I did some looking in my 3M catalog and honestly, you need REAL advice, call 3M at 1-800-234-4630.
As it says with every one of these "If exposure levels are not known use a fresh air system" And "each respirator must be properly selected based on the contaminant and concentration levels to which the worker is exposed."
The AMOUNT of exposure is very important too, what is the oxygen level in the room? This is very important. Call 3M and get the right information please.