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What is Black Mold?

What is black mold - featured. Black mold spores on a white wall

Discovering black mold in your home can be worrying - here’s what you need to know

Humidity and damp can cause your home to become a breeding ground for black mold, but what exactly is it?

The appearance of any kind of mold in your household can cause you to feel uneasy, but if you’ve spotted black mold then you may have an extra level of concern. Many of us will have seen reports stating that black mold can cause health problems, so it’s natural to be worried – but is it actually dangerous?

In this simple explainer, we break down what black mold is, its causes, the risks – if any – and the best course of treatment. Read on for expert advice and tips on protecting your household from the frustratingly common problem of black mold.

What is black mold?

All mold is a form of fungi and, unfortunately, it can be common in homes. Dr Jie Zhao PhD, is a research scientist specializing in indoor environmental quality and Head of Delos Labs. He explains: “Mold is a microorganism that reproduces by releasing spores through the air, which then settle on indoor surfaces such as floors, ceilings and walls.”

The most common black molds are Cladosporium, Alternaria fungi and Stachybotrys chartarum – and if you suspect that any of these molds are present in your home, it’s important to act quickly. Tony Abate, certified mold inspector and vice president and chief technology officer at AtmosAir Solutions in Fairfield, Conn, says: “Black mold can cause serious health issues and property damage.”

What causes black mold?

Like all fungus, black mold loves dark, damp environments. According to Dr Zhao, “Mold is very common in poorly ventilated buildings that are too humid or damp. While mold spores can come from the mold already growing inside the space, they can also enter indoor environments from outdoors – through open windows, vents and heating and cooling systems, for example, or be carried in on shoes, clothes and by pets.”

In addition, extreme rainfall can cause flooding, which leaves basements vulnerable to mold growth, and leaks can cause damage – which again means that mold is likely to follow. Normal household behaviours such as cooking, bathing and drying laundry indoors can also contribute to humidity, which, if the property is poorly ventilated, can create the ideal conditions for mold to spore.

How do I know if I have black mold?

There are several indicators that your property may be experiencing black mold. First and foremost will be its smell; that tell-tale musty odor. You may not see evidence of mold, since it prefers to grow away from light sources, but if you see water staining then you should search for mold growth behind walls, under carpets and floorboards. If you do see black mold growing, it will appear as small black spots – which can spread to vast swathes if left unchecked.

Still not sure? Tony Abate says there’s a straightforward method to determine whether or not you’re dealing with black mold: “A simple test is to take a cotton swab and dip it in chlorine bleach and dab that black spot. If the spot quickly vanishes, it’s likely mold, not dirt or grease.” He adds, “Remember that mold doesn’t like airflow and light; if black spots are showing on the surface, the underside of the substrate will likely have a much larger mold infestation.”

Is black mold dangerous?

It can be. Living with chronic mold can compromise the integrity of a property and cause health issues, particularly for vulnerable groups of people. Babies, young children, people with respiratory problems and weakened immune systems are most at risk from the compromised air quality associated with mold being present.

“Mold and mold spores adversely impact indoor air quality and have been associated with a variety of negative health effects”, says Dr Zhao. “Exposure to mold and mildew are known asthma triggers and may also cause headaches, coughing, wheezing, shortness of breath, sinus congestion, sneezing, nasal congestion and sinusitis”, he continues. Note, too, that susceptible individuals, such as those with mold allergies or asthma may have more severe reactions. “Additionally, a study from Brown University has linked mold to depression”, he says.

How to treat black mold

Sadly, treating black mold isn’t always as straightforward as identifying it in the first place. Eric Bramlett, realtor and owner of Bramlett Residential real estate brokerage in Austin, Texas, has extensive experience in dealing with mold in real estate. He has the following advice: “If homeowners discover a minor bit of black mold growing, the best approach is to clean with a bleach solution while running fans. Proper protective gear such as masks and gloves should be worn.”

What is black mold. Hand in rubber glove sprays mold above window

This advice comes with a caution: “More than once, a small patch has turned into a major infestation the deeper we’ve dug”, he warns. If you’re seeing evidence of mold in carpets, walls and ceilings, it’s likely that you’ll need to enlist professional help.

Tony Abate agrees: “Many people make the mistake of thinking that by simply cleaning off these black spots, they will have taken care of the mold issue. The recommendation whenever mold is seen is total removal of the surface by a professional to prevent further growth and spread of allergenic spores.”

You should also utilise air purifiers to improve indoor air quality affected by mold, Dr Zhao advises. “Air purifiers with high removal efficiency filters are very effective in removing mold spores from the air”, he says.

It’s important to recognise their limitations, however. “They cannot remove mold from surfaces such as walls, floors or ceilings. Whether mold spores are originating from an existing mold problem or coming in from outside, using the right air purifier can capture and remove them from the air before the spores settle onto indoor surfaces.”

So, the main takeaway from all of the above is that finding the source of the mold is key; otherwise, it will keep coming back.

How to prevent black mold

Prevention is always better than cure when it comes to managing mold and the good news is, there are plenty of tactics you can employ to get ahead of the pesky spores.

  • Keep humidity low. Try not to dry laundry inside and limit steam escapes when cooking.
  • Keep windows moisture free by wiping off any condensation with a microfiber cloth.
  • Run a dehumidifier and fans to keep air circulating.
  • Ensure proper ventilation, particularly in kitchens and bathrooms.
  • Fix any leaks immediately.
  • Perform routine building checks, taking care to include attics and basements, cupboards and around plumbed areas.

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