Mould spores thrive in temperatures 0 and 49 degrees Celsius (example: Air conditioning, evaporator coils). Germs are a class of contaminants includes bacteria, molds, mildrew, viruses and other microorganisms. Some germs can trigger allergic reactions, while others can lead to illnesses. Mold and mildrew can also stain walls, give rooms a musty odor and even cause structural damage to your home.