Maintaining the health and safety of workers in the United States and globally is accomplished in part by reducing hazardous exposures through the use of personal protective equipment. Personal protective technologies (PPT) include respirators worn by construction workers and miners; protective clothing, respirators, and gloves worn by firefighters and mine rescue workers; and respirators and protective clothing worn by healthcare workers. An estimated 5 million workers are required to wear respirators in 1.3 million U.S. workplaces. For some occupations, such as firefighting, the workers protective equipment is the only form of protection against life-threatening hazards; for other workers, the PPT is a supplement to ventilation and other environmental, engineering, or administrative hazard controls. In the United States, federal responsibility for civilian worker PPT is integral to the mission of the National Institute for Occupational Safety and Health (NIOSH). This book examines the NIOSH Personal Protective Technology Program (PPT Program) and specifically focuses on the relevance and impact of this program in reducing hazardous exposures and improving worker health and safety.