hardwood-floorhardwood-refinishing
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, … ?
Get yourself a moisture meter ($30~) and test the floor at various points.
Wood is rarely COMPLETELY dry (as in no moisture at all) - but you definitely want a moisture content that compares to other wood in your house that was not flooded.
Unless you love spending time on your knees, rent the drum sander and the rotary edge sander. If you are worried about losing control of the drum sander, start with fine grit while you are getting the hang of it. Or ask the rental place to leave the old paper on it. It is likely to be toothless enough that it will be very hard to do any damage.
Orbital sanders are very slow, and generally are used for furniture making.
Sanding produces enormous quantities of dust. This is one reason you want to get done quickly. Even if you put plastic over the doors and heating vents, dust gets everywhere.
It's a good idea to have someone working with a vacuum as you sand. Get it off the floor ASAP so the next pass with the sander doesn't cast it into the air again. You will probably want to wear dust masks.
I have three sanders right now. A 7" disk sander that I can also put cuttoff wheels and wire brushes on, a 3x21 belt sander, and a 4x5 orbital sander. All 3 get used regularly, but for a floor project it would be the belt sander that would be used the ost.
Best Answer
NIOSH (National Institute Of Safety and Health) does not manufacture respirators or dust masks, they conduct research and make recommendations for prevention of worker injury/illness. If their name is on a respirator it means they approve of it's use for the manufacturer's stated purpose.
Generally. you should wear a particulate mask or respirator when sanding, mostly because of the chance for lead in old coatings. For old varnish the chance of significant lead exposure is slim and no volatile organics will be released.
However, you should wear a N99 dust mask or P100 particulate respirator anyway because breathing airborne dust when you don't have to is dumb. Ever blow your nose after working in a dusty field? Do you really want that stuff in your respiratory tract?