MOLDY CARPETS FROM A SOUTH FLORIDA MOLD INSPECTOR
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Have you recently experienced allergic reactions in your home? Have you noticed widespread mold odors? Yet you have no visible mold. If so, the majority of the mold problem might be in the AC system, or hidden inside walls or behind other building materials. A nurse once told me “don’t look for zebras look for horses”. What that means is that the correct diagnosis or answer to a problem is most often the most obvious and common one. This concept is also known as Akums Razor and it is typically an affective way of solving problems. What does this have to do with mold and carpets? It is often the case that mold problems are growing on one of the largest and dirtiest pieces of building material in your home, and that is your carpet.
Mold spores, mold odors, and health complaints may originate in dirty carpets that have been wet. As an experienced South Florida mold inspector, I have noticed that in homes with dirty carpets the levels of several types of mold spores are often elevated in the air. Curvularia, Nigrospora, Pen / Asp, and Cladosporium are commonly elevated in homes with dirty carpets.
MOISTURE AND MOLDY CARPETS
Water or elevated humidity must always be involved for carpets to become moldy. Carpets that produce mold spores must have come in contact with some moisture source at one time or another.
FLOODING AND MOLDY CARPETS
It should come as no surprise to you that one of the most common moisture sources in moldy carpets is flooding. If a floor floods and the water is not removed immediately, a serious mold problem may occur. In cases of flooding professional water extraction is recommended. In such cases fans and dehumidifiers may dry the carpet before mold occurs. If the carpet cannot be dried quickly, then professional mold remediation may be needed.
CARPET CLEANING AND MOLDY CARPETS
It may come as a surprise that carpet cleaning is also one of the most common ways to cause mold in carpets. Ironically, wet carpet cleaning can do more harm than good in regard to microbial growth. The reason being is not primarily the wetting of the carpet, but the lack of complete drying after shampooing or steaming. Very often an entire home can smell very foul and musty after shampooing your carpet. Every time you shampoo your carpet, mold and bacteria can grow. As it dries the microbes go dormant. When it gets wet again, the growth starts all over from where it stopped the last time. So over time the problem gets worse and worse incrementally.
HUMIDITY AND MOLDY CARPETS
Often high humidity is the cause of mold in carpets. If the humidity is above 60%RH, surface mold may grow all over including on the carpet. Based on my personal experience, the property can be absolutely full of surface mold, and it will almost never be visible on the carpet. Even a dust sample from the carpet may not indicate a problem because the spores in the carpet dust sample may be masked by the abundance of dust and dirt in the sample. To prevent humidity mold in the carpet keep humidity below 60% RH.
DUST AND MOLDY CARPETS
Besides moisture, dust or dirt is also required.
On behalf of carpet manufacturers I must state that it is not the carpets themselves that are the problem. Most carpets are composed of inorganic plastic like materials. Thus, clean carpet fibers are a poor food source for mold. It is the dust and dirt in the carpet that provides a food source for mold. When dust in a carpet combines with moisture in a carpet you have what is needed to fuel mold growth. Vacuum your carpet regularly and use a vacuum that contains a HEPA filter, so the dust and spores do not end up in your air.
COMMON VISIBLE MOLD TYPES IN CARPET
Sometimes carpets provide a unique indoor fungal environment for some specific molds.
On some occasions the types of mold colonies in carpet can be different from what might grow on a nearby wall. I conducted one mold inspection in Miami where I found Nigrospora mold growing on an apartment carpet near a leaky window. And during another Miami mold inspection I found a visible colony of Curvularia mold growing on carpets in a leaky water heater closet. At another property I found Spegazzinia growing visibly on a carpet. In each case the colonies were dark black obvious growths. This was unusual because Curvularia, Nigrospora, and Spegazzinia do not often form obvious large visible colonies in homes. Usually, you just see the spores of these molds in the air samples and not on surface samples. But on the above carpets they were growing in the form of quite visible and heavy growth.
COMMON NON-VISIBLE MOLD TYPES IN CARPET
Pen Asp is also common in carpets, but this mold grows well not just in dirty wet carpets. It grows in many indoor environments. When Pen Asp is from humidity, it is often Penicillium chrysogenum. You may see powdery white or greenish Penicillium chrysogenum on dark clothes and dark furniture. You will not see it in carpets. It blends in well with carpets fibers so look for it on dark clothes in your closet. At other times many types of molds can grow on the bottom of your carpet, or on the tack strip or carpet padding under the carpet. You will only see these problems if the carpet is lifted.
Slime mold growing in mulch.
The most unusual thing I can remember finding growing in a carpet was encountered during a mold inspection in Lake Worth. I found slime mold growing on carpets. This was extremely unusual because slime mold almost always grows outdoors in mulch. I only found this mold growing indoors on time between 2003 to the time of this writing in 2025.
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1-888-381-6651.