That will depend upon the type of tank. If it’s the type that is used to provide propane for heating the facility, the requirements for locating and shielding should preclude it from being a hazard as such. However, if it is the smaller type that is used to store propane for such uses as fueling forklifts, such an evacuation route would not be acceptable.
According to 29 CFR 1910.37(a)(2), exit routes must not lead employees toward high hazard area unless the path of travel is shielded from the hazard. The definitions in 1910.34 have a high-hazard area inside a workplace; however, at 1910.36(e)(2) they indicate that it is an area with contents that are likely to burn quickly.
OSHA also indicates that danger to employees must be minimized. If sending them past a propane tank would put them at risk, it should be avoided.