I understand that a NIOSH mask is necessary if one is applying an oil-based polyurethane.
Is a NIOSH mask needed or advised if one is sanding a hardwood floor with a polyurethane of unknown type, but one that has dried many years ago?
On the (very possible) case that the polyurethane used was an oil-based one, will organic fumes be released again when sanding a perfectly dried such hardwood floor?
Update
If an NIOSH-approved mask is recommended, Should I use an N95, N99, ... ?