Wearing a respirator can put an extra burden on the body. People with underlying medical conditions may put themselves at risk if they work while wearing one. So the Occupational Safety and Health Administration (OSHA) requires medical evaluation before any employee can even be fit-tested for — let alone wear — a respirator.
If respirators aren’t required in your workplace but employees wear them voluntarily, OSHA says you still he to perform a medical evaluation. The sole exception is if the only type of respirator voluntarily worn is a filtering facepiece respirator, though 3M still highly recommends evaluations in those circumstances.