evidence: Various types of masks, goggles, and face shields are worn alone or in combination to provide barrier protection. A surgical mask protects a patient against microorganisms from the wearer and protects the health care worker from large-particle droplet spatter that may be created from a splash-generating procedure. When a mask becomes wet from exhaled moist air, the resistance to airflow through the mask increases. This causes more airflow to pass around edges of the mask. The mask should be changed between patients, and if at anytime the mask becomes wet, it should be changed as soon as possible. Gowns are worn to prevent contamination of clothing and to protect the skin of health care personnel from blood and body fluid exposures. Gowns specially treated to make them impermeable to liquids, leg coverings, boots, or shoe covers provide greater protection to the skin when splashes or large quantities of potentially infective material are present or anticipated. Gowns are also worn during the care of patients infected with epidemiologically important microorganisms to reduce the opportunity for transmission of pathogens from patients or items in their environment to other patients or environments.