CDC recommends KN95 respirators ... approved under equivalent evaluation standards as the NIOSH-approved N95 respirators
"Other countries approve respirators for occupational use and approve respirators to these standards. These products are evaluated using some methods similar to those used by NIOSH, and some methods that are different, but are expected to protect HCPs. These respirators are expected to provide protection to workers. Those with equivalent or similar protection to NIOSH-approved respirators may be available to provide respiratory protection to workers exposed to harmful airborne particulate matter. These devices are expected to be suitable alternatives to provide protection during the COVID-19 response."
(March 17, 2020, Center for Disease Control and Prevention, www.cdc.gov/coronavirus/...)