[Dickie]

I would endorse everything Al has said - better be safe than sorry. The coating is likely to be an oil based varnish, and who knows what noxious fumes that can produce.
At work we have to produce equipment to meet some severe military specs. to do with salt spray and fungus growth. The pcbs get sprayed with a polyurethane varnish and if we have to work on them at all Health and Safety regs. say we must use a fume extraction system!