Most are. We have not tested every oil yet. These are listed in our IFRA Compliance Sheets under category 11 (10A for the updated IFRA that will be coming ASAP for the new guidelines -  needed to switch to these new guidelines by May 2022) for maximum amount. Keep in mind this % is the absolute maximum but is not recommended for a usage rate. The ones we have tested have done pretty good around 25% FO (if the % allows). Scents that have cinnamons, vanillas, and overall are "thicker" consistency and may be more difficult to work with for diffusers. We strongly recommend that you perform your own testing and research for your personal preferences/safety for your business.