The same CO2 sensors that call for make up air are hopefully monitored. Sick building syndrome.

Buildings are poorly sealed in my experience. In California code requires economizers on RTUs and they are almost always broken / stuck partially open. In the Inland Empire for example the actuators bind up from sand and often seize. Nobody wants to pay to fix just that, if they even know it’s busted.

I stay under 10 tons. Things are different in bigger buildings!