A multi-point air sampling system that can use a field reference subsystem to process sensor feedback to efficiently and reliably monitor and improve air quality within a space. The field reference subsystem can interface with multiple types of multi-point air sampling systems to ensure that sensors are operational and producing accurate measurements. Included within the field reference subsystem can be one or more permeation sources for generating test gases used to evaluate the integrity of the sensors, a processor for receiving the results of the test-gas evaluations to recurrently verify the operation level of each sensor, and a reporting system for carrying out actions in response to the recurrent verification of the sensors.