Stationary CO2 wall meter with built-in EnOcean wireless transmission. CO 2 measuring up to 5000 ppm. For visualization there are 3 LEDs. Enocean is a manufacturer-independent standard for battery-free wireless sensor technology used primarily in the monitoring and control of home and building technology and differs from other wireless sensor systems used in building automation, such as ZigBee and Z-Wave, primarily by the principle of "energy harvesting", in which the sensors and switches operate predominantly without batteries.