Black mold: testing, facts, and background

Sep 11, 2020

The words “toxic black mold” could strike fear in the heart of any renter, homeowner, or contractor. At one point or another, almost everyone has heard a horror story, read a headline, or watched a talk show about the negative health impacts of the infamous “toxic black mold”. At Indoor Science, we frequently get requests for a black mold test — but what does that phrase really mean?


As discussed in a previous blog on water-damaged buildings, the term “toxic black mold” is commonly used to refer to Stachybotrys ( The CDC website explains that Stachybotrys is a greenish-black mold that grows under constant-moisture conditions. Stachybotrys is a mold that can produce mycotoxins as it grows. There are over 70 different species of Stachybotrys, but Stachybotrys chartarum is the species most linked to indoor health problems (
So there we have it — visually check your home and if you don’t see any black growth, you’re safe, right? Wrong!

Toxic black mold: Let’s break this phrase down

What is meant by the term “toxic”? Don’t worry, our blog has already covered the topic of mycotoxins. A mycotoxin is “a chemical compound that is synthesized by fungi that are toxigenic”. Several different types of mold can produce mycotoxins, but just because a certain type of mold can produce mycotoxins does not mean that it always will. Some types of mold can produce several different toxins, while some mycotoxins can be produced by several different types of molds. A more scientific term to use is “toxigenic mold”.
Using the term “toxic black mold” to reference Stachybotrys is actually quite misleading, as many different types of mold can appear black in color: Alternaria, Aspergillus niger, Chaetomium, Pithomycetes, Ulocladium, Nigrospora, Cladosporium, or Aureobasidium, just to name a few! Add in fact, not all black molds are toxigenic! For instance, Aureobasidium can appear black but is not considered toxigenic. And even Stachybotrys may appear to be dark brown rather than black! Now mold problems aren’t looking so clear-cut. Visually, we can not distinguish if black mold growth is Stachybotrys or any other type of mold without collecting laboratory samples.

All of these intricacies can quickly get confusing to the average person, so it’s important to remember the big picture: regardless of color, mold is a problem when growing indoors on building materials. Whether green, white, orange, or black, mold growth should be removed and the moisture source should be addressed to prevent it from growing back. Despite the mainstream attention it generates, “black mold” is not the only hazardous fungi.

So, do I need a black mold test?

Clients calling and requesting a “black mold test” are on the right track — If you are concerned there is potential mold, of any color, growing at your property, the best thing to do is get a thorough mold inspection to address the root cause.

At Indoor Science, we have several sampling options at our disposal and can perform various types of inspections depending on a client’s particular needs or interests. Most commonly we perform a thorough visual and moisture inspection of the property and collect samples depending on the project. This moisture analysis with an infrared camera, moisture meter, and thermohygrometer allows us to make recommendations for repair or remediation, which requires addressing the underlying source of the mold problem: moisture. Air and surface sampling can identify molds down to the genus level to let you know whether or not toxigenic molds are present. If mold is found in your home, the same standards and remediation methods are used to address all molds: those toxigenic and not.

The next time you think you might need a black mold test, or any mold testing for that matter, call us at 312-920-9393 to get a quote over the phone.