Where can I get the Changers CO2 fit app? Changers Support December 15, 2016 09:48 Updated Follow The Changers CO2 fit app is available in a free version in the Google Play Store and the Apple App Store. Simply load onto the respective smartphone and get started. Related articles Which operating system version is supported? What does the Changers CO2 fit app cost? Comments 0 comments Article is closed for comments.