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A Comprehensive Guide to Mold

Mold is a common problem, especially in areas with high humidity. Ignoring it is never a good idea, because it spreads quickly and it is harder to remove once it gets everywhere. Mold spores travel through the air so once an infestation begins, if left untreated, the problem becomes worse. Many infestations are not visible. Mold hides in walls, crawlspaces, under damp carpets, in water-damaged wood, and even in duct systems.

What is mold?

Molds are fungi. Fungi are unique because they do not need light to survive. Unlike plants, which use photosynthesis to convert light into energy, fungi directly consume a food source and do not need sunlight. One of the largest living organisms on Earth is a fungus discovered in 1998 in Oregon. It is mostly underground and covers an area of more than four square miles. That is 1,665 times the size of a football field. It is also over two thousand years old. Fungi are very strong, and if undisturbed live a long time.

Molds are the smaller cousins of this gigantic fungus. They thrive anywhere they find a food source and moisture. They like to eat all kinds of things, including paint, wallboard, wood, paper, plaster, carpet, and almost any kind of waste. Light does not affect them, but they do not need it either. This is why mold also appears in shower stalls and around bathtubs. They need moisture. They are voracious eaters of many things. They even eat caulking and tile grout. There are several types of mold, but all of them thrive in dark, damp, places like under the sink or in between water-damaged walls.

How does mold occur?

Humid, dark environments are the perfect breeding ground for mold. Leaky roofs and plumbing problems are major causes of mold infestation in the home, especially the troublesome kind of infestation, which is impossible to see. It is the hidden mold that is often the most dangerous, like when the mold spores circulate through the home or apartment HVAC system.

What are the dangers of mold?

Molds are almost all unwanted, and many are dangerous. The reason for concern is that molds replicate by producing spores. Spores, by their nature, are meant to be carried by air currents so the mold can propagate. These spores are very tiny. They fly around in the air to find new locations for a colony of mold to begin. It is very common for people to have allergic reactions to these mold spores. When they are inside the home, in a musty environment, the problem amplifies. There are no molds considered completely safe. When it is present in the home, it is important to take appropriate steps to remedy the problem, so the occupants do not suffer harm. In addition to allergic reactions, the other problem is many molds produce toxic substances called “mycotoxins.”

What are the common types of mold?

These are the common types of toxic mold and some places they like to grow:

  • Acremonium – This mold makes a toxic substance, dangerous especially to children if eaten.
  • Alternaria – This toxic mold is commonly found inside. It lives in carpets, on curtains, and on windowsills.
  • Aspergillis – This mold grows on damp carpets or water-damaged wood and in the glue used for wallpaper.
  • Chaetomium – This mold likes to eat cellulose, so its favorite places are anything made of paper or cardboard. It also grows between layers of plywood if it is wet, and in carpets.
  • Cladosporium – This mold likes to live in the ducting of a home.
  • Fusarium – This mold makes its home in humidifiers.
  • Paelimyces – This mold lives in dirt and dust in the air.
  • Penicillium – Found in carpet, wallpaper, paint, compost, and in fiberglass insulation.
  • Stachybotrys – This mold likes damp wood, drywall, and ceiling tiles.
  • Trichoderma – Produces a toxic antibiotic. It is found in paper.

What are the symptoms of toxic mold exposure?

The symptoms vary from person to person due to their sensitivity. Asthma is a national epidemic in the United States, and mold is a known trigger of asthma attacks. Upper respiratory distress of other kinds is also very common. These include watery eyes, coughing, runny noses, and sneezing. Allergic reaction to molds often appears to have similar symptoms of flu. Dizziness, fever, and headaches are also possible.

Where is mold found in apartments and houses?

A tiny drip under the sink will, over time, produce plenty of trapped moisture to start a colony of mold growth. Any kind of water damage from a hole in the roof to weather storms is enough to get mold started. Poor ventilation is another culprit. Warm moist air, trapped in the attic, or between walls, creates a perfect environment for mold to grow. Condensation of water behind and under refrigerators or freezers is another likely location. Air conditioning systems are almost automatic mold generators because the heat exchanged between warm air to make it cooler results in water accumulation. The water tray under an air conditioner is almost certain to have mold, as well as any filters that are not cleaned or well maintained.

Delaying maintenance or cutting back on necessary repairs only makes matters worse. Once mold gets a foothold in any apartment or home, getting rid of it becomes increasingly more difficult after giving it time to grow.

How do mold specialists test for mold?

Professionals test for mold by conducting a thorough visible inspection of the premises, looking for areas known to have mold problems. They consult with homeowners for any history of water damage and check for any sign of plumbing problems. They inspect spaces normally hidden from view such as HVAC systems, under the home, under stairs and in the attic, basement, or crawlspaces. They look under carpeting and test drywall. Each home or apartment is different and requires a professional who knows how to find both visible and hidden mold.


  1. Strange but True: The Largest Organism on Earth Is a Fungus
  2. A Brief Guide to Mold, Moisture, and Your Home
  3. Mold and Moisture
  4. A Brief Guide to Mold
  5. Mold Sampling as Part of a Home Inspection
  6. Get Rid of Mold
  7. Molds
70% of homes are estimated to have mold behind walls. (Harvard EDU)

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