N95 masks that are well past their expiration date or have been used and re-sterilized are acceptable alternatives to standard new single-use N95 masks, new research indicates.

Hospitals are also turning to imported or donated masks that are not approved by the National Institute for Occupational Safety and Health (NIOSH) as a potential replacement for limited NIOSH-approved N95 masks.

Emily Sickbert-Bennett, PhD, with the Infection Prevention Department, University of North Carolina Health Care, Chapel Hill, and colleagues tested the fitted filtration efficiencies (FFEs) of 29 different fitted face mask alternatives worn by a male and female volunteer in a custom-built exposure chamber. .

"These respirators, which have elastic ear loops and a vertical fold design, were least effective when the test individual bent at the waist and looked up and down," say the researchers.

Not surprisingly, surgical and procedure masks had substantially lower average FFEs than the N95 respirators, they found.

In all tests, the FFE of masks secured with ties outperformed those secured with ear loops, researchers say.

Moreover, these findings illustrate the importance of fit for maximizing the overall effectiveness of both respirators and masks," the researchers write.

The coauthors of a linked editorial say despite the apparent "imperfect" FFE of non-NIOSH approved respirators and surgical masks in the laboratory, "there is reason for optimism regarding their real-world effectiveness.".

"Frontline clinicians and essential health care workers who engage in the highest risk procedures should be afforded the highest level of protection with NIOSH-approved N95 respirators," they point out.

The current study shows that reprocessed use and expired supply of N95 masks are "safe and offer excellent alternatives to standard single-use N95 masks.

Despite lower filtration efficiencies of submicron particles, surgical masks and other N95 alternatives likely provide adequate protection against transmission for routine care.".