There is not much definitive research how well face masks any kind work prevent any disease, and even less research a new disease like COVID-19.

N95 masks generally are best preventing someone catching a virus. When used correctly, they fit closely the face and block more particles than most other masks.
However, many people do not use them correctly. They often do not get a tight enough fit, which largely defeats the purpose of the masks.
Dr. Chongfei Jin works Patient First the state Virginia. He said there are many videos available line that show how wear the mask the right way.
He said, “I just want remind the public three things: Avoid . Avoid . And cover your nose as well.”

Health care workers are facing serious shortages part because the panicked public has bought N95 masks themselves.
"If they run masks, then it's very difficult for them stay healthy take care you and me when we get sick," said Jon Andrus