Mold Identification Guide

This guide provides images and descriptions of molds commonly found in the home. Results can start showing within 48 hours, but it's best to wait the full 4 days to get the most accurate result and to let the colors and growth patterns shown in this guide develop. Mold cultures often change in appearance as they mature.

Observation Tips
• Air samples tend to form distinct colonies in the dish.
• Swab samples form mold streaks in the dish.
• As the molds mature, they spread out in the dish, developing a variety of colors and growth patterns.

If the mold in your dish does not match the photos in the guide, don't worry. Sometimes there are several types of mold growing together in the dish, making visual identification difficult. The most important part of the test is finding out if you have mold present in your home.

Aspergillus

Grows in: Warm, humid areas (around 60–80°F).

Found on: AC systems, insulation, damp walls, and food.

Causes: High humidity, poor air flow, and dirty HVAC filters.

Health notes: Can trigger respiratory irritation or allergies, especially in people with asthma or sensitivities.

Cladosporium

Grows in: Moderate to warm temperatures (about 55–85°F).

Found on: Painted walls, fabrics, wood, and vents.

Causes: Water leaks, condensation, and poor ventilation.

Health notes: May cause skin irritation or mild allergic reactions; this is a very common outdoor mold that can enter homes.

Penicillium

Grows in: Cool, damp areas (around 40–70°F).

Found on: Wallpaper, carpet, food, and drywall.

Causes: Water damage, flooding, and slow drying after getting wet.

Health notes: Often linked to musty odors and can cause nasal congestion or allergic responses in sensitive people.

Alternaria

Grows in: Damp areas with moderate temperatures (around 60–80°F).

Found on: Bathrooms, windowsills, and kitchens.

Causes: Leaks, poor bathroom ventilation, and frequent condensation.

Health notes: A common allergenic mold that can be linked to sneezing, coughing, and mild respiratory irritation.

Stachybotrys (Often called “black mold”)

Grows in: Materials that stay wet for long periods (about 68–86°F).

Found on: Drywall, wallpaper, ceilings, and areas behind leaks.

Causes: Hidden leaks, flooding, and long-term high humidity.

Health notes: Long-term exposure may lead to throat irritation or coughing. It is mainly a concern when moisture problems are severe or ongoing.

Aureobasidium

Grows in: Warm, damp environments (around 70–90°F).

Found on: Caulking, bathroom walls, and window frames.

Causes: Condensation, leaking window or tub seals, and infrequent cleaning.

Health notes: May cause mild allergic reactions and is known for causing pink, brown, or black staining on surfaces.

Chaetomium

Grows in: Areas that stay persistently damp.

Found on: Drywall, insulation, and carpet padding.

Causes: Flooding, roof or pipe leaks, and trapped moisture inside building materials.

Health notes: Can cause mild allergy-type symptoms such as watery eyes or sneezing in some individuals.

Mixed Mold Growth

Many plates will show more than one type of mold at once. This is common, especially when plates are exposed to indoor air for several minutes.

Focus on the overall pattern: are there just a few spots of growth, or heavy coverage? Are the colonies mostly similar, or are there many different colors and textures?

Basic Mold Prevention Tips

  • Keep indoor humidity below about 50%.
  • Fix plumbing or roof leaks as soon as you notice them.
  • Use bathroom and kitchen exhaust fans when showering or cooking.
  • Dry wet materials within 24–48 hours.
  • Clean and maintain HVAC systems and change filters regularly.
  • Use dehumidifiers in basements or other damp areas.

Important disclaimer

Varify's Mold Test Kit and this guide are for at-home screening and education only.

  • This is not a laboratory test
  • This is not medical or health advice
  • We cannot provide exact species identification or assess your personal health risks

Visual identification is not exact — several molds look alike, and color alone does not tell you whether a mold is harmful. If you have health concerns, serious symptoms, or suspect a significant mold problem, please consult a qualified professional such as a licensed mold inspector, indoor air quality specialist, or healthcare provider.