Micro organisms grow on the COOLING COIL and POLLEN FILTER BOX. The most common micro organisms include: Cladosporium, Penecillium, Aspergillus and Alternaria. Some consequnces could be Whooping cough, Tuberculosis, Diphtheria, Meningitis, Pneumonia as well as Asthma attacks and allergic reactions. This not only impacts the health, but also the safety of the driver / passenger and others.