Out with Mold

While mold itself is a common occurrence, it's essential to recognize that not all molds are created equal.

Traditionally, people have often referred to molds like Stachybotrys or Chaetomium as "black mold," even though molds can exhibit a range of colors, and not all of them are toxic.

Among the vast variety of molds, Stachybotrys and Chaetomium are known for being particularly toxic due to their production of mycotoxins. However, it's important to acknowledge that many molds can produce toxins, and molds that don't produce toxins can still have health effects on individuals, depending on their susceptibility.

In general, mold becomes problematic when it proliferates in excessive quantities or when it thrives alongside an active water leak (although mold can also grow with the presence of a small amount of moisture). Under such circumstances, any type of mold can have detrimental effects on indoor air quality, structural integrity, and potentially contribute to health issues. Therefore, addressing mold concerns promptly and effectively is crucial to maintaining a healthy living environment.

Ability to smell the mold: Unlike moisture or temperature meters, dogs can reportedly smell mold even when conditions for mold growth aren't ideal or when the conditions no longer exist, but the mold spores are still present.

Mold detection dogs detect mold itself by alerting to microbial volatile organic compounds (mVOCs) — gases released by dormant and actively growing mold. Canines can detect mVOC’s using the odor that travels to the closest opening, which could be a floorboard, electrical outlet, cracks, or other various openings.  

Mycotoxins - Canines might indirectly pick up on conditions that coincide with mycotoxin production. In our training , we focus on identifying mold colonies, which are the true source of both spores and mycotoxins.  

That’s the question we set out to answer—not just through experience, but through science. Mold is often an invisible threat. Its spores are microscopic and airborne, and the gases and toxins they produce can cause devastating health effects. So, can a dog—with its incredible olfactory system—actually detect mold in a structure?

Let’s begin with what we already know: dogs have been successfully trained to detect explosives, narcotics, electronics, and even disease. Some have tracked individuals with such specificity they could distinguish between identical twins. That level of scent detection operates at extraordinary sensitivity—down to the nanometer scale.

So yes, dogs can detect mold—but it’s important to understand what they’re actually alerting to. Is it mold spores? The mold colonies themselves? Or something even smaller?

Research and field experience suggest that well-trained mold detection dogs are often alerting to microbial volatile organic compounds (MVOCs)—gases released during active mold growth—or even mycotoxins, which are thousands of times smaller than mold spores. For scale: mold spores are about 2–100 micrometers wide, but mycotoxins measure just 1–5 nanometers. That means if a dog is detecting mycotoxins, we’re witnessing a biological feat of microscopic detection that machines can’t easily match.

But not just any dog can do this. It takes the right dog and the right training—rooted in proven science, repetition, and ongoing calibration with verified odor samples. These dogs are trained using the same scent detection standards applied in narcotics and explosives work, and they work alongside experienced handlers who understand airflow patterns, building dynamics, and the dog’s subtle alert behaviors.

When trained and deployed correctly, mold detection dogs can identify hidden mold sources—behind walls, under floors, or in other areas inaccessible to standard inspection tools—helping families uncover hidden threats to their health. This is particularly critical for those suffering from unexplained chronic symptoms, compromised immunity, or environmental sensitivities.

So, can a dog really detect mold?

Absolutely. And when guided by a skilled handler and backed by science, it becomes one of the most powerful, precise, and non-invasive tools available for identifying mold in a home or building.

In general, mold dogs are specifically trained to detect the unique odors associated with mold growth and spores (MVOCs) rather than the individual chemicals released by molds.

Mycotoxins—being so small—can pose a different challenge, since they don’t always present the same odor signature as the spores or active mold growth.

While it’s possible that dogs may indirectly detect conditions that coincide with mycotoxin production (like the presence of mold colonies), there isn’t a clear, standardized method for training dogs to single out mycotoxins alone.

Because some mold species can release mycotoxins when they’re dying or under stress, it’s understandable to be concerned about contamination in porous materials. In most practical situations, though, identifying where actual mold growth is taking place remains crucial, since that’s often the source of both spores and mycotoxins.

At MDK our approach in training our canines focuses on locating mold at its source, giving clients the best starting point for remediation and protecting overall indoor air quality.

Highly accurate and reliable K9 odor detection depends on more than a dog’s keen nose—it’s also the result of rigorous, ongoing training and the specialized skills of a dedicated handler. True professionals (think law enforcement, military), spend countless hours studying scent theory, refining canine behavior techniques, and honing their own observational abilities. They also spend a good amount of time continuing to train under senior level handlers/trainers– think of any athlete, or other TRUE professional for that matter.

They learn to recognize even the subtlest changes in a dog’s body language that signal a detection. This level of expertise can’t be achieved in a quick, one- or two-week class—it takes an extended period of committed study, hands-on practice, and mentorship from experienced trainers. The reliability of a properly skilled and seasoned K9 handler comes with years on the job.

A highly experienced K9 handler, on with scent detection expertise,  is as vital as the canine itself. Their judgment shapes the way searches are structured. Knowledge of airflow patterns and how to identify and interpret the dog’s signals, among other things, are a crucial part of K9 Scent Detection. It’s a delicate blend of art and science—requiring knowledge, trust, patience, and real-world scent detection experience such as narcotics, explosives, cadaver, etc.

When you have a skilled handler leading a well-trained detection dog, you gain an extraordinary tool that significantly reduces the margin of error, bringing peace of mind and reliable results to the task at hand.

This is why MDK ONLY works with highly trained, skilled and seasoned professionals with experience in K9 Scent detection for military, law enforcement and contract (such as FBI, DEA, etc.)

Our dogs are trained by professional K9 handlers with both law enforcement and military odor detection backgrounds that follow a very rigorous standard that is put to the test. The canine's intensive training involves hundreds of hours initially and continues daily with the handler continued scent calibration.

Our canine's training follows the same standards and methods used to train narcotics, explosive, ATF arson, and bomb dogs

Some molds are more than just allergens—they produce mycotoxins, toxic compounds that can severely impact health, especially for those with chronic illness, mold sensitivity, or certain genetic predispositions. The five molds most often linked to serious illness include: Stachybotrys, Aspergillus, Penicillium, Cladosporium, and Fusarium.

Stachybotrys (Black Mold)

Often called “black mold,” Stachybotrys chartarum produces trichothecenes, highly toxic mycotoxins that can affect the immune system, respiratory system, and brain. It grows on damp drywall, insulation, and ceiling tiles. Symptoms may include fatigue, brain fog, rashes, and in severe cases, neurological symptoms or respiratory distress. Professional removal is critical to avoid spreading spores.

Penicillium

Common in water-damaged homes, Penicillium appears on carpets, wallpaper, and insulation. Some species release ochratoxin A, contributing to asthma, fungal infections, and allergic responses.

Cladosporium

Often found on HVAC vents, painted walls, or fabrics, Cladosporium can aggravate asthma, emphysema, and chronic cough, especially in those with respiratory sensitivities.

Fusarium

Thriving in cooler areas like damp textiles or HVAC systems, Fusarium produces estrogenic mycotoxins that can disrupt hormones and affect the eyes, skin, and nervous system.

Aspergillus

Present in dust, drywall, and spoiled food, Aspergillus can trigger asthma or lead to aspergillosis, a serious lung infection in immunocompromised individuals.

Other Notables

Chaetomium: Found in water-damaged drywall; may cause skin and nail infections, or neurological effects. Alternaria: Common in showers and window frames; a major trigger for asthma and allergies

Stachybotrys is widely considered the most toxic, but any mold exposure can be harmful, especially over time. Individual response depends on immune function, genetics, and level of exposure.

Early detection is key. Mold Dog Knows uses trained K9 teams to identify mold quickly and non-invasively—so you can take the next steps toward recovery with clarity and confidence.