The answer to 'why is my dryer vent mildew' is that a clogged or blocked dryer vent is the most common cause of mildew buildup. Over time, lint and debris can accumulate in the vent, trapping moisture and creating an ideal environment for mold and mildew growth.
Symptoms of a mildew-clogged dryer vent include longer drying times, a musty smell coming from the dryer, and visible mildew growth around the vent opening. This can be a fire hazard and should be addressed promptly. The solution is to clean out the dryer vent, either through DIY methods or by calling a professional vent cleaning service.