Why can we breathe in humid air?


If getting water in our lungs is dangerous, and humid air can contains a lot of water, sometimes so much that *everything* it touches gets wet, then why is it okay to breathe this air?

In: 6

Liquid water in large amounts is dangerous because it prevents the exchange of air.

Our breath has water vapour in it to begin with because some water comes out of the blood in the lungs and is then breathed out. The water in the air when it is humid is water vapour (a gas) and not liquid water.

Condensation happens when warm, humid air drops in temperature. The water capacity of air drops as temperature drops, so the excess humidity (water vapor) condenses on anything it can (surfaces, dust particles, etc.).

When you’re breathing air, in most cases, your lungs will be the warmest that the air will get. Since the air is warming up as you breathe it in, it will never condense water inside your body. Instead, it will draw some water from your body/lungs, because it’s warming up and your lungs are so moist.

The only situation where this is reversed is when you are in a super humid, super warm jungle, where the air is *higher* than human body temperature and is also completely saturated with water. But even then, the air will cool as it enters your mouth and throat, condensing the water there. By the time it gets to your lungs, it’ll be “stable” (not condensing water) at body temperature. This is all ignoring that, if you are in a situation with air temperatures above body temperature and completely humid air, you are at severe and imminent risk of heat stroke.

It’s not the presence of H2O molecules that is the problem, it’s when so much water gets in your lungs that it physically blocks enough air from entering the lungs.

Air is a mixture of gases, water vapor being a major component. Ambient air is actually only 21% oxygen. Life has evolved to extract sufficient oxygen from this mixture. Breathing very dry air is actually uncomfortably because it dries out your airways which require some moisture to function optimally. Your nose is an ~impressively~ good humidifier to minimize this problem.