If you require dust masks as respiratory protection you must medically evaluate the employees first and perform annual fit tests.  (I assume by dust masks, you are using a niosh approved n95 or better.)

If this is voluntary use, you have to provide the employees with the voluntary use statement.

If you don't require the ppe, you should have employee monitoring showing that the respirable dust levels the employees are exposed to are below the PEL  (5 mg/cubic meter for 8 hour exposure).  Depending on what metals you are grinding, the permissible exposure levels may be lower.

What a coincidence!  I have a situation involving a contractor who is performing some welding for us.  He's wearing a dusk mask with a filter made into it.  I went online and found a similar mask which indicates that it's made to filter out dust and metal fumes.  I have to get the manufacturer information off the mask before determining if the mask he is wearing meets that requirement.  No respirator fit test is required if the job they are performing does not require a respirator.

Thank you for your help it was greatly appreciated.  I will have to exam further into our companies operations then to figure out if it is voluntary or required.

Thanks Again

OXBO Wisconsin