I thought the formaldehyde was the cause of the stink?
I've done and keep doing reading on this and Union's old white sheets are chock full of info, I learned a good bit from them. Although they surely need an update by now, I especially like that they were contacting the EPA back then to confirm any regulations in place regarding the components.
What you are smelling out the dryer is the by products of the ZFS activator doing it's thing with the water base ink base. So yes, it's related to having the activator in there but you're not smelling the actual activator, just the stuff it breaks down into. I suppose if the dryer was poorly ventilated or had really low air flow or power,
(i.e., not suited for wb/dc inks) one might end up smelling some ZFS as it lingers around at low-mid temps waiting for cure to initiate for too long.
So when ZFS cures it puts off something like carbon monoxide, carbon dioxide, sulfur dioxide and zinc oxides if I'm getting that all right. All pretty obvious things to vent completely out of the shop, some irritants. Other, in particular, zinc oxides are a hazard and can give you heavy metal fever if you are over exposed which is probably occupational safety concern #1 with this ink system. I think it's pretty hard to get hit with metal fever but when you do it's a very bad deal. There are TLVs in place for this but I'm not sure how one goes about measuring for it. My approach has always been massive air exchange in addition to dryer ventilation.
My theory on the stank is it's gotta primarily be the sulfur dioxide right? No idea what zinc oxide might smell like. We've also notice that inks with an "off" ph reek like somebody was burning liquid poo when curing. Last off, I think some pigments can add to the smell factor.
I can't be sure but I would guess that you would not measure very much formaldehyde in a shop running DC and curing with a properly vented dyer. Especially if the ink mfg put a scavenger (which I'm pretty sure Union did) to eat up any remaining formaldehydes not converted to the other nasties during the curing process.
