Centralized heating and air conditioning systems rely on a series of ducts to carry cool air to the various corners of your home. They do the same job in the winter when it comes to hot air from your furnace. They do their jobs well in most cases, and because they’re usually hidden behind the walls or in the attic, they don’t often suffer damage. When they do, however – or even when age and wear-and-tear create leaks or breaches – then it can be very hard to spot the damage.