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Compact Fluorescent Lights (CFLs)

Image of Compact Flourescent LightbulbCompact Fluorescent Lights (CFLs) are light bulbs that generate light when an electric current is driven through a tube containing argon and a small amount of mercury vapour. This generates invisible ultraviolet light that excites a fluorescent coating called phosphor on the inside of the tube, which then emits visible light.

CFLs are 75% more energy efficient than traditional incandescent light bulbs, but because they contain a small amount of mercury, they require more care when handling.

How much mercury is in a CFL?

A CFL contains enough mercury to produce the light, roughly the equivalent of the tip of all ballpoint pen or about one-fifth of the mercury found in a wristwatch battery. The chart below compares the mercury content in a CFL to other household items.

Comparison of Mercury Content in a CFL to Other Household Items
ProductAmount of MercuryNumber of Equivalent CFLs

Compact fluorescent lamp

5 milligrams


Watch battery

25 milligrams


Home thermometer

500 milligrams - 2 grams

100 - 400

Float switches in sump pumps

2 grams


Older manual home thermostat

3 grams


Guelph Hydro recommends that customers follow the manufacturer's instructions when using CFLs. To lower the risk that a light bulb will break when you are installing or removing the unit, hold the bulb by its plastic base.

How to Dispose of CFL Bulbs Safely

Because CFLs contain mercury, they require special handling and must not be disposed of with your regular household waste. For more information on the proper disposal of a CFL, visit the City of Guelph's Household Hazardous Waste site.

What to do if a CFL Breaks or Cracks

Health Canada provides the following procedures for handling a CFL that has cracked or is broken:

  • Remove people and pets from the room and keep them out of the room during the clean-up process.
  • Avoid stepping on any broken glass.
  • Open all windows to get rid of any vapours. Ventilate the room for at least 15 minutes prior to starting clean-up by opening windows and doors to the outdoors. This will ensure that mercury vapour levels are reduced before you start cleaning.
  • Wear disposable gloves to avoid direct contact with mercury and to prevent cuts.
  • DO NOT USE A BROOM OR VACUUM to clean up the initial breakage as it will spread the mercury vapour and dust throughout the area and may contaminate the vacuum. Scoop or sweep up the broken pieces and debris with two pieces of stiff paper or cardboard. 
  • Carefully clean broken pieces by wiping the entire area with a paper towel.
  • Use sticky tape, such as duct tape or masking tape, to pick up any remaining fine glass or powder.
  • Wipe the area with a damp paper towel, cloth or disposable wet wipe to remove any residual particles.
  • Place the broken glass and clean-up materials in a glass container with a tight fitting lid to further minimize the release of mercury vapour.

Carpeting - Steps to Take After the Initial Clean-up

  • If the rug is removable, take it outside, shake and air it out for as long as is practical.
  • The first time you vacuum on installed carpet after the clean-up, shut the door to the room or close off the area as much as possible and ventilate the room by opening the windows and doors to the outside. When the vacuuming is done, remove the bag, wipe the vacuum with a damp paper towel, cloth or disposable wet wipe, and then place the vacuum bag and paper towel in a sealed plastic bag outside.  In the case of a canister vacuum, wipe the canister out with a wet paper towel and dispose of the towel as outlined above. Continue to ventilate the room for 15 minutes once the vacuuming is completed.
  • Immediately place waste material outside of the building in a protected area away from children.
  • Do not dispose of the waste in your household trash. Dispose of the waste at a household hazardous waste location as soon as possible.  For more information on the proper disposal of a CFL, visit the City of Guelph's Household Hazardous Waste site.
  • Wash your hands after storing and disposing of waste.

For more information about CFL safety, please visit Health Canada's website.


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