Is it necessary to wear mono goggles under face shield while working with chemicals, if yes then why?

OSHA's eye and face protection standard,  CFR., requires the use of eye and face protection when workers are exposed to eye or face hazards such as flying objects, molten metal, liquid chemicals, acids or caustic liquids, chemical gases or vapors, or potentially injurious light radiation

Common eye injuries occurring at work can result from chemicals or foreign objects in the eye and cuts or scrapes on the cornea. Other causes of injuries include splashes with grease and oil, burns from steam, ultraviolet or infrared radiation exposure, and flying wood or metal chips

It is necessary to wear mono googles under face shield just because if we are using chemicals it is not good if it goes to our eyes it can cause blind ness. Aside this is the safety requirements.