"Fluorescent light ballasts are among the most commonly overheated types of electrical equipment," says "Occupational Health and Safety." Some fluorescent bulbs have a ballast surrounded by a tar-like substance that is supposed to muffle the humming noise of an operating ballast. When a ballast fails, it causes increased heat, which burns the tarry substance and results in a foul odor. Older ballasts also can release PCBs (polychlorinated biphenyls), which were banned from fluorescent lights in the United States in 1978.
The ballast regulates the light intensity in a fluorescent bulb. A regular bulb produces light by heating a filament inside the bulb. Fluorescent bulbs produce light through gas that is excited by electricity. The ballast conducts the energy at either end of the tube and regulates the amount of energy. The gas, electricity and coatings inside the bulb combine to create a superbright source of light that would be too much for the bulb to handle without a ballast.
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Wet or Dry Ballasts
Wet ballasts contain a conductive oil or lubricant that enhances the transfer of electricity. Most of these would contain PCBs unless they were manufactured after 1978. Newer wet ballasts likely contain DEHP, or di(2-ethylhexyl) phthalate, which is clear and odorless but also could pose health risks after exposure. Dry ballasts became available in 1991 and use electronics to conduct energy instead of fluids. Newer types of fluorescent lights should still be recycled properly and handled with care.
As with any electrical situation where overheating is possible, a bad ballast can pose a fire danger. The overheated ballast could cause the plastic housing on the light itself to melt and, in the right conditions, flame up. Most bad ballasts simply burn themselves out, but it's still good to recognize the odor and find the problem. Overheated ballasts that release PCBs also may pose health risks because PCBs are possible carcinogens.
Disposal and Recycling
If you detect a foul odor that represents a bad ballast, turn off the light fixture and let it cool for half an hour. Wear rubber gloves and face and eye protection to minimize contamination. Make sure the power supply is off, and remove the lamp. Clean the housing by scraping any residue off and wiping with kerosene, turpentine or rubbing alcohol. Check with your city or county's hazardous waste department to find out the regulations for properly disposing of the ballast and contaminated materials. Ballasts that did not leak can be recycled by companies that handle fluorescent bulb reclamation.