During the SARS outbreak, and in some countries under normal conditions, we saw people wearing surgical masks. The purpose of these masks might surprise you.
Surgical masks aren't designed to protect you. They're designed to protect those around you from the germs you might be spreading, by blocking those droplets you shoot out when you sneeze or cough. Surgical masks also divert airflow so that you don't end up breathing directly on the people you're talking to.
You might be wondering why masks don't work the other way too. Well, imagine trying to blow out a candle by sucking in your breath. You'd have to hold the candle close to your face, right?
That's because the air we breathe in comes from all directions, while the air we exhale is more directed. So for a mask to filter the air you're inhaling, it would need to form a seal around your mouth and nose. Surgical masks aren't designed to do that. Instead, doctors protect themselves from airborne infections by wearing special snug-fitting respiratory masks, which filter out about ninety-five percent of a given concentration of particles.
You could purchase a respiratory mask, but some require a professional fitting, and all are pretty uncomfortable for long periods of time. Plus, keep in mind that most colds spread from mouth to hand, and hand to mouth. So while a mask might help somewhat, and also help keep you from touching your nose and mouth, the number one way to protect yourself from the common cold is to wash your hands in soap and water.