The use of respiratory protection systems in hazardous or toxic work place environments is discussed. Respiratory equipment selection is described based on the type and degree of exposure. Medical aspects of respiratory protection are considered, along with proper fitting techniques. Equipment maintenance and repair procedures are included. Four types of respiratory protective devices are described: air purifying, particulate removing filter respirators; air purifying, chemical cartridge and cannister respirators for gases and vapors; hose equipped, atmosphere supplying respirators; and self contained atmosphere supplying respirators.