particles, the primary filter capture mechanisms are diffusion and electrostatic interaction, which are both strongly dependent upon respirator face velocity.…”

Viable Viral Efficiency of N95 and P100 Respirator Filters at Constant and Cyclic Flow

“…(12) Additionally, peak flow rates measured during exhaustive work can exceed the 85 L/min NIOSH certification flow. (14) A high breathing rate and particles sized within the MPPS range may result in aerosol penetration exceeding that associated with the stated certification level.…”