Fungal Library 

What Is Mold?

There are thousands of known mold and fungal species types. There are too many to list here, but the majority are harmless to humans, some are even good for us. There are a few species, however, that can be dangerous if allowed to grow in an enclosed dwelling.

The mold and Fungal spore types below are examples of the most frequently found species. We have provided some basic information on each to help you understand the characteristics of the most common indoor molds.

Fungal Types We Are Most Concerned About

The Three Main Types of Harmful Molds Are:

  • Chaetomium
  • Smuts
  • Rusts

These are the three most dangerous types of molds to humans. The following is a breakdown of each of the three types. If these harmful fungal types are not remediated, they can lead to serious health risks.

Our Fungal Library lists the most dangerous types of mold and Fungal species. Knowlege is power! Knowing the type of fungal species you are dealing with will help you decide what steps to take next.



Chaetomium is a genus of molds. It is a dark-walled fungus normally found in soil, air, and plant debris. Chaetomium is a contaminant and a causative agent of infections in humans. A few cases of fatal deep infections due to Chaetomium atrobrunneum have been reported in the immune-compromised host. Other clinical syndromes include brain abscess, peritonitis, and onychomycosis. Chaetomium infections in humans can be avoided by proper hygiene habits. A little known fact is that showering with soap after working out in a community gymnasium will help reduce the chance for infection.



Smuts is a member of the Basidiomycetes family and has two spore types: teliospores (dry, powdery stage) and basidiospores (yeast stage). Smuts do not usually grow indoors. They are parasitic plant pathogens that require a living host for the completion of their life cycle. There are no reports of human infection by the plant parasitic forms. The identification of smuts on a mold analysis report often indicates a landscaping issue at the foundation of the building.



Many of these species are plant parasites. Some are superficially similar to the smuts, although their relation to each other is not clear. They most commonly reproduce via asexual spore production. Their spores are airborne and can travel great distances. They mostly cause foliar infections. The group received its common name from the fact that some species have a reddish spore stage which resembles the corrosion process known as rust.