In background quantities, molds can be found everywhere-in air, water, our homes, our clothing and even on our pets. They are present in such small numbers that they don't trigger reactions in humans, except in ultra-sensitive individuals.
But, when molds find the right combination of moisture, food and temperature, (and each species of mold needs a unique combination of food, moisture and temperature for optimum growth) they can propagate explosively. Removing any one of the three essentials will prevent their growth, and make adverse reactions in building occupants unlikely.
When evaluating the growth potential for mold inside a building, it is absolutely essential to measure the type and amount of mold in the air outside the building as well as inside. Normally, the amount and type of mold inside is about the same (or less) as found outdoors. If the indoor level is considerably higher than outdoors, it's likely there's a problem inside: a leaky roof, condensation on water pipes, or some other source of moisture inside the building. Of course, since molds can use wood and wallboard for food, and many of them like the same temperatures that you and I do, the one factor that controls mold growth indoors is the moisture supply.
So, if a building has a mold problem, or seems likely to, how can it be fixed? In some buildings, the source of moisture can be identified, isolated and controlled. But in others, the whole building promotes mold growth. Sometimes seasonal conditions (heavy rains, prolonged hot or cold periods, floods and the like) allow heat and moisture to get trapped, especially in 'energy efficient' structures, and the whole building becomes an incubator. Controlling water inflows is the single most effective means of preventing mold growth. In coastal areas and areas of prolonged high humidity, controlling the inflow of warm, moist air can be a problem.
Regular inspection of building areas known to be damp or wet, and immediate removal of the wetness through absorbent materials and de-humidifiers must be part of a good preventive maintenance program. Annual cleaning of air intakes, diffusers and filter boxes as well as the use of fungicidal paints, regular carpet cleaning and the immediate removal of moldy spots on walls, floorboards or other surfaces are equally important factors. I'll discuss this in more detail, in a later article.
Finally, the building management has to have authority to respond immediately to conditions that promote mold growth. The response must be fast and effective if Building-Related Disease or Sick Building Syndrome is to be avoided.