Aspergillus is one of the most widespread molds found indoors.

Unlike molds that require chronic water damage, Aspergillus can grow under relatively mild conditions, which is why it frequently appears in homes that look dry and well maintained.

Understanding how this mold behaves helps explain why it can be persistent and why cleanup efforts sometimes don’t hold.

What Aspergillus looks like

Aspergillus typically appears as a powdery or dusty growth.

Its color varies widely depending on the species and conditions, including green, gray, yellow, white, or brown.

Because it often blends into dust, it may not stand out as “mold” unless growth is heavy or widespread.

What Aspergillus needs to grow

Aspergillus is highly adaptable and does not require saturated materials.

Common growth conditions include:

• Moderate humidity
• Poor ventilation
• Dust accumulation
• Condensation in HVAC systems or ductwork

It can grow on drywall, insulation, fabrics, stored items, and inside air-handling systems.

Common exposure effects

Reactions to Aspergillus vary widely.

Some people experience no noticeable effects, while others develop symptoms with prolonged or repeated exposure.

Commonly reported effects include:

• Nasal congestion or sinus irritation
• Sneezing or allergy-like symptoms
• Eye irritation
• Respiratory discomfort or asthma flares
• Fatigue or difficulty concentrating

Symptoms are often more noticeable in spaces with poor airflow or heavy dust buildup.

Why Aspergillus is often missed

This mold does not always signal itself with obvious water damage or strong odors.

Because it can live in dust and ventilation systems, the source may be diffuse rather than localized.

Repeated cleaning without addressing airflow, humidity, or dust reservoirs can allow it to return.

Cleaning versus remediation considerations

For small, non-porous surface growth, careful damp cleaning and HEPA vacuuming may be sufficient.

However, when Aspergillus colonizes porous materials or HVAC components, surface cleaning alone is often ineffective.

Disturbing dust without containment can temporarily increase airborne particles.

Safe containment and remediation principles

Effective control focuses on reducing the conditions that allow growth.

Best-practice principles include:

• Lowering indoor humidity levels
• Improving ventilation and airflow
• Reducing dust reservoirs with HEPA filtration
• Removing heavily contaminated porous materials
• Cleaning HVAC systems when implicated

Containment is especially important when working in enclosed or poorly ventilated areas.

When professional remediation may be appropriate

Professional assessment is often helpful when:

• Growth involves HVAC systems or ductwork
• Large areas of porous material are affected
• Symptoms persist despite repeated cleaning
• Moisture or ventilation issues cannot be easily corrected

Addressing airflow and humidity is critical to preventing recurrence.