A Accredited Inspection Service Inc.

1-888-381-6651

Print this page

Eight Common Indoor Molds

 

The following information is from A Accredited Mold Inspection Service, Inc. It is based on 7 years of mold inspection experience and mold testing in Palm Beach, Miami - Dade, and Broward counties. The information is also based on our non-viable analysis of thousands of mold samples obtained during such inspections as well as the non-viable and viable analysis of samples being conducted by various labratories that we have used. 
A Accredited can be reached at 1-888-381-6651.  

Mold growth forms a stain-like or powder-like appearance on the interior walls of homes.  Its growth is caused by elevated humidity in the surrounding air or by moisture from water leaks in the surrounding environment. Many mold colonies start out as tiny round specks growing into circles. This is very true in laboratory growths of mold, but in homes mold growth is not as regular and uniform in shape for very long.  As mold growth progresses on your walls, the colonies may become confluent--that is to say, they merge into one another and thus do not appear as distinct circles any longer.  As it grows, mold may appear as irregular blotches of powdery residue or discoloring stains on water damaged surfaces.  Molds are not all black or green; molds come in many colors and forms. Below are descriptions of some of the more common household molds that home owners and inspectors are likely to find after moisture or humidity problems occur. This information is based on field experience gained by a certified mold inspector while inspecting mold problems in water damaged homes and commercial buildings for seven years, and while identifying mold spores under 1000X magnification using an oil immersion compound microscope for five years.
It is important to remember that visual observations provide only preliminary id of molds and that a trained mold spore analyst should always analyze samples under the microscope if the ID of the mold is to be known. Often mold spores exist in large numbers in the air, and only microscopic examination can confirm their presence.  
  
Penicillium and Aspergillus,collectively known as Pen / Asp, are the two most common genera or groups of mold encountered in homes and outdoors. Each genera or group has roughly 200 known species. Thus we know of about 400 species of Pen / Asp. Many types of Penicillium and Aspergillus such as Aspergillus versicolor come in a variety of colors and are not always green molds.  Many other species are black, including but not limited to Aspergillus niger. This form of Aspergillius is hydrophilic, which means it loves very wet conditions and as a result is only found on severely water-damaged surfaces. It loves water-damaged drywall, where it often forms colonies about the size of a coin. As time goes on, the round colonies may merge together. This mold grows in very similar habitats as Stachybotrys, also known as toxic black mold, and forms similar looking colonies to Stachybotrys or toxic black mold. Thus it is sometimes not different in appearance from it. This fungus is dark black on walls, but under the microscope, its spores are brown and look identical to sea urchin shells without the spines.  Aspergillus niger is used in the production of citric acid for sodas, but health issues can result when this fungi grows indoors. 
 
Some very common slow growing Golden Tan Aspergillus colonies are found in homes with borderline elevated humidity of around 60% or 65% RH. They do not require as much humidity as some other molds; thus it is a xerophilic fungus, meaning it is more tolerant of relatively dry conditions than other molds. It loves painted wood surfaces and is common in humid garages, closets, and cabinets. It also loves curtains and lamp shades near drafty sliding glass doors that let in too much humid air from outdoors. I have personally seen it hundreds of times, always in the above circumstances and never around leaks. It grows as very tiny golden tan spots. This mold does not produce much mold odor and is sometimes difficult to sample because it sticks tightly to surfaces and does not readily give up spores and hyphal fragments (pieces of mold fiber). Even when sampled with sticky adhesive sampling tape, it often does not cooperate.  It is important to take this into consideration because often this mold is likely mistaken for not being mold by inspectors, because sampling it sometimes gives mold inspectors false negative results with labs reporting no spores found. Press too soft with adhesive and you get no sample; press too hard and you get wall paint. 
  
White Aspergillus colonies growing on clothes and leather objects in humid closets appear as small white spots a few millimeters across. This is often called mildew by Realtors or anyone who does not want to call it what it really is, in reality it is mold. Lab analysis will identify it as Pen Asp from an air sample. A surface sample of the actual mold sent to the lab may bring back a more specific identification of Aspergillus, and a DNA analysis or culture analysis with speciation will often identify these white spots on your clothes as Aspergillus chrysogenum.  According to Wikipedia "Penicillium chrysogenum was discovered, on a cantaloupe from a grocery store in Peoria, Illinois. The fungus isolated from this cantaloupe produced several hundred times as much penicillin as Flemming's original cultures of Penicillium Notatium." The inventor or penicillin antibiotic Alexander Fleming first discovered it in a petri dish in his lab. According to microbewiki " Penicillium chrysogenum produces glucose oxidase, which is used as a preservative in fruit juices."
In the lab it is often green, in water damaged homes it is often green, it is often white when growing in humid environments. This is not surprising because I have observed other molds to appear different depending on the environment they are in. This fungus is an extremely common mold in humid environments. Its spores are sometimes found in water-damaged buildings as well.  After months or years of growth the round colonies merge to become like sheets of powdery white dust. The spores resemble echinate or (rough spiny) pineapples under the microscope.  Some old timers would call this mildew and brush it off clothes, shoes, and belts; the problem is that it keeps coming back. This is not mildew at all; true mildew grows on food crops. This is a type of Aspergillus mold that is associated with mold odor, allergy, and asthma problems. About once each year I find a client who complains of allergic fungal dermatitis or itching rashes caused by allergens, and the client’s doctors have confirmed this to be allergic dermatitis in more than one case. It is interesting that in every case this so-called white mildew is growing on the clothes that contact the itchy skin of persons suffering from allergic fungal dermatitis.  The clients wear the moldy clothes because they sometimes do not notice the small white spots on the white clothes; they only see it on the black clothes.  

    
Chaetomium is commonly found on heavily wetted water damaged building materials. Chaetomium, a fairly common mold, is often brown and grainy in appearance and looks like cinnamon. Peel back a water-damaged baseboard or moldy wallpaper and you may find it hiding there. Its spores look like nice-sized tan or brown lemons under the microscope. A tape sample of Chaetomium mold reveals that the mold spores are packaged by the dozens or hundreds inside round tangled masses of what looks like bristly hair balls impregnated with the lemon shaped spores. In fact, the name Chaetomium means bristly. These hairy spore-forming containers are called cleistotheca. Sometimes mold that resembles Chaetomium is Pen / Asp, with the grains being masses of spores in conidiophores or, rarely, in structures more similar to those hairy masses produced by Chaetomium (cleistotheca or peritheca). However, in most cases the really grainy stuff is actually Chaetomium.  

Cladosporium
is extremely common; it is a non-toxic black mold that causes allergic reactions and asthma reactions. Cladosporium forms tiny black spots or irregular shapes; it loves to grow around condensation as well as water damage. If you see black spots on a hard surface with condensation, then chances are it is Cladosporium. The two most common types in homes are Cladosporium cladosporioides and Cladosporium sphaerospermum.
Cladosporium cladosporioides looks under the microscope like clear colorless prickly pear cactus without the thorns; it is amazing that something clear under the microscope is so dark black when growing on your AC register.  Cladosporium sphaerospermum looks like tan irregular shaped sesame seeds, sometimes with lobes. A cell nucleus is often visible in the one-celled spores. Both common forms of Cladosporium are very common on AC registers, in and on AC ducts, on shower walls and shower ceilings and under wall paper. However Cladosporium sphaerospermum that is indistinguishable from Cladosporioides on the above referenced surfaces appears very different on AC coils and blower fans. In such cold breezy environments it looks like grey velvet. 
 
Stachybotrys, also known as black mold, toxic mold, or toxic black mold, is dark black. It produces toxic compounds. Some books and even Wikipedia report that Stachybotrys or toxic black mold is sometimes greenish black. Based on this inspector's personal observation of this mold in many houses, the greenish black variety is extremely rare. In addition, microscopic examination of greenish black Stachybotrys has always so far revealed that the greenish Stachybotrys is not at all green. The greenish color always comes from other fungi such as green Penicillium or Aspergillus growing intermingled with the Stachybotrys growth.  It would be very strange for this toxic black mold to be green because its spores are always very dark black under the microscope and never green. The spores look like rat droppings.
 
Fast-growing fluffy Mucor is not a common house mold, but is included in this article because you may encounter it on food at some time or another. It sometimes invades lab Petri dishes, where it out-competes other molds in the dish, thus making it difficult or impossible for lab personnel to identify other molds that may be attempting to grow in the same Petri dish sample. This mold may be found on old bread or rotten fruit where the only consequence is the loss of a small amount of food.  The same Mucor mold may grow in the sinuses of immuno-compromised people; it does not appear to infect people with a normal immune system.  In 2009 one of our mold inspection clients was infected with this mold and the doctor prescribed a common looking small container of antibiotics that caused her $1000.00. When she asked if she needed to take the exorbitantly priced medication, the doctor replied,  "Only if you want to live." This potentially infectious mold is a vibrant white and fluffy in appearance.
 
Most molds produce spores and mold odors; regardless of the type of mold many persons experience various health problems when exposed to fungal spores and fungal odors.  If not treated at the right time, it can cause a lot of lung-related problems and breathing hindrances. It can trigger allergies and give rise to sneezing, asthma or cold-like symptoms in people.
Regardless of the type of growth you have, it should be treated the same way.
Repair the leak or humidity problem and have a mold remediator remove the moldy building materials in a way that complies with nationally acceptable mold removal guidelines designed to keep the mold from spreading through the air during removal.
In most cases it is best to have a mold inspection done by a certified mold inspector so that inspections and testing can help diagnose the root cause of the problem. Without first understanding and addressing the root cause of the problem, the mold growth will likely return after remediation.