A safe and healthful workplace—a requirement for all workers—includes the air that workers breathe. Employers should approach control of hazards that threaten air quality with a hierarchy of control measures:

1. First and best is to eliminate the hazard

2. If that's not practical, a lesser hazard (different work process, less hazardous chemical) can be substituted

3. Engineering controls like adequate ventilation or changing the work process would be the next level

4. Administrative controls such as implementing safer work practices, instruction and training can be considered next

5. The last resort is the use of personal protective equipment

Respirators are one type of personal protective equipment, to be used only when engineering controls are not feasible. Before the worker is fit tested for a respirator, a medical evaluation is required to determine the worker's ability to use one, and a physician or other licensed health care professional must provide a written recommendation to that effect. The medical evaluation may need to be repeated if a change occurs that can affect the individual's ability to use the assigned respirator: weight loss or gain, facial hair, injury that changes face shape, or other medical conditions (OSHA 29 CFR 1910.134)

NIOSH (Medical Evaluation FAQs)

Fit testing (required)

• prior to respirator use
• confirms the fit of the respirator to the face with a tight seal
• repeated annually, and as needed in between
• repeated each time a new model, manufacture type/brand, or size is worn
• repeated if user's weight fluctuates or facial/dental alternations occur

NIOSH: What is a Respirator Fit Test