Full face (and possibly throat) protection from splash and/or impact is commonly required for work on or in the presence of human pathogens, some laboratory chemicals, explosion hazards, heavy grinding and heavy spraying or splashing, and with large (2 L and larger) quantities of dangerous liquids such as acids, bases, and many organic liquids. A face shield can also afford extra protection against extreme temperatures. If the faceshield is the type which has a wide opening on the sides or bottom, and when quantities of dangerous liquids are very large (4 L and over), protective eyewear must be worn along with the face shield. Your work area's hazard assessment will tell you if a face shield is required for specific work.
Protection of the face, eyes, and sometime throat by the use of a helmet or cap-like device fitted with a clear plastic shield to resist splashing and/or impact. Throat protection is especially necessary in the presence of chemical reaction set-ups which, because they are large and/or potentially violent and/or of unknown nature, could deflagrate or detonate and send glass and chemicals flying.
Inspect the face shield for scratches, flaws, fogginess etc., which would degrade visoin quality, and for weaknesses, cracks, or other imperfections (such as the attachment points of the visor to the headgear) which are out of perfect order. Replace defective equipment before proceeding. If the headpiece is adjustable, loosen the fitting and carefully snug it to your head so that it is comfortable and balanced, and so that the shield, when lowered, covers adequately (full-length face shields should cover to the clavicles (collarbones), and should completely protect the throat and neck from lacerations and punctures). Removal (doffing) or the face shield requires no special instructions unless there has been contamination by hazards such as radioactive, chemical, or biohazardous materials. If this is the case, depending on the extent of the contamination, it is usually best to remove the face shield while you are in the emergency shower, after the contamination has been removed (or while it is being removed).
Face shields will prevent or minimize injury from splashes and flying objects, but depending on the potential force of a violent event they might provide enough protection. Read the manufacturer's instructions for the shield, understand the potential for violence of which your work might be capable, and pay careful attention to your workplace hazard assessments and standard operating procedures. A blast shield is appropriate between any potentially violent reaction set-up or apparatus.
Manufacturer's instructions will stipulate any special considerations or limitations, but in general your face shield will last for years if kept clean and free of chemicals by using mild soap and water, and if stored in a protected, dry, and temperate storage location. On most makes and models of face shields, the replacement visors may be purchased. If protective items are not contaminated with chemical, biological, or radioactive material, there are no special disposal considerations; they are regular trash.