Why is it that we can breathe in steam/water vapor, and not worry about small amounts of water getting into our lungs?

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I take a lot of hot showers, and sometimes I find myself wondering why I am able to breathe in the steam around me and not worry about any water-in-lungs related health concerns. How is breathing in steam different than breathing in small amounts of water droplets?

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18 Answers

Anonymous 0 Comments

Couple reasons:

1. Water vapor is a gas, while droplets are liquids that are *suspended* in gas. Your lungs are very capable of propelling gasses out with each breath, but droplets will touch your lungs and “fall” out of suspension, becoming liquid water in your lungs. Small amounts will simply evaporate over a short period of time, but large amounts can be problematic as they’ll coat the surfaces of your lungs and pool, decreasing the surface available to exchange oxygen in air.

2. Vapor (a gas) condenses most readily on cold surfaces (like on the outside of a cold drink can), and less readily on warm surfaces. Your lungs are warm, so vapor doesn’t easily condense on the surfaces. Some will, but it takes a lot of vapor at a higher temperature than the body. At that point you’re likely more worried about steam burns, and you have other problems.

3. Droplets carry more water than vapor. A breath full of water droplets has more water than a breath with high concentration of water vapor. Lots of water is bad, less water is not really a problem because your lungs can expel it easily enough.

4. Your airway isn’t just a straight path to your lungs. Your airways, especially when breathing through your nose, are absolutely coated with little hairs that I can’t remember the name of. These provide a high surface area for water droplets to contact on before they get to your lungs, and they help filter out some droplets before they get to your lungs. When these get disturbed enough, they trigger a cough reflex, which helps propel the droplets out of your airway before they get into your lungs.

5. Your lungs are capable of absorbing some water. At a very basic level, your lungs are just a way to get a very large surface area between air (oxygen) and your blood, so that oxygen can be passed into your blood and CO2 can be passed out. It’s a mass transfer system, which depends on surface area. Your lungs work well for the same reason that a towel dries faster when you hang it up vs leaving it balled up. In the same way that they absorb and desorb O2 and CO2, your lungs can pass some water into and out of your blood stream. This is not the ideal way to hydrate yourself, but it helps your lungs deal with small amounts of water, especially if it’s well distributed on the surfaces of your lungs. A thin layer gets absorbed quickly, similarly to how if you were to mist-spray a towel, it would dry easily, but if you squirt-sprayed a spot on the towel it would take longer to dry. The water can easily evaporate into the air AND dissolve into your blood and tissue.

6. Water droplets carry things. Water in lungs health concerns often carry the complications of other stuff in the water, like viruses, bacteria, parasites, and just plain debris. Water vapor is a gas, and it doesn’t carry bacteria and viruses the same way as droplets.

Last note, if you can see the “steam”, it’s not a vapor anymore. Water vapor is clear and colorless. If you see the steam cloud, it means that the water vapor is mixing with the cooler air and condensing microdroplets in the air, creating that white cloud. These are technically droplets, and can stick to your lungs. The reason you aren’t dying from it is because it’s a small enough amount of water that your body is able to manage for reasonable periods of time. Also, when water evaporates and re-condenses, it’s very pure and far less likely to be carrying contaminants.

Anonymous 0 Comments

This might weird you out to hear it. But the inside of you, all of you, is wet.
Your bones are wet, your lungs are wet, everything inside is wet!! So a little extra won’t do any major harm, your body will balance it out

Anonymous 0 Comments

Not sure if this has been mentioned as well, but our lungs literally NEED to be wet. Our air is humidified as we breathe it in. In terms of evolution, we ascended from water creatures not that long ago. That’s why our lungs are still ‘wet’ and the air humidified. To couple that, our eyes are so much worse than those who still remain in the water because technically, our eyes still haven’t gotten use to living out of the water.

Anonymous 0 Comments

I wonder this myself, as someone who vapes I’m always wondering how I’m able to breathe in that much water vapor and not have any significant problems due to the water vapor. I’m sure there are plenty of detrimental health problems from vaping in general, but the water vapor. I use to work at a factory and we would go behind our machine and hit it and hold it in, and nothing would be exhaled out visibly, so how does this work as well?

Anonymous 0 Comments

I just want to point out that if you were to inhale actual saturated steam (not water vapor), you would scald your mouth, throat, and lungs as saturated steam is 100C at atmospheric pressure (that’s 212 in freedom units).

Anonymous 0 Comments

Steam is invisible. It’s also above 100C boiling and breathing in steam would absolutely kill you.

Luckily, in the shower, you are breathing in water vapor.

Anonymous 0 Comments

At the level of steam in your shower, it’s not usually an issue, but there are places in the world where it is so humid and steamy that to enter the area you must wear a SCBA to prevent your lungs from filling with water and you drowning to death.

Anonymous 0 Comments

Anaesthesiologist here.

When you breathe normally, your body naturally saturates the air with water vapour, either while passing through the nose, mouth and throat, or while inside the lungs.

It does it so well that in fact we generally assume the room air to have become fully saturated with water vapour by the time it is inside the lung – we have an equation called alveolar gas equation which is used to calculate the proportion of various gases that end up at your alveoli (the millions of small gas exchange units inside the lung), in this equation we actually deduct the saturated water vapour pressure before we do any calculation for other gases due to this effect.

https://en.m.wikipedia.org/wiki/Alveolar_gas_equation

By the way: do you realise that “steam” is actually liquid water like fog, cloud etc; actual water vapour which is the gaseous state of H2O is invisible?