Simple app to convert the concentration of gas from ppm to mg / m3 and vice versa; it is sufficient to insert a mass and the concentration to be converted to obtain the result.
The app also has a database to store commonly used gases. The database entries are freely editable and eliminated by the user.
You can import a CSV database.
You can share the result with any third party app
Not much to say, it really is an app easy to use.