The study reported that even the tested devices which were enclosed still emitted plenty of VOCs:

"Interestingly, the presence of an enclosure only moderately reduced UFP emission rates from the MakerBot–ABS combination, with a ∼35% reduction in the median emission rate (although this variation is within the estimate of uncertainty). Larger reductions were not observed, perhaps because the enclosure was not completely sealed and large gaps were visible. While these two comparisons provide preliminary data on how printed shape and presence of an enclosure may impact particle emissions from 3D printers, no other definitive conclusions can be drawn given this limited data set."