On February 4, Secretary of Defense Lloyd J. Austin III signed a memo that, effective immediately, directs all individuals on military installations and all individuals performing official duties on behalf of the Department from any location other than the individual’s home, including outdoor shared spaces, to wear masks in accordance with the most current Centers for Disease Control and Prevention (CDC) guidelines. 

Individuals must wear masks continuously while on military installations except:  (1) when an individual is alone in an office with floor-to-ceiling walls with a closed door; (2) for brief periods of time when eating and drinking while maintaining distancing in accordance with CDC guidelines and instructions from commanders and supervisors; (3) when the mask is required to be lowered briefly for identification or security purposes; and (4) when necessary to reasonably accommodate an individual with a disability. Individuals must consistently wear a mask that covers the nose and mouth and that comports with all current guidance from the CDC and the Occupational Safety and Health Administration.

Categorical or case-by-case exceptions to these requirements for Service members and their families in environments other than office spaces that are necessary for military readiness, that are related to living on a military installation, or that are related to mask wearing by children (so long as such exceptions are consistent with CDC guidelines for mask wearing by children) may be granted in writing by Department of Defense (DOD) Component heads and should include appropriate alternative safeguards whenever feasible, such as additional physical distancing measures or additional testing consistent with DOD testing protocols.

DOD Components will comply with applicable labor relations obligations to the extent such obligations do not conflict with the agency's ability to conduct operations during this emergency.

The memo can be found here.