Mold is found everywhere and can grow on almost any substance when moisture is present. They reproduce by spores, which are carried by air currents. When spores land on a moist surface suitable for life, they begin to grow. Mold is normally found indoors at levels which do not affect most healthy individuals.
Because common building materials are capable of sustaining mold growth and mold spores are ubiquitous, mold growth in an indoor environment is typically related to water or moisture exposure and may be caused by incomplete drying of flooring materials (such as concrete). Flooding, leaky roofs, building-maintenance or indoor-plumbing problems can lead to interior mold growth. Water vapor commonly condenses on surfaces cooler than the moisture-laden air, enabling mold to flourish. This moisture vapor passes through walls and ceilings, typically condensing during the winter in climates with a long heating season. Floors over crawl spaces and basements, without vapor barriers or with dirt floors, are mold-prone. The “doormat test” detects moisture from concrete slabs without a sub-slab vapor barrier. Some materials, such as polished concrete, do not support mold growth.
Significant mold growth requires moisture and food sources and a substrate capable of sustaining growth. Common cellulose-based building materials, such as plywood, drywall, furring strips, finish carpentry, cabinetry, wood framing, composite wood flooring, carpets, and carpet padding provide food for mold. In carpet, organic load such as invisible dust and cellulose are food sources. After water damage to a building, mold grows in walls and then becomes dormant until subsequent high humidity; suitable conditions reactivate mold. Mycotoxin levels are higher in buildings which have had a water incident.
If unwanted water is not removed, mold can bloom within 24-48 hours. Mold grows and blooms wherever excess moisture is present. A variety of conditions can cause moisture problems, including roof, window and plumbing leaks, condensation, flooding, and excess humidity (generally above 60% – 70%). Tightly sealed buildings, such as those constructed during the energy crisis 20-30 years ago, may be a fertile environment for mold because they do not allow moisture to escape easily. There is also documented evidence indicating a high level of mold problems in newly constructed buildings, due to poor construction practices or using modern, water-permeable building materials such as gypsum board, plywood and paper-type insulation. Signs of a potential mold problem can include…
• Visible growth of mold or mildew
• Musty odors
• Discolorations on carpets, walls, floors, ceilings, and windowsills
• Building material deterioration
• Health complaints such as allergic reactions, respiratory problems, or other mold-related symptoms