Last month, I took a road trip to North Carolina. The area had just experienced an extremely wet and rainy spring, and the Airbnb I was staying in had been unoccupied since Covid-19 halted almost all travel in March. When I unlocked the door, a putrid smell hit my nose immediately, like a wet beach towel left too long in a hot car. I was now sharing my rental house with some sort of mold.
The pandemic has forced all sorts of buildings to sit empty for long periods of time. As people venture back into their homes, schools, and offices again, they may also find an unwelcome surprise inside. The Centers for Disease Control and Prevention warns people who are reopening buildings to watch out for potential hazards like mold and Legionella pneumophila, the bacterium that causes Legionnaires’ disease. Greg Bukowski, CEO of the mold inspection and removal firm Moldman USA, says he’s seen an uptick in customers in the Chicago and St. Louis areas where his company is based. “Homes that have been unoccupied for months have a high likelihood of having water-intrusion issues and subsequent mold issues,” he says. Water intrusion can come from something like a roof or plumbing leak or high humidity as a result of leaving the air conditioning off.
This is not a new phenomenon, of course. Vacation homes and foreclosed properties often harbor mold. New construction techniques may be somewhat to blame: Because homes are now tightly sealed for energy conservation, they may be poorly ventilated and susceptible to issues like mold. Every year, some unlucky school districts return in August or September to find classrooms full of the stuff, says Jason Earle, the founder and CEO of 1-800-GOT-MOLD?, a mold inspection and removal firm based in the New York City area. Oftentimes, he says, maintenance staff shampoo the carpets at the end of the school year and then turn air conditioning units off to save on utility costs, inadvertently creating a perfect environment for mold to thrive.
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Fungi need moisture and food to grow. They will eat almost any organic substance, from cardboard and wood to ceiling tiles and upholstery. What I inhaled were the airborne byproducts of its metabolic processes, or what the US Environmental Protection Agency says are “microbial volatile organic compounds.” I personally prefer to call them fungi farts.
Aside from producing a nasty smell, exposure to mold can also cause unpleasant side effects for people who are sensitive to it, like stuffy nose, coughing, and sore throat. If you’re immunocompromised, you may be more vulnerable to these and other symptoms, says Naresh Magan, a professor of applied mycology at Cranfield University in England. For parents, the most serious issue to be concerned about is childhood asthma: A number of studies have found a link between mold exposure and the condition.
That doesn’t mean all mold is scary or harmful. Humans are constantly breathing in a plethora of different fungi and other microbes; usually they just don’t realize it. “There are thousands of mold spores in the air,” says Magan. If you wash a piece of fruit, for example, and then put the runoff water into a petri dish, “you will find loads of bacteria, yeasts, and filamentous molds,” he says. The world is really just a gigantic terrarium full of microscopic creatures ready to be inhaled. But if the concentration of mold spores in the air becomes too high, like inside a mold-contaminated building, it can cause an adverse health reaction.
If you return from quarantining at a loved one’s place to find that mold has turned your home into its home, it should be removed. While some companies will sell you testing kits to identify the exact species, the process is not necessary, according to the CDC. “The health effects of mold can be different for different people, so you cannot rely on sampling and culturing to know if you or a member of your family might become sick,” the agency’s website advises.
If the mold covers an area less than 10 square feet, you may be able to take care of it on your own. On hard surfaces, the CDC recommends using household cleaners or bleach and water to remove the mold, as a property manager at my Airbnb did. Soft items, like rugs, need to be thrown out. If the problem is larger, the CDC refers people to the EPA’s mold remediation guide designed for professionals.
If you’re thinking about hiring one, Bukowski says a lot depends on your comfort level doing a somewhat dirty job. “Safety should be the top priority. For example, a 4-square-foot problem in the attic should be handled by a pro, because attics are usually difficult, unsafe areas to work in,” he says. Professionals also come equipped with proper protective equipment you might not have on hand.
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If you smell that signature musty scent but don’t know where the mold is hiding, Earle says a regular flashlight can be your best friend. Check typically empty areas, like attics, crawl spaces, and basements. Even if the mold itself is not visible, you may see signs of its presence, like blistering paint, loose wall trim, staining, or discoloration around windows. It’s also a good idea to look out for any leaks or puddles of standing water—mold loves wetness.
To prevent the fungi from taking root in the first place, Earle says you should keep your home heated or cooled to temperatures comfortable for humans, even if you don’t plan to be there. “This is something we warn people about all the time: Buildings need to be lived in or maintained as such,” he says. But the most important thing is to control the level of moisture. The CDC recommends keeping humidity levels as low as possible, ideally below 50 percent. If you’re planning an extended absence, you can invest in a smart thermostat capable of delivering moisture readings, or simply have a friend or family member drop by once in a while to check on things.
Cleaning up mold is just one of many challenges communities are facing as they begin reopening offices and schools in the middle of a pandemic. More than half of US public schools are in need of repairs, according to a Government Accountability Office report released in June. The most commonly needed fixes are to heating, ventilation, and air conditioning systems—the very infrastructure necessary for stopping mold.