1. An arrangement for use in an occupancy-based ventilation system, comprising: a plurality of CO2 sensors distributed throughout a plurality of spaces in a building, each of the plurality of CO2 sensors incorporated into a wireless sensor module, each of the plurality of CO2 sensors comprising a MEMS sensor, each space having a corresponding first damper configured to regulate a flow of fresh air into the space and a second damper configured to regulate a flow of other air into the space, the other air having a temperature that is different than the fresh air; at least a first processing circuit operably coupled to receive information representative of CO2 measurements generated by at least a first CO2 sensor corresponding to a first space, the first processing circuit operable to control the flow of fresh air into the first space via the first damper of the first space based on the CO2 measurements generated by the first CO2 sensor; at least a second processing circuit operably coupled to receive information representative of CO2 measurements generated by at least a second CO2 sensor corresponding to a second space, the second processing circuit operable to control the flow of fresh air into the second space via the first damper of the second space based on the CO2 measurements generated by the second CO2 sensor; first and second actuator modules, wherein first actuator module comprises the first processing circuit, and the second actuator module comprises the second processing circuit, the first actuator module further comprising a first wireless communication circuit communicating with a corresponding first wireless sensor module incorporating the first CO2 sensor, the second actuator module further comprising a second wireless communication circuit communicating with a corresponding second wireless sensor module incorporating the second CO2 sensor; wherein each of the first and second actuator modules further includes a wireless network interface; and wherein the first and second wireless sensor modules communicate with a control station for a building system via a corresponding one of the first and second actuator modules and a communication network, the control station including a user interface.