How To Get Rid Of Mold Spores In The Air

Mold Can Make Your Family Sick. Here's How to Get Rid of It.

The truth about black mold, fungus farts and that goop in the corner of your shower.

Credit... Andy Rementer

Published June 4, 2020 Updated June 5, 2020

When Mike moved from Vancouver to Silicon Valley in late 2018, he couldn't believe his luck. He found a beautiful Art Deco cottage less than 30 minutes from work, with redwood forests and wineries on its doorstep and rent that was inexplicably within his price range. It was the dream home he and his wife, Jackie, had been searching for — perfect for the family they were about to start.

If you feel like you're watching the opening of a horror movie, you're not wrong.

First, the heating got weird. "We'd turn it on and the whole house would suddenly fill up with this strange, humid, almost tropical warm air," said Mike, who asked that his last name be withheld to avoid retribution from his landlord. "Water would condense on the windows and just pour down the panes."

No amount of cleaning kept little blooms of mold from flowering on the walls and window frames. When Mike went down to the basement (disregarding decades of horror canon) he found that his heater was a 1940s-era contraption with rusted ducts, drawing air from earthen trenches flooded with stagnant water. They turned it off.

The problems stopped, and soon their son was born. Mike's landlord replaced the heating system and sealed up the old ducts and vents. But when the rains came back in November, the baby became sickly and wheezy. "He always had a snotty nose and this constant chest gurgle," Mike recalls. Their pediatrician dismissed concerns about mold, instead blaming day care. The respiratory problems grew worse and soon he needed an inhaler.

It was when he developed pneumonia that Mike's unease turned to dread. Was his dream house making his child sick?

It's coming up on mold season in many parts of the U.S., and with the ongoing pandemic and looming possibility of new outbreaks and quarantines you may feel a nagging worry about what could be hiding in your home. Terrifying tales of mold invasion abound on the internet — ones that spark many questions. How dangerous is it? Are some types worse than others? What can you do if your house has mold, and at what point should you just walk away?

It's hard to sort fact from fiction, especially when some of the misinformation is coming from the very people paid to exorcise mold demons for you. Luckily, there are things we can do for peace of mind while — like in any good horror flick — we're all trapped in our own homes.

First the good news: We are all constantly breathing in a "thick soup" of fungi, bacteria and other microbes, plus their byproducts, said Naresh Magan, D.Sc., a mycologist at Cranfield University in England. No, really, this is good news. It means our immune systems have adapted over 500 million years to cope with fungus.

For some, though, trouble at home starts in mold season, when warm, damp weather triggers mold to release its spores. Any kind of mold spore can colonize your living space, but there's a quartet of usual suspects: Penicillium, Cladosporium, Alternaria, and Aspergillus. Stachybotrys, the toxic so-called "black mold," is very unlikely to colonize your home.

Demystifying mold

Mold spores stick to surfaces and, if conditions are sufficiently warm, moist and undisturbed, extrude tendrils which turn almost any surface into food — these form the fuzzy structures creeping out of the corner of the shower. Ceiling tiles, wood, paint, rubber, carpet, soil, dust; it's all food to the mold, just add water.

How do you know when mold has arrived? That's easy: you'll smell the — how to put this? — the airborne end products of its digestive processes. That's right, mold farts. "Every time you smell that musty odor, that mold smell, that's what you're breathing in," said David Denning, principal investigator at the Manchester Fungal Infection Group and a professor at the University of Manchester, in England.

What effect does all this fungal activity have on health? Broadly speaking, we know there are two main ways mold can engage the immune system, and they depend on whether your system is underpowered or overactive.

If you're going through chemotherapy or have had a recent organ transplant, your evolved immune system firepower may have been depleted. The fungus can colonize the lungs and begin treating you as it would ceiling tiles or wood paneling, said Matthew Fisher, an epidemiologist at Imperial College London. But this is more often a problem in hospitals, home infections are exceedingly rare.

You're much more likely to have an overactive immune system that freaks out when confronted with the irritating proteins present in spores and mold filaments. Filaments land on the mucous membranes of our eyes, nose and mouth, causing eye-watering, itching, sneezing, coughing or asthma attacks.

For most, these stop when you leave the moldy room. But experts estimate that between 5 and 10 percent of the population are more sensitive than others. "In an environment that's colonized by fungus, you're also going to be inhaling those spores every day and you may potentially become sensitized to them," said Elaine Bignell, Ph.D., who co-directs the Manchester Fungal Infection Group.

Sensitization means your body recognizes a substance and mounts an aggressive response to even the faintest traces of it. If you already have asthma, you might get a particularly severe "fungal asthma."

More worryingly, a decade of studies show a firm link between mold exposure in infants and the development of asthma symptoms by age 3. The only thing more correlated with asthma onset is maternal smoking.

That's the settled science. Beyond that, things quickly get confusing, scary and unsupported. Various exploitative websites, remediators and clinics cite a handful of papers claiming links between mold and neurological damage and developmental delays in kids. Neither Magan nor Denning buy it. "There is not enough of a body of evidence to support this," said Denning. "This needs more in-depth investigations to prove cause and effect."

That is always the tricky bit. As with conditions like Wi-Fi sensitivity, symptoms of mold sensitization are all over the map, and tangled up with other potential allergies, like dust mites or cat dander. In particular, it's impossible to disambiguate whether someone is sensitive to fungal fragments, the spores themselves, or the volatile organic compounds in the mold farts.

Some people claim that they are sensitive to chemicals in these V.O.C.s, but when they were tested in placebo-controlled trials the results were mixed. When some participants were told that mold had been released (but hadn't) they would often manifest symptoms like debilitating headaches. When mold spores were actually released without telling them, they remained unaffected.

Denning has a lot of sympathy for people who live with these problems. "It's no doubt that these people are suffering," he said. "But as with a lot of things, the science isn't there yet to say it's actually mold that's the culprit."

The path of resistance

Initially, Mike's landlord tried to fix the problem himself, bleaching the moldy walls. "We call that 'spray 'n' pray'," said Scott Armour of the Institute of Inspection Cleaning and Restoration Certification, a global industry body for remediators. They, along with the EPA, advise against bleach for a variety of reasons, namely that fumes can be dangerous and it's usually ineffective.

Bleach only works for non-porous surfaces. It can't touch the mold that has burrowed into surfaces like wood or drywall (supposedly, vinegar may help you there). But the most important reason bleach fails is that people don't stop the mold's water supply.

"First thing I do is check for leaks, in the bathroom or roof or a crack in the foundation," said Greg Bukowski, who runs the Chicago-based remediation company Moldman USA. "There's always a leak." If you don't fix that, don't bother with bleach or vinegar. Then kill and remove the mold with detergent and water, then prevent its return with mold-resistant paint like Kilz (which, confusingly, does not kill existing mold).

When bleach didn't work, Mike paid for an indoor airborne mold test, which raised more questions than it answered. "We had no idea how to interpret the results. I just couldn't find any information out there that isn't written by remediation guys," he said. They told him he had the dreaded black mold, and needed professional remediation. (Even if your mold is that color, it's usually not the infamous toxic black mold. Unless the remediator has sequenced your mold's genome, don't take their word for it.)

Whatever kind of mold you have, if there's more than 10 square feet of it, the EPA advises against DIY remediation. But where do you find a specialist for larger areas? Denning said while the industry is not quite snake oil, it is certainly not based on settled science, and it is being sold by an under-regulated industry.

Reputable remediators wanted

Bukowski is the first to agree. "We don't have the greatest reputation as an industry," he said. "There's a lot of scare tactics, and they leverage that to charge really high prices."

For instance, the mold test Mike paid for was likely not useful. "There are so many reasons not to do a home test of any kind," said Armour. "No home test is reliable. None are valid."

Still, after the mold test results, Mike and his family moved into an AirBnB for two weeks. They were worried about the baby developing asthma — whether from the mold or from the "mold fog" Mike's landlord hired remediators to set loose. Mold fog is similar to roach bombs and their efficacy is just as contested.

Not everyone in the industry is trying to upsell people's misfortune. I.I.C.R.C. is a good place to find reputable mold remediators, and is working to establish standards, guidelines and training around how to deal with the problem.

Regardless of who performs the exorcism — you or a reputable specialist — after it's complete, your work is not done. Some firms offer long warranties, but you need to do your part. Some people will have a harder time than others. If the ambient humidity in your area is above 80 percent, congratulations, it's always mold season.

Your situation is probably worse if your home is made of wood. (Brick houses anecdotally offer less nourishment for mold, but no official studies confirm this "Three Little Pigs" system.) In mild weather, get a dehumidifier to keep your home under 65 percent humidity, which prevents most molds from gaining a foothold. As the temperature outside drops, however, a complicated relationship emerges between temperature and indoor humidity, often causing the mold-bearing condensation Mike saw in his home.

The rule of thumb is to drop the humidity by 5 percent for each 10 degree drop outside, and regularly drain the water from the dehumidifier and clean it. Track any leaks and cracks in your home and always change your air conditioning filters on schedule.

And if you do have a mold allergy? Pay attention to the age of your bedding. I regret to inform you that the mites who live in your pillow poop there, which makes a tasty snack for mold. Your head sweats on the poop and the mold while you sleep, and then it grows.

Mike didn't have to worry about the dehumidifier — this past February was the driest in California on record. Eventually, antibiotics and an inhaler cleared up the baby's pneumonia. Nonetheless, just before the Covid-19 lockdown, he and Jackie decided to abandon their dream home. Apart from tearing the whole house apart, there was no way to know if hidden pockets of mold lurked behind the walls, and their landlord was tired of doing tests.

"We just didn't want to wait and see what the house would do to our son next year," he said. Their new place is smaller, more expensive and free of unwanted guests. For now.