November 24, 2021

NIOSH Tests Effects of Stockpiling Respirators on Fit, Strap Elasticity

A study conducted by NIOSH found some substantial differences between certain respirator products in the Strategic National Stockpile and models purchased on the open market, according to a report (PDF) released earlier this month. The SNS is the United States’ reserve of medical supplies, including protective equipment, vaccines, and antibiotics. The study was requested by SNS personnel to evaluate the effects of stockpiling on the viability of respirators. Beginning in 2017, NIOSH collected approximately 4,000 N95 filtering facepiece respirators (FFRs) from 10 SNS facilities. The new report describes the fit-testing performance of respirators collected from a facility located within Region 9, as designated by the Department of Health and Human Services. Region 9 represents Arizona, California, Hawaii, and Nevada.

At the time the tests were conducted, the respirators from this facility had been stored for nine to 13 years, well past the manufacturers’ recommended five-year shelf life. Some models purchased on the open market, which the study identifies as the control respirators, had a higher fit factor—a measure of how well the devices seal to the faces of users—than stockpiled models. In other cases, users were able to achieve better fit with the stockpiled models.

Fit factors were measured using the quantitative method explained in Appendix A of OSHA’s respiratory protection standard. Following this method, OSHA requires users to attain a fit factor of at least 100 prior to using the respirator during work tasks. Each user who participated in the study donned each respirator multiple times. For the control respirators, 48 percent of 503 total donnings achieved a fit factor of at least 100, while 41 percent of 1,165 total donnings of the stockpiled respirators achieved a fit factor of at least 100. Users achieved a passing fit factor with 67 percent of the 84 control respirators and 55 percent of the 293 stockpiled respirators.

The study also identified variances in strap elasticity between the control respirators and stockpiled models. Some stockpiled respirators had stiffer straps while others were less stiff than the control models. However, researchers were unable to conclude whether the differences in stiffness were enough to affect the fit of the respirators.

More information is available in the NIOSH report (PDF) and the agency’s press release. Additional reports characterizing the performance of respirators in other SNS facilities are collected on the NIOSH website.