They wore masks, had negative pressure ventilation suits on
I hope those were positive pressure suits, positive pressure helps to keep dust out of the suit. Negative pressure ventilation is used to help sick people breathe easier, like the iron lung for example.
Expat is short for expatriate, not ex-patriot. Both expatriate and patriot do come from the same Latin root (patria, fatherland) via French.
But yes, expatriate means someone who lives outside (ex) of their fatherland (patria) - can be used for both immigrant or emigrant, depending on context.