If you are fit tested with an M.S.A. half face small respirator, can you switch into 3M half face medium respirator without checking its fitness?

• A. Yes
• B. No
• C. Only if the new respirator is the same model
• D. Never

Answer: (D)

Fit testing ensures the respirator actually seals on your face during real use. Different brands and different sizes can sit and seal differently on your facial contours, so a seal that was achieved with a small M.S.A. half-face doesn’t guarantee a proper seal with a medium 3M half-face. Because the facepiece geometry, strap tension, and sealing surfaces vary, you must be re-tested for the exact respirator you plan to use. A user seal check is good for catching obvious leaks before use, but it doesn’t replace a formal fit test. So you should never switch to a different brand or size without a new fit test.