A fly can be seen buzzing around Janeway's hair while consulting in sickbay. A Starship environment would not permit flies.
During the experiment where Kes shows Tuvok what she's learned about heating up tea, as the cup that she's staring at is about to explode, at the moment the cup goes up off of the table the remnants of the squib can be seen on the table including the fuse and the residue of the pyrotechnics used to lift the cup up. Which is what broke the cup in the first place.