Both the CDC and State of California have said that face coverings can help slow the spread of COVID-19
Governor Gavin Newsom has repeatedly said face coverings can supplement but not replace such behaviors such as staying at home, maintaining physical distance and hand washing. State health officials have expressed concern the masks could lull people into a false sense of security and cause them to avoid more critical distancing behaviors. They also remain worried that residents may try to obtain N95 or surgical masks as hospitals struggle to find enough for their workers.
Newsom has repeated:
We have been very clear that if you are going into an environment where physical distancing is all but impossible — for example, into a grocery store with small aisles and a long queue — that we do believe it would be additive and beneficial to have a face cover”
A significant portion of individuals with Coronavirus lack symptoms (they are “asymptomatic”). Even those who eventually develop symptoms (“pre-symptomatic”) can transmit the virus to others before showing symptoms.
This means that the virus can spread between people interacting in close proximity—for example, speaking, coughing, or sneezing—even if those people are not exhibiting symptoms.
Therefore, CDC recommends wearing cloth face coverings in public settings where social distancing is not feasible.
Face Coverings
Face Coverings are loose-fitting, disposable devices and can be home-made. Face coverings should be used in public settings where social distancing is not feasible.

N-95 Filtering Facepiece Respirators
A standard (non-surgical) N95 Filtering Facepiece Respirator (FFR) will filter out at least 95% of very small (0.3 micron) airborne particles, including bacteria and viruses. (N means that the mask is not oil resistant). Photo below.
N95 Respirators are for first responders and health care providers who are caring for or contacting actual or suspected COVID-19 patients.
Additionally, the CDC has a page dedicated to question about PPE or Personal Protective Equipment
