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Respirators must be worn whenever it is necessary to protect the health of the employee from contaminated or oxygen deficient air, including situations where respirators are necessary to protect employees in an emergency.
However, employers must first use engineering and work practice controls, where feasible, to abate respiratory hazards. Only if such controls are not feasible, or while they are being implemented, may an employer rely on a respirator to protect employees.
A combination of administrative controls and respirators may be used as interim controls while engineering control measures are developed and implemented. However, some of OSHA’s substance specific standards (e.g., the asbestos standard) prohibit the use of employee rotation as an administrative control.