Singapore is having an episode of its regular hazy season because of smoke from forest fires. Some people have been using surgical masks like the the one shown at the bottom of this post, presumably for health reasons.
I know the mask has to stop unwanted particles from getting through. But at the same time, it has to let in enough air to breathe. I understand how it could work to keep people from getting sick - after all, bacteria are much larger than air molecules, so you could have little holes that let air through but keep bacteria out.
But aren't smoke particles too small to be stopped in this way? I think of smoke as a gas (it certainly looks that way, e.g., coming off a candle or a piece of burning incense). Are smoke particles as small as the molecules that I need to breathe in to survive? If they are, how can this mask differentiate between, say, oxygen and smoke?