2 layers of drywall on ceiling

[Dan Johnson]

Recently purchased a 4 unit quadplex with 2 units downstairs and 2 units upstairs, and currently renovating one of my downstairs units. Upon ripping out the ceiling drywall we noticed that the ceiling had 2 layers of drywall. I'm guessing it has been like that for several years. Either the previous owner thought he was fireproofing/insulating between the 1st and 2nd floors, or was just too cheap to replace the drywall correctly (most likely).

I'm now wondering if I should rip out the ceiling in the other downstairs unit. My question is: is it safe to have 2 layers of ceiling drywall? Seems like unecessary extra weight. Has anyone ever heard of 2 layers of ceiling drywall falling down because it was too heavy?