Some people have used a water table to reduce the fumes, noise and distortion but this doesn't get rid of all of the fumes.
An extraction system will get rid of the fumes from your workshop but really needs to be connected to some sort of hood around the torch to work best. As for filtration then that's up to the owner but I wouldn't like to be one of their neighbours if there are running a plasma without filtration.
I do remember one company years ago was taken to task about the mess their plasma fumes did to a neighbours property. The shitty brown metallic dust was landing all over their garden/washing/car.