How long can a tank survive covered?

My roommate's cat has fleas and we have to get the house completely treated/sprayed sometime this week. The exterminator said to unplug the filter and cover the tank up while they spray. They also said this will take about 4 hours.
I have about 9 shrimp in the tank-- can they survive this? Should I just a friend to take care of them for a few days?
Sorry if this is a dumb question, I'm relatively new to shrimp.