What is the primary purpose of a "P" trap in HVAC systems?

The primary purpose of a "P" trap in HVAC systems is to prevent condensation from entering the duct system. The "P" trap functions by creating a U-shaped bend in the drainage line, which holds a small amount of water. This water acts as a barrier, effectively blocking any gases or odors from escaping from the drainage system into the HVAC ductwork. By maintaining this seal, the "P" trap helps to ensure that only the necessary airflow passes through the ducts while preventing moisture that could lead to mold growth, contamination, or undesirable smells from infiltrating the indoor environment. This is crucial in maintaining indoor air quality and the overall efficiency of the HVAC system.