Which statement about air handling units is correct?

The correct answer is that air handler unit 3 measures 18'-6" x 29'-6". This specific detail provides essential information about the physical dimensions of the air handling unit, which can be critical for applications in mechanical systems where space considerations are important. Knowing the exact size is necessary for proper selection, installation, and integration within the overall HVAC system.

While other statements could address various functionalities or configurations of air handling units, they don't provide the precise measurement detail that option C offers. Therefore, understanding the dimensions of air handling units contributes significantly to effective planning and implementation in HVAC design and efficiently managing airflow in the system.