Vitally important when cutting tesserae and mixing powdered adhesives and grouts.  Portwest valved disposable face masks with FFP3 protection.  Sold in packs of five.  These masks comply with SEN149:2001 which means that their design has been tested to the required UK standard.  Respirators are further marked with an FFP number; the higher the number the better the protection they offer if worn correctly.  These masks are FFP3 rated, the highest rating, and reduce the amount of dust and particles you breath in by a factor of 20.    

Check the fit of your respirator each time you wear it.   Ensure that the elastic straps and the moulded strip over the nose are correctly adjusted.  Test the fit by breathing in and out and trying to detect any leakage around your face.