Types of Mold

How can you tell what types of mold are lurking unchecked in your homes? Molds are so tiny, measuring less than 5 microns but they number around 1000 species and some species can really be dangerous to one’s health. There are countries where a system to categorize molds according to their health hazards has been adapted. The following are the hazard classifications for  different types of mold:

  • Hazard Class A: Molds belonging to this group are directly affecting one’s health through risk of infection or toxicity. These molds can be present in homes and offices. Controlling and exterminating molds in these areas is imperative.
  • Hazard Class B: These are molds that result to allergic reactions over longer period of time.
  • Hazard Class C: Molds in this category are not health risk but they can damage structures. Even this type of mold needs to be rid of.

The common types of mold can be divided into two: the black mold and the non-black molds. Some people have misconstrued the color of molds as an indicator of its toxicity. Mold colors do not really tell how toxic they are. Black molds aren’t always toxic, and toxic molds aren’t always black.

Generally, however, the black color carries an impression of being toxic. In fact, three types of mold that are really toxic —  stachybotrys, memnoniella, and acremonium — are really black molds. They contain mycotoxins or substances produced by molds that cause diseases or allergies.


Stachybotrys (or Stachy) is is a toxic mold belonging to Class A that thrives on highly moist environment or water damaged objects. They appear as black, shiny and slippery. Stachybotrys breeds in very damp or humid environment and can survive and grow after 24 hours of continuous wet condition like slow plumbing leaks, shower or bathing spill or water leaking on walls.

  • Where It Grows: They grow in colonies on high cellulose materials like hay, straw, wicker including materials like ceiling walls and tiles, wallpapers, insulation backing, paper files, cardboard, jute, dust and wood.
  • Health Hazard: Stachybotryotoxicosis is a disease caused by the mycotoxins in the fungus Stachybotrys. It was first reported in Russia in 1940 and people complained of common symptoms such as dermatitis, pain and inflammation of the mucous membranes of the mouth and throat, a burning sensation of the nasal passages, tightness of the chest, cough, bloody rhinitis, fever, headache and fatigue. In the 1990s, it was also reported to have caused respiratory discomfort and the deaths of infants in Cleveland, Ohio.


Acremonium (also known as Cephalosporium) is a type of fungus growing outdoor and indoor and can be classified as Hazard Class B or C.

  • Where It Grows: Acremonium grows in very wet environment like damp soil and decomposing plants. In buildings, they can grow in thermal and fiberglass insulations for heating and cooling systems. Often acremonium molds can be found in carpet and mattress dust, gypsum board, wallpaper and dry walls. They can also be found in a house with leaking water, and damp basement walls.
  • Health Hazard: Three varieties of the Acremonium species have been found to cause infections to man: Acremonium falciforme, Acremonium kiliense, and Acremonium recifei. Mycetoma, or Madura foot (maduromycosis) is a fungal infection focused in one area of the body and is caused by Acremonium. Other effects of Acremonium are pulmonary infections and infections of the cornea in individuals with low immune systems. Some findings link Acremonium to arthritis, pneumonia, peritonitis, endocarditis, keratitis, meningitis, and osteomyelitis.


Memnoniells echinata grows in soil and is very much alike with stachybotrys. Both are usually found growing together. The Memnoniella mold when found indoor can be dangerous because its tiny size makes it easier to enter the bronchial lining.

  • Where It Grows: This wind-borne mold develops in damp and warm areas and on cellulose materials like paper, sheetrock, plasterboard, ceiling tiles and wood. However, the mold is easily eliminated when the area or moisture source becomes dried up.
  • Health Hazard: Memnoniella does not pose great threat to humans but people with asthma can seriously be irritated and those with low tolerance to common allergies. Common symptoms are throat irritation, eye and nose itchiness and rashes.

If you think that your homes are mold-free, think again. If you are buying a new house or renting an apartment for your family, inspect every nook for any sign of mold infestation. Talk with the homeowner if you see molds developing and ask what can be done with the mold problem. The best way to get rid of molds is to regularly clean and scrub with bleach solution where molds are likely to develop such as in the bathroom, sink and basements.

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