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Mercury Thermostat Precautions and Disposal

Traditionally, thermostats used in residences,businesses and industrial settings, including thermostats sold as stand-alone units and as components within heating and cooling equipment have contained mercury.  As the fall turns to winter, and spring turns to summer, many people think about upgrading their heating system in preparation for winter or summer, including replacing old thermostats.

If your old thermostat contains a mercury switch - it is vital that it is disposed of properly. 

Do not throw the old thermostat in the trash!  Dispose of it properly (more info below).

Each mercury thermostat has an average of 4 grams of mercury in it, which could pollute a typical 80-acre lake or a volume of 20 million gallons of water enough to result in a fish consumption advisory for a year.  It is said that thermostats are the single largest source of mercury in our homes and businesses.  Mercury can hurt humans just as it can pollute the environment.  Medical experts have found that mercury can cause sensory impairment (vision, hearing, speech), disturbed sensation, lack of coordination, loss of hair and teeth and in some extreme cases death. 


How do I know if my thermostat contains mercury?

If you remove the cover from the front of your thermostat - you shoud be able to see the mechanics/wiring inside.  You should also be able to spot mercury switches as shown in the illustration below.  These will look like clear glass tubes containing some silver liquid.  This 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. Because of its excellent conductivity and high surface tension, the mercury rolls freely inside the glass tube of a mercury switch. As it moves within the switch, the mercury breaks or makes electrical circuits, which signal the call for heating or cooling from a furnace or air conditioner.

Is my mercury thermostat safe?

Yes, mercury-containing thermostats are safe. In normal use, the consumer is never exposed to the mercury, which is entirely contained in a glass bulb. Thermostats are specifically designed to protect and hold the mercury inside.  The bulb is protected by a sturdy thermostat casing. Nevertheless, it's 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 makes a mercury free version of the old round thermostat - the T87N . There is also a heat only version of the Honeywell round thermostat that contains no mercury.

I'm not interested in a fancy digital thermostat  - I'd like a simple mechanical thermostat that does not contain mercury.  What is available?

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

Does my digital thermostat contain mercury?

No - if you have a thermostat with a digital readout - it probably does not use a mercury switch.

What do I do with my old thermostat?

See below.

Disposing of thermostats containing mercury

The safest way to dispose of mercury is to take it to a recycling center or a center that will dispose 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 the ground water.  Again DO NOT  throw away your old thermostat.  There may be a program your state where thermostats are professionally disposed of or exchanged.  The US Enivronmental Protection Agency (EPA) has established a list of entities within each state established to help with mercury recyling or disposal.  Click link below:

Local Centers for Mercury Disposal

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

After proper disposal of your thermostat you can upgrade to a new, digital or mercury free mechanical thermostat. It is easier to replace a thermostat that you might think.  If you aren't comfortable doing the replacement yourself.  You can hire an Zibby Mechanical Services to do the work.