Masks are controversial because there are clear positives and negatives, and how they net can vary with the circumstance.  Since the chances of any infection is in part related to the size of the innoculum (the number of  infectious pathogens that forge the initial attack), masks can make the innoculum smaller both going and coming.  However, mask-wearers continuously inhale whatever on the inside of the mask.  There are toxic and psychological aspects to mask-wearing.  Therefore, wearing a mask and using other precautions is prudent when in large groups and/or in close proximity. Finally, the more your immune system has its warriors properly armed, the better the chance of fighting the virus.

How to Make Your Own Face Mask at Home1

How to Sew a Face Mask – The New York Times

My Advice on Masks for Coronavirus _ MyHealth Beijing

1910.134 App B-1 – User Seal Check Procedures (Mandatory). _ Occupational Safety and Health Administration