Fig. 2. Study flow.
A: horizontal 3-fold mask, B: horizontal 3-fold mask with adjustable ear-loops length, C: vertical 2-fold mask.
FF = fit factor, OSHA = occupational safety and health administration.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.