U.S. Department of Labor Occupational Safety and Health Administration

When are employers required to provide respiratory protection for workers?
You must provide and ensure the use of respirators when a PEL is exceeded.

In construction and shipyards, you must require workers to use respirators when performing certain work.

Generally, the level of exposure determines the type of respirator needed. In addition, the standards specify the type of respirator to be used for certain asbestos work. (See CFR 1910.134.)

Employees must get respirator training and medical clearance to use respirators.