Combining Adafruit’s CCS811 gas sensor with a Circuit Playground Express and two NeoPixel Sticks we can quickly put together a mask that displays our breath attributes. This setup will monitor temperature, carbon dioxide and total volatile organic compounds. The sensor is easy to work with using it’s I2C interface and pre-calibrated ranges. A mask is an ideal wearable as it provides a place to house the electronics as well as an option for continuous monitoring as it is a hands free device that could be adapted for exercise or sleep. The gas sensors TVOC monitoring can be used as an indicator of ketosis as it will detect acetone levels on the breath which is a by-product of producing ketones. CO2 levels can also be a helpful indicator of how much glucose is being burned versus fats.