Defining and Detecting Toxic Black Mold in the Home

Corner of a room filled with black mold

Stachybotrys chartarum, or black mold, is a type of fungi that grows naturally in dark, damp areas. The ideal conditions for growth include high humidity (usually over 65 percent relative humidity) and an ambient interior temperature between 50 and 90 degrees Fahrenheit. This contaminant infests the home by releasing spores to the environment. These microscopic cells can become airborne very easily, and then attach to surfaces in wet, dark areas. When the spores settle on a surface and begin to germinate, they produce a branching network called hyphae.

Because black mold cannot survive without moisture and a dark environment, any ongoing issue in the home such as an unnoticed leaking roof or dripping pipe unseen under subflooring or behind interior walls only encourages growth. The mold then begins digesting the surface it is growing on in order to survive. Because it feeds on cellulose-based materials, it is a threat to the homeowner due to its infestation of wood, paneling, wallpaper, drywall, and other home building materials.

Because of its proclivity to grow in dark areas, black mold may go undetected for years before being discovered. A pipe under the kitchen sink can be dripping very slowly into the subflooring, and go undetected for a long time. Covered by paneling or kitchen cupboards, black mold has the opportunity to grow undetected. Slow buildup of moisture in a bathroom that is poorly ventilated can allow black mold to develop in wallpaper and areas unseen by the homeowner, such as under the bathtub. Bathrooms in older homes do not often have either windows or a ventilation fan. An airtight and unventilated attic, filled with insulation, can gather moisture due to the insulating properties of the construction, and give black mold an opportunity to get a foothold. The changing of the seasons in certain areas of the country enhance black mold's opportunity to grow. These results can be devastating to the homeowner in both terms of health hazards and undue expense in correcting the situation.

wiping black mold off of a wall

Although it is hard to believe, newer home construction is probably a better environment for toxic black mold to grow in than older homes. Due to bills passed in Congress demanding better energy efficiency in new home construction in recent years, newer homes are more airtight than older ones are, giving black mold a better breeding ground. Prior to this, excess production of mold spores was usually diluted by the regular exchange between indoor and outdoor air. The money saved in home efficiency is now outweighed by the risk of health hazard to the homeowner, and resulting doctor and hospital bills.

A regular inspection of the home is one of the easiest ways to detect the presence of toxic black mold. Although studies have shown that the presence of this particular health hazard is not as common as one might think, if you live in an area of the country that has high temperatures and humidity, has a changing of the seasons that produces a lot of moisture, or live in any area prone to flooding, it is a safe bet that the environment is right for the growth of black mold.

black mold above a window frame

Conduct regular inspections of areas that might be conducive to black mold growth, including bathrooms, kitchens, attics, and interior walls and ceilings. Often, the presence of black mold is not detected until major interior reconstruction, such as redoing a bathroom or kitchen. Interior water carrying pipes that "sweat" and are in a closely contained area are susceptible to black mold growth. A toilet that sweats in high humidity summers can also encourage growth. Knowing what to look for, and where to look, are important to the safety of homeowners. Regular inspections for leaking and moisture building conditions are a must in combating of toxic black mold.

Alden Smith is an award winning author and regular contributor to He writes on a variety of subjects, and excels in research.