Hint: A stolen raceway?
See answer below.
I must admit that I do not know if this box and electrical metallic tubing (EMT) was installed by an HVAC technician specifically for these pneumatic air lines, or if was stolen for this use. In either case, it’s a great opportunity for us to discuss Sec. 300.8, which strictly prohibits electrical conductors from being installed in any raceways that contain any piping, tubing, or its equivalent for air, water, steam, gas, drainage, or any other service other than electrical. Since the pneumatic air lines are already installed here, an electrician must not use this EMT for installation of any conductors. This would also include thermostat or other Class 1, Class 2, or Class 3 types of control or signaling circuits, since Sec. 725.3(K) requires Class 1, Class 2, and Class 3 circuits to follow the requirements found in Sec. 300.8.