The importance of something that can help you breathe without sucking harmful particles or vapors into your lungs cannot be overstated. After all, in the prepper's adage of 3, air comes first:
3 minutes without air
3 days without water
3 weeks without food
I recommend keeping disposable masks on hand. They aren't just for people whose budget is tight. Disposable masks can be used in many different scenarios in which a gas mask may not be practical.
It's interesting to note that in China, the particulate levels due to pollution are so high that many people won't leave their homes without donning a protective mask. (source)
Classifications of masks
A major question when purchasing respirator masks is which kind to get.
There are many different classifications, but today, we'll discuss 3 popular types: the N, R, and P series masks.
The letter in the classification indicates the resistance of the mask to oil.
N – is not resistant to oil
R – is resistant to oil
P – is oil-proof
Then there are numbers, generally between 95 and 100. The number indicates the percentage of potential leakage.