from an attic

from an attic, a crawl space, or combustion air from a gas furnace, clothes dryer, stove, or water heater. If the supply duct system is leaking, the building can become depressurized, and air from outside may be drawn in to the ducting and distributed into the building. Either situation may decrease the quality of the indoor air. Research performed in the last 10 to 15 years has established these facts, and steadily increasing numbers of qualified HVAC contractors are learning how to eliminate duct leakage. How do you know if your duct system is in good condition? The most reliable and cost-effective way to find out is to have a duct test performed by a qualified contractor or technician using the proper test equipment. Duct testing is the process of using calibrated mechanical equipment to measure the amount of airflow that is lost through the duct system when it is at normal operating pressure. While some joints or seams may have only small leaks, other sections may be completely disconnected. Duct testing can indicate the relative leakiness of the ducts and help determine whether the duct system should be sealed, repaired, or renovated