I had never paid much attention to the humidity in my Silicon Valley house, but my allergist, who is treating me for a dust mite allergy, suggested using dehumidifiers in my bedroom and home office to keep humidity below 50 percent, making it harder for dust mites to reproduce. For those fortunate enough not to have to think about dust mites, they are microscopic spider-related creatures “that feed on dead human skin cells and thrive in warm, humid settings,” according to the American Lung Association. The ALA recommends keeping humidity below 50 percent, removing upholstered furniture and drapes where possible, using allergen-proof mattress and pillow covers, washing bedding weekly in hot water, and reducing clutter and stuffed animals where dust mites collect or washing them regularly.
Although it rarely feels tropical, Santa Clara County has moderate to high humidity, averaging around 70 percent in winter and 50 to 60 percent in summer. Dust mites thrive above 60 percent humidity, reproducing quickly and increasing allergen levels. Once humidity drops below 50 percent, reproduction slows. Below 45 percent, populations decline sharply, and sustained levels under 35 to 40 percent make survival difficult for them and easier for me.
Dust mite allergies are common. “Approximately 20 million people in the United States have a dust mite allergy,” according to Cleveland Clinic. A 2023 study cited by the National Library of Medicine found that 5 to 30 percent of the general population show sensitivity on skin tests. People with asthma are far more likely to be affected.
Smart dehumidifiers
To follow my allergist’s advice, I set out to find the right dehumidifier. To give myself more control, I focused on “smart” models with WiFi and apps that allow remote operation and scheduling, along with voice control through Amazon Alexa or Google Assistant. I tested devices from Midea, TCL, hOmeLabs and Frigidaire and ultimately bought the Frigidaire 22-Pint Portable Dehumidifier for the bedroom and the hOmeLabs 25 Pint model for my home office. I also removed the carpeting in my office and replaced it with laminate flooring.
Dehumidifier capacity is measured in pints removed per 24 hours, and the size you need depends on square footage and humidity. Home Depot suggests at least a 10-pint unit for 500 square feet or less, adding 4 pints for each additional 500 square feet. Add 10 pints in humid climates, 5 pints if multiple people use the room, another 5 for multiple windows or doors, and 5 more if a washer or dryer is nearby.
Because units come in standard sizes, you may end up buying one slightly larger than the formula suggests. That is generally fine. Extra capacity may slightly increase electricity use and noise levels but can improve efficiency because the unit removes moisture more quickly and may not need to run as long.
Dealing with the water they extract and the noise they emit
One lesson from testing was thinking through where the water goes after it’s extracted from the air. All the models had internal tanks, ranging from 0.8 gallons on the hOmeLabs unit to 3.2 gallons on the Midea Cube 20 Pint, which I tested but did not buy. The Cube’s design requires lifting the main unit off the tank before emptying it. When full, 3.2 gallons weighs about 27 pounds, not counting the tank itself, making it fairly heavy. All units I tested shut off automatically once the tank is full.
All the units also include a drain port and short hose to channel water to a floor drain or outside. I have not yet drilled through an exterior wall, wary of hitting wires or causing other damage, so for now I am using the built-in tanks.
That works reasonably well with the Frigidaire in my bedroom, whose 1.7-gallon tank lasts nearly two days. But the 0.8-gallon tank in my office fills at least once a day. My plan is to enlarge the hole left by a former Comcast coaxial cable since I upgraded to fiber, though I am waiting for help from someone more skilled in drilling holes through exterior walls.
Noise is another consideration, especially in a bedroom or in my case an office where I do radio, TV interviews and podcasts. Using the free NIOSH Sound Level Meter app, I measured the hOmeLabs unit at about 50 dB on low and the Frigidaire at about 46 dB, each from roughly five feet away.
The hOmeLabs is rated at 51 dB and the Frigidaire at 43 dB, but manufacturers measure under controlled conditions at closer distances. My readings likely include background noise and sound reflections, so they are not pure measurements of the machines alone.
When sleeping, the steady sound does not bother me. In fact, it can be soothing, like white noise. The real issue is the compressor cycling off and then kicking back on, which can be abrupt enough to wake you. To avoid that, we either turn the bedroom unit off at night or set it to continuous mode, so it runs at a low, steady speed.
These units all have built-in hygrometers to measure room humidity, but they take readings from the device itself, not from other parts of the room. To get a more complete picture, I bought several Govee digital hygrometer-thermometers for about $10 each. They display humidity on a small screen and in a companion app that tracks levels throughout the day.
Dehumidifiers aren’t glamorous appliances, but dust mites aren’t exactly welcome house guests. Keeping indoor humidity down helps keep those tiny intruders at bay and allows me to breathe more easily. The dehumidifiers I bought may be smart, but following my allergist’s advice is smarter still.
Larry Magid is a tech journalist and internet safety activist. Contact him at larry@larrymagid.com.
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