Netatmo Weather Station : How does it works ? The Outdoor module measures the following parameters : - Temperature Humidity Microparticles It sends it with RF signals to the indoor module. The indoor module measures : - Temperature Humidity Microparticles Barometer CO2 Noise level The indoor modules then transmit over Wifi all those data (indoor and outdoor) to a Wifi router or access point. Those data are accessible from iPhone or other iOS devices.