Mold Odors 101: Everything You Need to Know

mVOCs: Mold Odors, Health Risks, and How to Reduce Them Indoors

When you walk into a damp basement or a musty-smelling room, you’re not just smelling “old house odor.” Chances are, you’re inhaling mVOCs—microbial volatile organic compounds. These are gases released by mold and bacteria as they grow indoors. While many people are familiar with VOCs from paint, cleaning supplies, and building materials, fewer know about mVOCs. But understanding them is critical for anyone concerned about indoor air quality and health risks tied to mold exposure.

In this blog, we’ll break down what mVOCs are, how they affect your body, and practical steps you can take to reduce or remove them from your living spaces.

What Are mVOCs?

mVOCs, or microbial volatile organic compounds, are gaseous byproducts of mold and bacterial metabolism. Think of them as the “breath” of microbes. When mold is actively growing on surfaces like drywall, carpet, wood, or insulation, it doesn’t just stay put—it releases gases into the surrounding air.

Some of the most common mVOCs include:

• Alcohols
• Aldehydes
• Ketones
• Terpenes
• Sulfur-containing compounds

These gases often create the signature musty, earthy smell that people associate with mold. However, it’s important to note: odor strength doesn’t always equal risk level. Even low concentrations of mVOCs can cause irritation or discomfort, especially for sensitive individuals.

How Are mVOCs Different from Mycotoxins?

It’s easy to confuse mVOCs with mycotoxins, but they’re very different:

• mVOCs are gases—volatile, airborne, and responsible for mold odors.
• Mycotoxins are stable, chemical poisons produced by certain molds and found in dust or on surfaces.

Both can cause health problems, but mVOCs tend to affect you quickly through irritation and odor, while mycotoxins may have longer-term toxic effects.

Health Effects of mVOCs

Not everyone reacts to mVOCs in the same way. Genetics, immune health, previous exposure, and even gender can influence how your body responds. Some people may only notice mild irritation, while others develop stronger reactions.

Common health effects linked to mVOCs include:

• Eye, nose, and throat irritation – A burning or itchy sensation, similar to allergies.
• Headaches and dizziness – Particularly after spending time in musty environments.
• Nausea or fatigue – Some mVOCs have strong odors that can upset the stomach or leave you feeling drained.
• Respiratory symptoms – Wheezing, coughing, or worsening asthma.
• Difficulty concentrating – Brain fog or memory issues have been reported in cases of chronic exposure.

For sensitive groups—such as children, the elderly, or people with compromised immune systems—the effects can be more pronounced.

Why mVOCs Are Often Overlooked

One of the biggest issues with mVOCs is that they’re hard to measure and rarely tested. Standard indoor air quality testing typically looks for VOCs from chemical sources, not microbial ones. Because of this, a home or building may “pass” an air quality test while still harboring strong microbial contamination.

Additionally, not everyone smells mold odors the same way. Some individuals are hypersensitive, while others barely notice. This difference in perception often delays detection until visible mold growth appears.

Sources of mVOCs Indoors

You may encounter mVOCs in a variety of everyday places, such as:

• Basements with water intrusion or high humidity.
• Bathrooms with poor ventilation.
• Kitchens where leaks or damp cabinets go unnoticed.
• Attics and crawlspaces with moisture buildup.
• HVAC systems where mold grows on coils, ducts, or filters.

Any area with moisture + organic material + poor airflow creates an ideal breeding ground for microbial growth—and therefore, mVOC release.

How to Reduce or Remove mVOCs from Indoor Spaces

The good news: reducing mVOCs doesn’t require high-tech gadgets or complicated routines. It comes down to a mix of prevention, removal, and ventilation.

1. Control Moisture at the Source

Moisture is the fuel mold and bacteria need to thrive. Without it, mVOCs can’t be produced. Focus on:

• Fixing leaks in plumbing, roofing, or appliances.
• Using dehumidifiers to maintain indoor humidity below 50%.
• Improving drainage around your foundation to prevent seepage.

2. Increase Ventilation

Fresh air dilutes indoor pollutants.

• Open windows when weather allows.
• Use exhaust fans in bathrooms, kitchens, and laundry areas.
• Ensure your HVAC system has proper airflow and isn’t circulating damp, moldy air.

3. Clean and Remove Mold Growth

Physical removal is key. Sprays, foggers, or deodorizers may mask the smell, but they won’t eliminate mVOC production if mold colonies remain.

• Clean small areas (under 10 square feet) using non-toxic cleaners and scrubbing.
• For larger areas, professional remediation is recommended.

4. Upgrade Filtration

Air purifiers with activated carbon filters are particularly effective at capturing gases like mVOCs. Pairing them with HEPA filtration ensures both particles (mold spores, dust) and gases are reduced.

5. Use Safe Cleaning Agents

Harsh chemicals can add more VOCs to the air. Instead, consider enzyme-based cleaners or probiotic cleaners, which can break down organic residues without adding toxic fumes.

6. Monitor Indoor Air Quality

While direct mVOC testing is limited, keeping an eye on humidity, CO2 levels, and general VOC counts can serve as indirect markers of indoor air quality.

Long-Term Strategies for Healthier Indoor Air

Beyond short-term fixes, consider adopting habits that support healthier air year-round:

• Routine inspections of basements, crawlspaces, and attics.
• Seasonal HVAC maintenance, including duct cleaning if mold growth is suspected.
• Decluttering to reduce dust and organic buildup.
• Using low-VOC building materials when renovating, to reduce the chemical load and make microbial odors more noticeable if they develop.

Final Thoughts

mVOCs may be invisible, but their effects are real. That musty smell in your home isn’t just unpleasant—it’s a sign of microbial activity that could be affecting your health. By understanding what mVOCs are, recognizing their impact, and taking proactive steps to reduce them, you can protect both your indoor environment and your well-being.

Cleaner air means fewer irritants, more energy, and peace of mind that your home is truly a healthy place to live.