Face shield windows protect workers from flying debris and chemical splashes. Full face shield windows cover the entire face to provide optimal protection in hazardous environments. Half face shield windows only protect the wearers' eyes, leaving the lower half of the face exposed. Both types of protective face shields are typically made of polycarbonate or cellulose acetate. Polycarbonate resists heat and impact and offers good visibility. Cellulose acetate resists more types of chemicals than polycarbonate.