Why should I breathe through my nose?
Breathing through your nose filters and warms the air that passes into the lungs. The air breathed into the passages behind your nose flows over thin bones. These are covered with sticky mucus, in which dirt particles are deposited and later swallowed. This stops your lungs from getting filled with dirt that cannot be removed. Sometimes people such as coal miners breathe in so much dust that it cannot all be filtered out. This can sometimes cause lung disease, such as emphysema.
Why is it harder to breathe when you are up a mountain?
At high altitudes that air is thinner so there is not so much oxygen in it. This means you will breathe heavily if you exert yourself by climbing. Some mountaineers carry oxygen cylinders to help them breathe. In aircraft, air is pumped in under pressure so that passengers can breathe at high altitude.
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