Who to call with a large mercury spillage?

It will depend where you live, but some state environmental or health agencies and the US EPA can respond and help or advise you on the proper cleanup procedures. If in a home, you should call immediately and ventilate the room. Avoid walking in or near the spill area. It does not take much to make a toxic hazard. Unless you know what you are doing, do not try to clean it up. You will likely just spread it around and make the situation worse. Mercury is toxic and volatile; it is an inhalation hazard and absorbs through the skin. It has no odor. Expensive sensitive instruments are required to detect it. Special equipment is generally required to clean it up. It is often necessary to remove and dispose of clothes, furniture, carpet, and sometimes floor boards.