At a recent power plant fire in NYC the fire dept was given a report that the transformer on fire had less then 50 PPM of PCB's which is the environmental spill standard. The fire and smoke standard is any amount of 1 or more PPM (Parts Per Million) of PCB. This was a haz-mat fire and should have been fought with leval A haz-mat approach (reflective-NFPA) suits. Please pass this vital information along to any FD that would respond to a burning or smoking transformer. The transformer finns had extremely high levels (in the tens of thousands PPM)of PCB's and that mixed with the lower PPM cooling oil in the main transformer chamber during the fire. This caused the two oils to mix. You could also fight the fire outside the hot zone and the plume with structural firefighting suits and SCBA (mandatory). Don't forget the drivers. A safe approach is to treat all smoking/burning transformers as PCB transformers and use haz-mat or fight from warm/cold haz-mat zone.