The best type of surgical/industrial mask to get is an N95 mask with an exhaust valve (a little plastic one-way valve in the middle of the mask). This permits humid exhaled air to exit without compromising the filter material.
Home Depots in my area still have plenty of ordinary N95 masks (sans valve). The exhaust valve type can be procured from an industrial supply/safety vendor.
Just don't get an ordinary dust mask; an N95 mask is required to provide the require particle filtration.
great, thanks. How long do they last?