What's causing my duct work to pop when the furnace starts or stops?

A popping disturbance is a typically sign of an under-sized duct design. It may be attributed to greater air flow than the duct work is built for. Have a qualified company analyze your home's ventilation system for proper design and make necessary recommendations. Improper duct work layout can cause several ventilation and air quality problems, including: 

1. excessive noise
2. higher energy consumption
3. lowered life of the system
4. uneven temperatures throughout your home
5. damaged compressor in hotter months
6. overheated unit in the cooler months

In addition, if your ductwork is the wrong size you may have other issues, such as leaky ducts and poor layout that impacts airflow. In humid states this can encourage mold growth within your ductwork.