Air Duct Sanitizing

Microbiological growth usually begins on the air handler evaporator coils

where there is moisture and darkness to support the growth of mold, mildew, algae, bacteria, viruses, and other contaminates

Further evidence of microbiological growth will appear

on the plenum above the air handler. If there is contamination bleeding on the outside, as pictured, you can safely bet that there is even more growth on the inside of the plenum

Contaminates will eventually show themselves

on the vents throughout the home if allowed to continue to grow and spread. Sensitization once a year will kill this growth and inhibit future growth.