Why humidify?
Among the many things I wish I’d never had to learn, but did, because of COVID, is the term “mucociliary clearance”. And, hand-in-hand with that, I now understand that the standard advice to “drink plenty of fluids” when you have a cold has nothing to do with your kidneys. That’s actually for the health of your lungs.
Your entire upper respiratory tract is lined with mucous membranes, and in addition much of the surface is lined with little hairs (cilia). Mucous itself has substances that fight pathogens, and the cilia sweep the mucous toward the top of your throat, where you (ahem) eliminate that mucous in some fashion.
This is the primary mechanism by which your lungs protect and clean themselves. Of anything that lands on the surface of the lungs. Mucous traps things before they can actually get to your lung cells. And then your lungs continuously sweep the mucous lining up toward your throat, where it gets disposed of.
And so, the whole point of “drink plenty of fluids” is to keep your mucous loose, per WebMD.
To today’s point, dry air inhibits mucociliary clearance, and humid air increases it. (Also referenced halfway through this review article.) And it’s not exactly rocket science to understand it: Dry air dries out your mucous. That slows down the rate of transport. And so your entire upper respiratory tract functions less well at cleaning itself, and protecting itself from pathogens.
That’s why four out of five HVAC engineers agree: Keep your indoor relative humidity between 40% and 60%. That recommendation is based, in part, on studies like this one, of mice and flu, literally out of the American Society of Heating, Refrigeration, and Air conditioning Engineers (ASHRAE) handbook:
Source: ASHRAE.
See Post #894 for other studies, including ones using guinea pigs, and ones effectively using school children as guinea pigs.
With this latest bout of cold weather, the relative humidity in my house has finally fallen to 40%. So I’m firing up my first humidifier today.
After having tried many different types of humidifiers over the years, I’ve decided that I hate them all (Post #895). Noisy, dusty, stinky, and/or expensive. Take your pick. I have grudgingly settled on a pad-type humidifier with removable tanks as the least-hassle approach to maintaining indoor humidity.
I’ll be toting 2-gallon jugs of water for the next few months, keeping that filled.
All that, just to keep up my mucociliary clearance.
