Not sure what you mean by a basic dust mask but the N95 rated masks are good for considerably more than a few minutes in my experience. These generally have an exhale valve in the middle of the mask. The simpler and cheapest dust mask, the so called 'nuisance dust mask" is a little too basic. It really doesn't exclude all that much, even when fresh, although it is better than nothing at all..

None of these are very effective for vapors or gases. If I were working near a chemical plant with the possibility of hazardous emissions, I would want to get a mask and canisters rated for the probable chemicals I might encounter, if that is at all possible. What do you chemists say about this?