“How can we use a fan to control gases?”
Most HVAC systems by moving around gases. However, materials at this phase can be quite difficult to control, so how can we use our engineering mindset to create such a mechanism? Well, we know that blades on a turbine react when a fluid passes through it, and through symmetry we can assume that a fluid will react to motor movement. So what if we were to construct something similar (like a motor) that would take in the gas, impart kinetic energy through its centripetal acceleration, and then change its direction by 90 degrees? Well, this is the fundamental idea behind a centrifugal fan and is one of the most fundamental components of modern HVAC systems.