Hi @sisi
If you’re referring to the gas data found on SD cards, that is the experimental VOC data output by a sensor’s BME688 from Bosch. For more information on VOC data from PurpleAir sensors, look here: What Do PurpleAir Sensors Measure and How Do They Work?
Secondly, PurpleAir sensors do not measure Ozone. We did some initial testing with Ozone sensors in 2018, which is why there is an Ozone layer on the map, but concluded that it was not realistic to offer an Ozone option. Information regarding that testing can be found here: The Ozone Data Layer on the PurpleAir Map