The surface-mounted sensor measures relative humidity and temperature of air and non-aggressive indoor gases. Moisture detection makes it possible to achieve a pleasant indoor climate and prevent mold. The accuracy of the humidity sensor is 2%. Optionally, the sensor is available with LCD and control elements. The device can be mounted directly on the wall, on a flush-mounted box or in conjunction with a surface-mounted frame available as an accessory. Predetermined breaking points for surface-mounted installations are available.