Respiratory fit testing is an important part of Cal/OSHA respiratory protection requirements because it helps ensure that a respirator forms a proper seal against the employee’s face and provides the intended protection from airborne hazards. A properly fitted respirator can significantly reduce an employee’s exposure to dust, fumes, vapors, gases, smoke, and other potentially harmful airborne contaminants. Fit testing also helps identify whether a particular respirator model and size are appropriate for the individual employee and should be completed before an employee is required to use a tight-fitting respirator and periodically thereafter as required. Facial hair, changes in weight, dental changes, scarring, or other changes to facial structure can affect the seal and may require additional fit testing.