I would normally defer to our colleague sgunsel on this as far as area classification for printing processes is concerned, but I would like to know the standard used to classify the location anyway. From part of your second response ("... solvent-laden inks ...") I suspect the primary reference standard is NFPA 33. It doesn't directly address your proposed solution. Fortunately, NFPA 497 the "general" area classification standard does:
One thing that must also be considered is that the gases/vapors could "extend beyond the barrier" where it doesn't completely cut off the "normal" classification envelope, typically with a new hazard radius from the cutoff point. The new radius is the differential between original radius and the cutoff point.
Section 18.104.22.168 In cases in which an unpierced barrier, such as a blank wall, completely prevents the spread of the combustible material, the area classification does not extend beyond the barrier.
Last edited by rbalex; 11-02-13 at 02:10 PM.
Robert B. Alexander, P.E.
"I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)