We all now know that fluorescent light bulbs are more efficient than standard incandescent bulbs and we have advocated replacing those with compact fluorescent lamps (CFL). In this column we will try to explain why they save energy, when they should and shouldn’t be used, and how to safely dispose of fluorescent light bulbs at the end of their lives.

A standard (incandescent) bulb works by conducting an electrical current through its fine tungsten wire, heating the molecules in it to almost white hot. Three percent of the electrical energy is converted to light, the rest is heat as can be experienced if you accidentally touch the lighted bulb. If the current is reduced, the light grows dimmer and more reddish. So if you wish to have a dimmable light, you should not replace that incandescent with a CFL. We use incandescent bulbs to heat our pump house during cold winter nights. Obviously replacing them with CFLs would not generate the heat we intended .

A fluorescent bulb works by conducting a small current through the mercury vapor that fill it. This excites the electrons in the mercury and it emits ultra-violet (UV) radiation. This, in turn, strikes the phosphor powder coating the glass. Depending on the phosphor used it will emit light (fluoresce) at various colors ranging from white to cool white, to blue, to blacklight (UV). The electrical energy needed to excite the mercury is about one third to one quarter that needed to heat tungsten for the same amount of brightness.

Some of the phosphors used are toxic in themselves and, of course, the mercury vapor is toxic, and can cause brain damage and other illnesses if inhaled or swallowed. Additionally, after many hours of use, much of the mercury is bound to the phosphor, making even an innocent phosphor toxic. This is why it is vitally important that ALL fluorescent bulbs, tube types, circular, or CFLs be recycled as hazardous waste. They should never be broken or mixed into household garbage headed for a landfill. The mercury-phosphor combination will leach into the ground waters if improperly disposed of. A hazardous waste landfill is built to prevent leaching of toxics into groundwaters.

Some experts warn that widespread use of CFLs will disperse more mercury into the environment. But others contend that the additional energy generated by coal fired power plants to power incandescent bulbs disperse more mercury into the environment than is contained in a CFL. The amount of mercury in a CFL is capped at 6 mg.

If a fluorescent bulb (of any type) is broken in the home, it presents a hazardous cleanup problem. Here is the latest recommendation from the Environmental Protection Agency (EPA):

Before Clean-up: Ventilate the Room 1. Have people and pets leave the room, and don't let anyone walk through the breakage area on their way out. 2. Open a window and leave the room for 15 minutes or more. 3. Shut off the central forced-air heating/air conditioning system, if you have one.

Clean-Up Steps for Hard Surfaces 4. Carefully scoop up glass fragments and powder using stiff paper or cardboard and place them in a glass jar with metal lid (such as a canning jar) or in a sealed plastic bag. 5. Use sticky tape, such as duct tape, to pick up any remaining small glass fragments and powder. 6. Wipe the area clean with damp paper towels or disposable wet wipes and place them in the glass jar or plastic bag. 7. Do not use a vacuum or broom to clean up the broken bulb on hard surfaces.

Clean-up Steps for Carpeting or Rug 4. Carefully pick up glass fragments and place them in a glass jar with metal lid (such as a canning jar) or in a sealed plastic bag. 5. Use sticky tape, such as duct tape, to pick up any remaining small glass fragments and powder. 6. If vacuuming is needed after all visible materials are removed, vacuum the area where the bulb was broken. 7. Remove the vacuum bag (or empty and wipe the canister), and put the bag or vacuum debris in a sealed plastic bag.