This happened three years ago but anyways. I was setting up some 6" fresnels in a multipurpose room in my high school. Conviently this room actually has 3 battens above the drop ceiling and a distro in the ceiling with camlock drop cables. The lights we were using had been stored in a maintence room for a few years as we hardly ever needed them. There were shows in two other spaces of the school so we decieded to pull them out of storage. We threw all the lights on the battens and hooked up the portable dimmer rack and board. We brought the fixtures up to full and immediatly one of the lights started smoking. This happens once in a blue moon in our school as the lights (especially older ones that aren't used often) get fairly dusty and the dust on the lamps burns off. But after a minute of so we could see a flame coming from around the lense. We flipped the breakers for the power feeds and went after it with a fire extinguisher but not before it scortched a few ceiling tiles. After getting the situation all sorted out we fould that the closet the lights were stored in had a furnace that ran on heating oil. Recently oil had started to leave from a pipe above the lights and literally coated the light in oil. Needless to say the electrical on the light was totalled and we never stored lights there again.