is defined as the area immediately adjacent to the employee's nose and mouth; a hemisphere forward of the worker's shoulders with a radius of approximately 6 to 9 inches.

is described by a hemisphere of 300 mm radius extending in front of a worker's face and measured from the midpoint of an imaginary line joining the ears.

The worker's breathing zone is described by a hemisphere of 300 mm radius extending in front of their face and measured from the midpoint of an imaginary line joining the ears.

Envelope of air surrounding a person's head. This zone of air is presumed to have the same concentration of contaminant as the air being breathed by the person.

That zone of the surrounding environment in which a person performs the normal respiratory function.

A zone of air in the vicinity of an organism from which respired air is drawn. Personal monitors are often used to measure pollutants in the breathing zone.

Area of a room in which occupants breathe as they stand, sit, or lie down.