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Mercury Thermostat Precautions and Disposal
Posted 5/20/2008

Many thermostats used in residences, businesses and industrial settings all used to contain mercury at one point. When the seasons change many people start thinking about upgrading their heating and cooling systems, which typically means replacing their old thermostats with new ones.   

Do NOT throw your old thermostat in the trash if it contains a mercury switch!  You should dispose of it properly

Each mercury thermostat has an average of 4 grams of mercury in it. This seemingly small amount could pollute an 80-acre lake or 20 million gallons of water and result in a fish consumption advisory lasting a year. Research has shown thermostats are the single largest source of mercury in our homes and businesses. It's important to note mercury can hurt humans just as easily as it can pollute the environment. Talk about a double-edged sword. Medical experts have discovered mercury poisoning causes sensory impairment (i.e., vision, hearing, speech), disturbed sensation, lack of coordination, loss of hair and teeth, and in some cases death.  


How do I know if my thermostat contains mercury?

When you remove the cover from the front of your thermostat you should be able to see the mechanics and wiring nestled inside. You should also be able to spot mercury switches similar to those shown in the illustration below. These will look like clear glass tubes containing a silver liquid. This metallic looking liquid is mercury.


How does the mercury work inside a thermostat?

Mercury's unique characteristics make is extremely effective as a switch in a thermostat. Due to its excellent conductivity and high surface tension, mercury is able to roll freely inside the glass tube of a mercury switch. The mercury "breaks" electrical circuits as it moves within the switch, which then signals the need for heating or cooling from a furnace or air conditioner.

Is my mercury thermostat safe?

You'll be relieved to know thermostats containing mercury are indeed safe. When used properly, the consumer is never exposed to the mercury since it's safely contained inside a glass bulb. Thermostats are specifically designed to protect and hold the mercury inside this container. The bulb is also protected by a sturdy thermostat casing. Nevertheless, it's always prudent to handle thermostats with care.

I'd like to replace my thermostat, but I like my old round Honeywell thermostat. Is there a round Honeywell thermostat that does NOT contain mercury?

Yes, Honeywell does make a mercury free version of the old round thermostat. It's known as the
 T87N . There is also a heat only version of the Honeywell round thermostat that doesn't contain mercury for those interested.

I'm not interested in a fancy digital thermostat. I'd like a simple mechanical thermostat that doesn't contain mercury. What are my options?

Both Honeywell and White-Rodgers have introduced classic looking
 mechanical thermostats, with no mercury that have styling similar to older residential thermostats.

Does my digital thermostat contain mercury?

If you have a thermostat with a digital readout, then it probably doesn't use a mercury switch.

What do I do with my old thermostat?

See below.

How to Properly Dispose Thermostats Containing Mercury

The safest way to properly dispose of mercury is to take it to a recycling center or facility that disposes of heavy metals or other toxins. Whatever you do, DO NOT pour mercury down your drain!!!  Mercury can leech out of your pipes and enter local ground water. 

Again, DO NOT throw your old thermostat in the trash if it contains a mercury switch. There may also be a program in your state where thermostats are professionally disposed or exchanged. The U.S. Environmental Protection Agency (EPA) has established a list of entities within each state established to help with mercury recycling or disposal. Click the link below to learn more.

Local Centers for Mercury Disposal 

If you can't find what you need on the EPA's website, you should contact your county or state environmental office or solid waste office for services available in your area.

After properly disposing your old thermostat you can upgrade to a new, digital or mercury free mechanical thermostat. Replacing a thermostat is easier than you may think. But if you aren't comfortable doing the replacement yourself, you could always hire a Heating, Ventilation, and Air Conditioning (HVAC) contractor to do the work for you. 

Find your new thermostat today using our thermostat finder utility. You can find a wide variety of mercury free thermostats to fit you heating and cooling needs in just a few simple steps.