Most conversations about indoor air quality focus on pollutants, like toxic chemicals off-gassing from paint or pressed wood in furniture and cabinets or emanating from air fresheners and cleaning products. But how humid our indoor air is can affect our family’s health, too, especially in winter. Why does “relative humidity” matter and how can you make sure it’s adequate inside your home?
“Relative humidity” is the percentage of the amount of water in the air RELATIVE to the maximum the air can hold at a given temperature,” explains Treehugger. Like Goldilocks in the fairy tale, you don’t want too much, or too little. In winter, many of our homes have too little – maybe 20% or so. What’s “just right” is in the 30-50% range, says the Mayo Clinic.
One way to visualize this is to consider how a sponge works, say these health professors. “At 100 percent, the sponge is totally soaked; at 50 percent, it holds half as much water.” The more you wring out the sponge, the drier it gets.
Dry indoor air is connected to an increase in infections for a few reasons. One is that the mucous membranes inside our noses and throats help capture air-borne virus particles. But when that air is too dry, our bodies create less mucous so fewer virus particles are being trapped.
Also, when the air is too dry, tiny virus particles can travel farther across a room, increasing the chances they’ll be inhaled.
Drier air can also lead to more sore throats, dry skin, nosebleeds, and dehydration. My own children had a tendency to develop random nosebleeds and wake up with sore throats until I put humidifiers in their rooms during the cold winter months. This tracks with one study conducted in a pre-school that showed when classroom humidity was maintained at about RH 40%, there were fewer infectious droplets in the air and that fewer children missed school.
While it makes sense to keep an eye on your home’s relatively humidity generally, it makes particular sense during the coronavirus epidemic. Not only is the virus highly contagious, but we’re spending more time inside our homes than ever before. That’s worrisome because research indicates that Covid survives longer, is more likely to spread in colder temperatures, and there’s a higher chance of infection when indoor humidity is low.
Wondering what your home’s relative humidity is? The smart thermostat on my HVAC system gives me an automatic reading right next to the current temperature of the house. If your thermostat doesn’t provide similar information, Mayo Clinic suggests getting a hygrometer from your local hardware store or online. It is a device that looks a little like a thermometer, but measures the amount of moisture in the air, rather than the air’s temperature.
If you need to add moisture to your home, choose a humidifier carefully. In some cases, you can add a humidifier to your furnace. If you decide to buy a humidifier, choose a model that is easy to clean. Dirty water “reservoirs” and filters can breed bacteria and mold; you don’t want to replace one problem with another.
Medline Plus, of the National Institutes of Health, says, “Always use a cool-mist humidifier (vaporizer), especially for children” to avoid burns. Place the humidifier several feet away from the bed so kids won’t run into it in the middle of the night. Use distilled water rather than tap water, as tap water contains minerals that can collect in the unit and get released into the air as dust that can cause breathing problems.
Keep in mind that humidity levels that are too high could lead to mold and mildew build-up, so be on the lookout for room surfaces that become damp or wet to the touch.
So, take a deep breath and aim for a relative humidity level of 30-50% overall.
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