Cleaning moldy carpet. Despite the prevalence of mold growth on carpet as part of restoration projects, there is little definitive information available on proper procedures for addressing it. (Photo: Shutterstock)

While professionals who specialize in remediation and restoration of damaged buildings have seen the growth of hard flooring over the past decade, carpet still makes up an extremely large portion of floor finishes. Some flooring experts estimate that as much as 10 billion ft. of carpet is being added to the U.S. building stock on an annual basis.

Considering that water losses are by far the largest type of insurance claim filed in the United States (almost 50% of claims as compared to less than 5% of claims for fire damage), it is no wonder that mold growth on carpets is a common challenge faced by individuals who are responding to emergencies.

A variety of opinions

Despite the prevalence of mold growth on carpet as part of restoration projects, very little definitive information is available on proper procedures for dealing with such situations. While the internet is full of suggested cleaning methodologies, restoration professionals are held to a higher standard than do-it-yourselfers as they are tasked with returning the building to a pre-loss condition. In many areas of the country, this has led to a general mindset that carpet with visible mold growth should be treated as a porous material to be removed and replaced, rather than a material that can be cleaned.

The basis for the default approach, in which carpet with visible mold should be replaced rather than remediated, comes from the idea that because carpet holds water, it is a porous material (as described by a number of documents, which contribute to the industry standard of care).

Many individuals who hold this view focus on the section of the S520 Standard for Professional Mold Remediation put out by the Institute of Inspection Cleaning and Restoration Certification (IICRC) that describes porous material as… items that easily absorb or adsorb moisture and, if organic, can easily support fungal growth (section

This same guidance document then goes on to state that: Porous contents with “Condition 3” contamination is usually unrestorable based on material composition. The definition section in this document essentially states that any surface with visible fungal growth is “Condition 3”. Therefore, many restoration professionals automatically classify carpet with mold as a “Condition 3” porous material.

This thinking leads the mold remediation contractor to treat carpet with mold contamination in a fashion similar to a cardboard box or ceiling tile which has visible growth; tear it out and replace it. While this assessment makes the response process pretty simple, it does lead to the replacement of materials which could otherwise be remediated, rather than replaced.

A different approach as to how carpet with visible mold growth should be treated is found in the EPA document entitled: Mold Remediation in Schools and Commercial Buildings. Recommendations for the proper treatment of moldy carpet from this government organization are much broader with their advice ranging from the use of a wet vacuum, vacuuming with a machine equipped with a high-efficiency particulate air (HEPA) filter, or discarding the carpet.

One of the key considerations when looking at the more restrictive approach of the IICRC is while carpet does absorb moisture because of its construction, very few carpeting materials today contain organic constituents such as wool, cotton or silk. As such, there is no industry document that prevents the cleaning of most commercial grade carpet with visible mold contamination as long as the fungal growth is actually removed.

Still, removal of mold from carpet can be tricky. One reason for the hesitancy in cleaning such carpet is the fear that leaving microscopic spores behind will lead to future growth. Another common concern of the restoration professional is the way the mold grows, which pushes them to favor removal and replacement of carpet rather than cleaning.

Although fungal organisms do not have roots, they do produce hyphae (filaments that act like plant roots to secure the colony to the surface). When mold grows on carpet, it does result in some of the hyphae wrapping around the individual fiber strands of the floor covering. This intertwining means that physical action/agitation alone, like vacuuming, is unlikely to separate all of the fungal filaments from the carpet fibers.

With all this in mind, the focus in claims with mold on carpet should focus on two key aspects: 1) proper evaluation; 2) proper implementation when cleaning is appropriate. The evaluation of the carpet is straightforward in that many methods can be used to ensure no organic materials such as wool or cotton are components of the carpet which is impacted by mold.

If the evaluation indicates the carpet is an acceptable candidate for cleaning, then choosing the correct process is critical. Choose one that will remove the mold and restore the carpet to a pre-loss condition without damage; such as shrinking, fading or bleaching.

Treating mold on carpet

If the insurance industry is going to be successful in changing the default mindset of replacing carpet with mold growth, it is critical to make sure that any cleaning efforts actually remove all of the fungal materials; not just the fungal parts visible above the surface.

Both science and practical experience provide the answers, which allow carpets with mold to be cleaned. Moving away from a one-step approach to a multi-part process means that both physical agitation and proper chemistry can be utilized to attack the mold in different ways in order to facilitate its complete removal.

Whether it is carpet or other surfaces, twenty years of experience with mold remediation have taught professionals that a thorough vacuuming is the first step in effective mold removal. When dealing with moldy carpet, a HEPA-filtered vacuum is a must.

In order to minimize any excessive release of spores into the air during the initial vacuuming process, no beater bars or other agitation at the vacuum head should be employed. Proper vacuuming procedures are also important. This means that overlapping strokes and a steady, but not fast, vacuum speed should be employed.

Using these well-respected vacuuming techniques actually provides three significant benefits. Minimizing spore dispersal so the mold from the carpet doesn’t spread to other areas keeps the potential problems where they belong. Several years ago, a carefully controlled study of remediation techniques showed that a careful pre-vacuuming of the moldy surfaces was the most important single factor in reducing airborne cross-contamination.

A second benefit of proper vacuuming is that it pulls the loose hyphal fragments up along with the spores. Even if the initial vacuuming doesn’t remove all of the mold filaments, breaking sections of those wrapped around carpet fibers facilitates the later “unwinding” of the hyphae during later cleaning steps.

The final benefit of effective vacuuming involves the loose soils which are extracted from the carpet. The greater the amount of organic material that can be removed, the better the chance that the chemical cleaners used in step two will be able to effectively clean, oxidize and detoxify the remaining mold fragments.

Chemical & physical removal

One of the reasons that cleaning moldy carpets is effective today (as compared to when the mold remediation industry exploded onto the scene as a subset of restoration work) is because the products and application techniques for addressing mold with chemicals has gotten so much better. It is no longer necessary to rely on harsh chemicals which can damage carpet fibers just to ensure that they are effective at loosening/dissolving mold.

Some of the more innovative carpet cleaning chemistries also provide a residual sanitizing effect which is essential in addressing the concerns of regrowth, if some spores are accidentally left behind.

The basic configuration of ‘hot water extraction carpet cleaning equipment’ looks similar to the units introduced in the 1960s; however, the physical similarities are deceiving. Modern carpet cleaning equipment, particularly truck-mounted units, are much more effective than their counterparts of 50 years ago.

Using powerful carpet cleaning equipment does not guarantee the removal of the mold unless it is matched with proper chemistry. From a procedural standpoint, using an EPA-approved, anti-microbial cleaning agent for mold on carpets not only makes sense but significantly reduces liability. Employing chemicals specifically designed as anti-fungal carpet cleaners makes the most sense.

The third step in the multi-phase approach is the proper drying after vacuuming and hot water extraction, and an appropriate mold-cleaning chemistry has been completed. This drying should involve the use of HEPA-filtered negative air machines in an air-scrubbing mode, along with floor fans and dehumidifiers. Eventually, this safety precaution against cross-contamination will likely be modified as additional data becomes available, confirming the effectiveness of the cleaning process.

Test results. Figure 1. (Photo: Wonder Makers Environmental)

Proving that it works

The remediation industry is not going to migrate from a ‘remove and replace’ approach to a ‘clean and save’ process for carpets unless there is solid evidence that the method is effective. In addition to laboratory studies in controlled conditions, amassing data from field projects will assist with the transition to effective cleaning. Figure 1 provides one sample of analytical data collected for a project. The collection of both air and surface sampling data confirms that the three-step cleaning process can be an effective alternative to replacing carpets contaminated by mold growth.

Michael A. Pinto, CSP, CMP, ( is the CEO of Wonder Makers Environmental and writes extensively about best practices in mold assessment and remediation.


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