If the ducts are located near combustion-based appliances, there is the worry over carbon monoxide getting pulled into the air
The average American house loses up to 30% of heated & cooled air because of flaws in the HVAC duct. The duct system is a network of pipes that are largely concealed behind walls & ceilings & inside crawl spaces, garages, basements & attics. Due to bad design & wear & tear, separations can develop at the seams. Small holes can form. Conditioned air travels through the duct system various times per day. The air that is heated by the boiler or cooled by the air conditioner is distributed to the rooms of the house by way of the supply HVAC duct. The stale air is circulated back to the boiler & air conditioner through return ducts. Any imperfection results in air loss. Holes in supply ducts mean that the maximum amount of heated or cooled air fails to reach the intended endpoint. That means the boiler & air conditioner are required to run longer to meet the demands of the thermostat setting.The added wear & tear disadvantagely impacts the reliability & longevity of the equipment, leaky ducts lead to inferior comfort, greater energy consumption & higher running costs. Imperfections in the return ducts often draw in unconditioned air & pollutants. This can cause troubles with indoor air quality as well as health & safety risks. Contaminants get introduced into breathing air. If the ducts are located near combustion-based appliances, there is the worry over carbon monoxide getting pulled into the air. The solution is regular, professional HVAC duct testing, & if necessary, duct sealing. The process is non-invasive however worthwhile.