Fodmap intolerance is linked to Irritable Bowel Syndrome (IBS). Food Chemical Intolerance is also linked to Irritable Bowel Syndrome (1BS). The difference is people with food chemical intolerance tend to experience many other symptoms as well See here.
If you mainly experience gut symptoms, not linked to Allergy , Celiac Disease, IBD or Food Chemical Intolerance, there is a good chance your symptoms will reduce by following a low fodmap diet for a period of time.
The best place to find out about fodmaps is at the Monash University Fodmap Diet Website Monashfodmap.com.
Can a low fodmap diet and a food chemical intolerance be combined ?
It depends on your level of intolerance to food chemicals, in particular salicylates. If you can tolerate higher levels of salicylates, it is possible to also eat a lower fodmap diet as well. However, if you are quite sensitive to salicylates, it is better to simply avoid dairy and wheat or gluten rather than try to combine both the fodmap diet and food chemical diet.