A face shield should:

To be effective, a face shield must be free of scratches; be resistant to penetration; allow clear views to both sides; fasten securely; permit air to pass through; and permit enough room for eyeglasses or sunglasses, if needed.

• Allow a clear view to both sides.
• Prevent air from passing through it.
• Be tight enough to prevent glasses from fitting underneath it.
• Should not fasten too tightly.