How to Determine Types of Mold Growing in a House

Stachybotrys atra or "black mold" grows on wood building materials or walls.

Around 1,000 different types of mold can be found in houses. Molds are divided into three major categories: allergenic molds, which are not life-threatening and tend to only affect people with allergies or asthma; pathogenic molds, which cause infections in people with compromised immune systems; and toxic molds, which cause serious health problems, even death. The most common types of mold that grow inside houses are aspergillus, alternaria, cladosporium, Stachybotrys atra, mucor and penicillium. Because many molds look extremely similar, you can usually determine what types of mold are in your house by the location where the mold is growing.

Instructions

1. Identify alternaria mold in your house by looking for it in carpets, window frames, cloths and horizontal surfaces. You can also find alternaria outside your home growing on soil and plants.

2. Determine whether you have aspergillus growing in your house by looking for it on decomposing vegetables, stored food and soil. Penicillium also forms on decaying foods (this is the mold that grows on old bread) and soil, but it can also grow on dust, carpet, wallpaper and fiberglass duct insulation.

3. Look for cladosporium on fiberglass duct liners and inside supply ducts. Cladosporium also grows on dead and woody plants, food, soil, paint and cloth.

4. Identify Stachybotrys atra, more commonly known as "black mold," by its trademark dark coloring. Stachybotrys grows on wood building materials or other wet cellulose materials. You can usually find this mold growing under ceilings and behind walls.

5. Find mucor by looking for mold growing on animal feces, such as in your cat's litter box. Mucor is also found in dust and soil.

Tips & Warnings

• If you're uncertain about what type of mold is growing in your house, have the mold inspected by a professional mold-removal service or an environmental agency.

• If you believe you have Stachybotrys atra ("black mold") growing in your house, leave your house and contact a mold-removal company right away. Black mold is extremely harmful and can even lead to death in animals and infants by causing bleeding in the lungs.

• Don't attempt to clean pathogenic or toxic molds. Contact with or breathing in these molds is extremely harmful, and you'll likely need to contact a professional mold-removal service to evaluate the mold and remove it from your house.

References

• Advanced Mold Inspections: Mold Types and Mold Glossary
• Clean Water Partners: Types of Mold

Resources

• Centers for Disease Control and Prevention: Mold -- Basic Facts