When studying different HVAC systems, the diagrams are usually in section and show systems/components are on top of one another which makes it hard to figure out roughly how large these systems are or how far apart certain components need to be from one another. How far apart does your fresh air intake and exhaust air need to be? Could they be located on the same exterior wall or for example, does fresh air intake need to be on the north facade and exhaust air need to be on the east? Assuming that the mechanical room was on the corner of the building. Another scenario would be a restaurant kitchen not wanting it’s smelly exhaust air right next to the fresh intake air grille
As you elude to the answer to this question is situation dependent. The diagrams that you are talking about are one-line diagrams which are used by mechanical, plumbing, and electrical engineers to illustrate the basic concepts of the systems that they are designing for the building and identifying the major components and zones for the project. They get more detailed in plan and section drawings (which use architectural backgrounds) which is where you will find true distances between intake and exhaust ducts. The location of intake and exhaust relative to one another depends on the building type, the HVAC system, the site etc. For example, if you have a diesel powered generator on site near your mechanical room that is on a corner you will want the intake on the side of the building away from the generator. The exhaust is fine being right next to the generator. One general rule of thumb is that your exhaust will typically be warm air that will naturally rise so your exhaust wants to be above your intake. Your biggest concern will always be your intake. Look out for garbage bins, docks where diesel engines might be idling, and any other site element that might introduce contaminants.