Honeywell TH9421C1004 Visionpro IAQ Thermostat N/A Imported Advanced dual-fuel control. Three wires to the living space allows for easy equipment upgrade Thermostat requires the Equipment Interface Module or EnviraZONE panel MFG#THM5421C1008 (not included). Automatically raises humidity levels throughout all rooms in the home. Removes air pollutants by exchanging the stale air in a house with fresh air.