Yes, there are actually 3 ways that a dirt air vent system can make you sick. First and foremost is the poor air quality that could be circulating in your home and when you have someone living in your home with asthma or other breathing conditions, dirty ducts can only make them worse. Dirty ducts have even made their own disease, Sick Building Syndrome. This happens when dirt, dust, and dander build up in your ducts and when inhaled, there have been some cases that have caused severe respiratory disease. The spreading of disease is also a major concern with dirty ductwork and tends to affect most people with asthma and infants, resulting in sore throats, coughing and a worsening of the condition.