FDA requirements for Facemasks:

“Most types of medical devices, imported to the US are regulated by the FDA. As a US importer, you must either provide a Premarket notification 510 (k), or obtain a Premarket Approval.”

Also of note: “…a supplier cannot be FDA certified. It comes down to the product, not the company.”
Link for FDA requirements

“FDA, upon its own initiative, is exempting N95 filtering facepiece respirators (FFRs) and surgical N95 respirators (herein collectively referred to as N95s) from 510(k), subject to the conditions and limitations described in this section.”

This doesn’t mean that masks don’t have FDA regulations. They’re controlled under NIOSH approval.

“As described in the MOU, the following conditions must be met for N95s to be 510(k) exempt: (1) application submitted to NIOSH is determined not to exceed the CDC's and FDA's mutually agreed upon threshold evaluation criteria and (2) such applicants must have met approval criteria and have NIOSH approval.”
Link for 510(k) exemption details

Or more specifically N95 (United States NIOSH-42CFR84)

Our masks (as are many) are manufactured in China, and are controlled under the equivalent Chinese standard: KN95 (China GB2626-2006)

Please see page 2 of the link from 3M titled "Comparison of FFP2, KN95, and N95 and Other Filtering Facepiece
Respirator Classes" which explains the different standards between the US, Europe, China and other countries.
Link for N95 vs KN95

The filter performance must be ≥ 95% efficient for each of these masks to meet their respective government standards.