As I put my ferments in the grow tent I asked my chemist degree owning dad about carbon dioxide production from fermentation. To work this out is surprisingly simple. Pretty much half the sugar you ferment via yeast turns to CO2 and the other half turns to alcohol. So put 30g of sugar in and get 15g CO2 produced.

How does that relate to ppm not sure at the moment but it's a start....perhaps someone else can help with that part.