I am working on a device to detect different elements in the environment. Right now I am detecting methane, carbon dioxide, and volatile organic compounds, but I also need a way to detect volatile fatty acids (VFAs). From what I have seen, VFAs produce carbon dioxide and methane, are there any other other "signs" that could be used to find these in the air? For instance maybe a certain concentration of alcohol or hydrogen, or maybe a certain change in humidity or temperature.

Looking for methane and carbon dioxide looks like my best option, but I am not very informed about these fatty acids and I am not finding much online, so any help is greatly appreciated!

Some ideas can find here

https://en.m.wikipedia.org/wiki/Volatile_fatty_acids_analysis