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Q: I like the fact that compact fluorescent light bulbs use so little electricity. But does the mercury in them make them dangerous when they burn out? Also, can you tell me why mercury is in there? Is it possible to make an energy-saving bulb without mercury or with less mercury? (Posted July 18, 2008)

 A: Good questions! The mercury in a compact fluorescent light bulb (CFL) stays safely sealed in an unbroken bulb whether the CFL is burned-out or not. The mercury is in there because it enables a CFL to produce light with little electricity. When electric current passes through mercury vapor, the mercury emits ultraviolet energy. When this ultraviolet energy passes through a bulb's phosphor coating, it produces light very efficiently; using as little as 25% of the energy that an incandescent bulb consumes.

            Some CFL manufacturers are leading an effort to reduce the amount of mercury in CFLs. Currently, most CFLs contain 5 milligrams of mercury, which is about a fifth of the amount in a watch battery. But newer CFLs, with as little as 1 or 2 milligrams, are starting to become available in some Vermont stores.

            Like any mercury-containing product, burned-out CFLs can't be disposed of in regular trash or recycling in Vermont. So, if you have unbroken, burned-out CFLs, you can take them to many Vermont hardware stores for free recycling. You also can take broken and unbroken CFLs to many waste-disposal facilities. To find a participating location near you, visit www.newbulbintown.com.

Rachael is a business development specialist at Efficiency Vermont. To find more energy saving tips or to submit a new question about energy use in your home or business, visit  www.efficiencyvermont.com/askrachael  or call, toll-free: 888-921-5990 to speak with a customer service representative.