Which of the following is a common issue caused by poorly sealed duct joints?

Poorly sealed duct joints can lead to decreased air quality, which is a significant concern in HVAC systems. When duct joints are not properly sealed, conditioned air can escape into unconditioned spaces, such as attics or crawl spaces. This not only results in an inefficient heating or cooling system but also allows dust, mold, and other pollutants from these areas to enter the airstream. As a result, the air that circulates within the living spaces may contain higher concentrations of allergens, particulate matter, and other contaminants, leading to reduced indoor air quality and potentially causing health issues for occupants.

The other options do not align with the consequences of poorly sealed ducts. Increased energy efficiency, improved airflow, and reduced noise levels are outcomes typically associated with well-maintained and properly sealed duct systems, rather than those with leakage issues.