The vertical duct between grid lines 4 and 5 is connected to which air handler?

Understanding the connection of the vertical duct between grid lines 4 and 5 to the appropriate air handler requires examining the layout of the system as provided in the print. Typically, grid lines represent specific locations or measurements on the blueprint, while air handlers are identified by their designated labels or numbers in the drawing.

In this case, if the vertical duct between grid lines 4 and 5 does not connect to any of the air handlers labeled on the plan, it indicates that this duct might serve a separate purpose or a different system altogether. "None of the above" is the appropriate choice if there is no clear indication in the blueprints that ties the duct to any numbered air handler, suggesting it might be part of a ventilation or exhaust system instead.

This conclusion also reinforces the importance of examining all relevant details on the print to accurately trace ductwork and its connections. Each air handler usually has specific ducting that integrates the system's airflow. If the duct in question does not connect to any of those specified handlers, then the correct understanding is that it is indeed not associated with any of the options provided. Therefore, the answer is "None of the above," as it reflects an accurate reading of the print's information regarding the duct's connection.