N95 or N100 respirators are NOT to be used when there isn't enough oxygen, i.e. during a fire. They will however protect one from dust and non-oil aerosols.
There are respirators on the market that are rated for oil containing environments, those will filter out oil-containing aerosls.
I don't know about the charcoal impregnated kind, if they will actually filter out the smoke.
Look at Pandemicflu.gov, one doesn't really need N100 respirators to protect from the flu, N95 will do the trick.