Mold Basics – Mold 101

What is mold?

Mold (or mould) is a microscopic fungi that grows in multi-cellular tubes or filaments called hyphae. The over 100,000 known species of mold play an important part in nature by breaking down or decomposing leaves, dead trees, and other organic matter and in the production of various foods, beverages, antibiotics and enzymes. Mold has attributes that resemble plants, but molds do not contain chlorophyll. They get nutrients by eating organic matter rather than through photosynthesis. They secrete digestive enzymes to dissolve food materials and absorb the soluble products from digestion.

Mold belongs to the kingdom fungi, separate from plants, animals, and bacteria. All molds are fungi, but not all fungi are mold. The kingdom of fungi also includes yeasts, mushrooms, mildew, rust, and smuts. The study of fungi is known as mycology, and is often considered a branch of botany, even though genetic studies have led to the consensus that fungi are more like animals than plants.

Why does mold grow in my home?

Different types of mold including black mold, toxic mold, and allergenic mold are present everywhere in the air we breathe. These molds need a nutrient source and moisture source to grow and reproduce. Indoors, the nutrient sources may include wood, paper, drywall, carpet, fabrics, or food, and the moisture source could come from a plumbing or roof leak, condensation, or even high humidity. Without a moisture source mold can remain alive in a dormant state for extended periods of time. Certain mold species are very tolerant to temperature, humidity, and pressure extremes, able to survive in harsh conditions like refrigeration, highly acidic solvents, petroleum products like jet fuel, and even the massive UV and cosmic radiation of outer space, proven lethal to other microorganisms. Mold spores exist in a dormant state, like plant seeds, until a source of moisture presents itself and growth and reproduction begin.

How do I know if I know if I have mold?

Mold is microscopic until it grows to cover a large enough area where it becomes visible. When conditions are right for growth, mold will expand and reproduce, appearing furry, woolly, cotton-like, or dusty. Any visible signs of suspected mold growth can be tested with a tape lift surface sample. This type of sample will determine what types of mold are present and their concentration in the small area of the sample. Air sampling is highly recommended to determine the types and levels of mold spores present in the air. Air sampling may lead to the discovery of hidden mold sources when multiple samples are taken and spore counts are elevated more in one area than others. Hidden mold sources are commonly found through analysis of multiple air sample results. Air sampling in several areas of a building will also show the affected areas of the building and the extent of airborne contamination, providing certified mold remediators necessary information that will be the basis for determining containment barrier locations.

The picture above shows hidden mold in a bathroom detected through air sampling. In the Mold Analysis Report below higher spore counts near the front entry helped to locate a hidden source of mold. Suspected areas of mold contamination prior to testing included the back wall of the condo due to poor grading, and the left bathroom and front entry ceilings where there had been a leaks from above. Additional wall cavity samples led directly to the source of the mold in a shower near the air handler.

How does mold grow?

Though mold grows on dead organic materials everywhere, it can only be seen through a microscope until it begins to grow into a network of branching hyphae known as a colony, fungal body or biomass, or more commonly, in technical terms, a mycelium. A single spore can blossom into a well developed colony in 24-48 hours. Typically, mold secretes hydrolytic enzymes which break down complex biopolymers like cellulose and then absorbs the simpler substances that result. Moisture and nutrients are transported throughout the mycelium, enabling the colony to grow and reproduce.

How does mold spread?

To reproduce, mold colonies can produce millions or even billions of spores so small that ten thousand would fit on the head of a pin. Spores from different types of mold vary in shape and range from 2 to 100 microns in size. Spores dispersion may be accomplished passively as spores are moved by a breeze or water drop, mechanically by a person or animal passing or disturbing them, or actively by the mold (usually under moist conditions or high humidity). A variety of spore discharge processes have evolved among fungi. Those with the longest ranges use hydrostatic pressure created by osmosis in the fluid filled stalks. These mold spore “squirt guns” are most common in Ascomycota and Zygomycota divisions which both include many species of mold. Recently, research using high speed cameras (250,000 fps) determined that some fungi discharge spores at up to 50 mph with the highest acceleration ever detected in nature, traveling one million times their width in one second. Spores can travel up to eight feet on their own or as far as the wind may carry them, which after long periods of mold growth, may include every part of the building it grows in. If the mold contaminated area is near an air conditioning return vent, spores can quickly spread throughout all areas supplied by that A/C unit.

How do I get rid of mold?

A small number of mold spores will almost always be present in the indoor air. They exist in large numbers in the outdoor air and can be carried into buildings through the air or on humans and animals. Mold spores will not grow without moisture, so controlling humidity inside the building can prevent growth. If mold is detected growing in a home or building, determining the moisture source is extremely important. Inspectors may use infrared thermal imaging cameras to detect moisture in walls and ceilings and trace the moisture migration back to a source. Any water intrusion problem should be corrected before remediation begins or the mold problem will likely return. Air sampling can be used to determine which areas of a building have been affected by airborne mold spores. The air in all affected areas should be treated to kill and remove spores. Porous materials like drywall and trim should be removed from the building. Contaminated structural framing members may be cleaned and sealed with an encapsulant. Removing large areas of mold can be extremely hazardous and should be left to certified remediators using proper protective equipment and removal techniques.