All ANAVI Gas Detector kits include a MQ-135 analog gas sensor module for detecting air quality. According to the data sheet of MQ-135, the sensitivity characteristics of the sensor depend on temperature and humidity. Because of this, the Advanced and Developer kits of ANAVI Gas Detector also include a HTU21D I2C temperature and humidity sensor module. For everyone's convenience, the default Arduino sketch for ANAVI Gas Detector supports both Celsius and Fahrenheit.