Conservation of mass

All recipes should meet the physical laws such as the "Conservation of mass".
https://en.wikipedia.org/wiki/Conservation_of_mass

Units are not given in tons of even cubic meters. They vary based on what's practical and clear to read.
Is there a particular recipe which appears to be a problem?

Someone already wrote about it here and the answer was that it won't be like that. At that time, he wrote why more oxygen than hydrogen is produced from water, when the chemical formula is H2O. In the same way, there is a larger proportion of nitrogen (80%) than oxygen (20%) in the air.

Have you any idea about that's production technology and chemical? To seaprate air there are different methods with different results, so in game it just simplified.
For example with water, oxygen's atoms are in 16 times havier than hydrogen's. Then what state of them do we use in game: liquid or gas? They have different mass/volume characteristic.
And what mesurement units in game: mass or volume?
And what is preassure for gas balloons and pipes? For different products it could be different so the mass in one volume could be different...
And hydrolysis is very unefficient method so there might be difficulties to totally separate every all water moleculs.