TVOC, Temperature and Humidity Sensor: An Aqara Hub is required and sold separately. Requires a secured 2.4 gigahertz Wi-Fi network connection. The Aqara TVOC Air Quality Monitor detects the concentration of the Volatile Organic Compounds (VOCs) which are harmful, carcinogenic air pollutants that evaporate at normal indoor atmospheric conditions, and measures temperature and humidity, which can also be used in smart home automations..3 CONTROL SETTINGS: Set single press, double press, and long press to control programmable functions, such as turning on/off a device, activating a scene, etc.E Ink Screen: The Aqara TVOC Air Quality Monitor equipped with a high-contrast dot-matrix E Ink screen which is similar to paper and protects your eyes consuming very little energy when showing the information..All-Round Compatibility: Zigbee 3.0 Protocol built upon the fastest and energy-efficient smart home technology with the focus on compatibility and stability. Apart from Aqara Home, it supports the most popular smart home ecosystems such as HomeKit, Google Home, Alexa, IFTTT and more..DOORBELL BUTTON: The device can also be used as a doorbell when connected to the Aqara Hub, which offers a selection of different ring tones. In addition, Aqara offers 12-months after-sales service. If you have any questions, please feel free to contact us.