Terminix should be able to give you any information on the pesticides they use and any precautions to take. I would still cover the tank with plastic and turn off any pumps or filtration that could introduce air, at least until the room air clears out
I spray my own home for roaches and ants and what DED65 said. I cover the tank with plastic and turn off all pumps and I cover the topoff container just in case. I left the air settle for about 30 min or so then turn everything back on and have yet to have any issues. I cannot get the same stuff they use so not as strong but still same procedure.