This MicroSD card comes pre-formatted to FAT32 to work with applicable PurpleAir monitors (the Classic-SD, Flex, and Zen sensors). When you can’t connect to the real-time PurpleAir map, use this card for offline data collection. This card can store well over two years of data, although you should always check to ensure your data is being written correctly. Using SD data storage enables offline data collection. SD logs are not uploaded to the cloud by the PurpleAir sensor. If the sensor is connected to WiFi with an SD card present, data will be logged to the SD card and sent to the cloud.