Occupational Safety and Health Administration. 1  Department of Labor, Labor Department, DoL, Labor - the federal department responsible for promoting the working conditions of wage earners in the United States; created in 1913.
The oxygen and carbon dioxide exchange take place in the alveoli. Primary bronchi are located on the upper portion of the lungs, secondary bronchi is located at the center of the lungs and tertiary bronchi is located near bottom of the organs above the bronchioles.
The bronchi (or bronchus) are the air passages into the lungs that begin at the end of the trachea. There are two bronchi, one for each lung. The bronchus divide into smaller branches known as segmental bronchi, which divide again into bronchioles, and then again into terminal bronchioles.