About your problem, i use my 4 printers in the same room where i work for 8-10 hours/day every day. I print with a lot of material including nylon(glass and carbon too), petg(glass and carbon too) PLA, HT PLA, TPU TPE, wood stone and other compound of the PLA and also i smoke 4-5 cigarettes/day.
Up to today (so after 1 year and half) i have no troubles.3d printing chandigarth - fdm technology
But the biggest problem is when for some reason the filaments starts to degrade, in that case all filament start to produce toxic fumes due to charring of the filament material. like keeping the filament into the hot nozzle for a long time (ie. if you want to start printing but before do it you need to change something to the slicer setting or thing like that.)
And this is the only way for a REAL Pla to be toxic.
But if you start using low quality pla or a compound you have to know which kind of additives was used for the production and start thinking to a air extraction system.