MSDS sheet should detail all hazards as to chemical exposure and toxic effects. Sounds like you need better ventilation. OSHA has rules as to number of air exchanges per hour, according to what processes. I worked in a City shop where due to poor ventilation, OSHA would only allow Fluorescent trouble lights due to their belief of explosion hazard.
Organic vapor mask (not the paper masks) like an auto paint shop uses should do, again check the msds, it should detail. BTW get the MSDS from your plastic supplier, give your employee a copy too.