Is it true that the air conditioning evaporative coil is perhaps the largest source of indoor airborne mold?
In most cases, yes. The dark, damp condition at the e-coil is ideal for the growth of many types of molds. The e-coil may be the single largest source for producing molds in an average home. In addition, mold growth at the e-coil and in the waste pan produces mycelium enzymes. These enzyme byproducts tend to be very sticky. It is often referred to as green (or black) slime in drip pans. The slime from the mold growth accumulating on the e-coil fins accelerates the collection of house dust and other organic materials on the metal fins. This organic dust and slime become nutrients for the growing molds and bacteria. This sticky enzyme material flows across the surface of the e-coil and between the fins, building to a point where airflow is limited. The enzyme stems produced here, caught in the passing air, go airborne, becoming some of the worlds most aggressive allergens. The World Health Organization (WHO) estimates between 60 80 percent of the primary causes for allergies and asthmas
