Final answer:
Air in a hydronic heating system reduces conduction, causes corrosion, and disrupts fluid flow, leading to noise, uneven heating, and inefficiency.
Step-by-step explanation:
Air within a hydronic heating system can be detrimental for several reasons. Firstly, air is an excellent insulator and this property can hamper the efficient transfer of heat throughout the system by reducing conduction. As in the example from the reference material, if the system relies on convective heat transfer, the presence of air disrupts this process because heated air tends to rise, and there's little convection downward, where it's often needed.
Secondly, air can cause corrosion inside the system which compromises the integrity of the components and leads to potential system failures. Thirdly, trapped air within the heating system can create noise and impede the flow of the water or heat transfer fluid, leading to uneven heating and inefficiency.