Mercury Use in Thermostats

This Fact Sheet summarizes the use of mercury in thermostats. It is based on data obtained only from the Interstate Mercury Education & Reduction Clearinghouse (IMERC)¹ Mercury-Added Products Database². It covers thermostats used in residences, businesses and industrial settings, including thermostats sold as stand-alone units and as components within heating and cooling equipment. It does not include mercury thermostats used in cooking ranges; those thermostats are covered in the fact sheet entitled, Mercury Use in Gas & Electric Cooking Ranges and Other Cooking Equipment.

Mercury Components in Thermostats

Mercury thermostats use mercury switches to sense and control room temperature through communication with heating, ventilating or air conditioning equipment.

Mercury thermostats contain bimetal coils that contract and expand with room temperature. When the coil contracts or expands it activates the mercury switch which opens or closes a circuit to make the furnace, heat pump or air conditioner turn on or off. A mercury thermostat may contain one or more switches, depending on how many heating and cooling systems it activates.

Amount of Mercury Used in Thermostats

Table 1 presents the amount of mercury used in thermostats. Manufacturers, importers and distributors of mercury-added products may report the amount of mercury used as an exact number, an average with upper and lower bounds, or as a range.

A number of important caveats must be considered when reviewing the data summarized in this fact sheet:

The information does not represent the entire universe of mercury thermostats and therefore underestimates the total amount of mercury reported for this category of products. The states participating in IMERC continuously receive Product Notification Forms from mercury-added product manufacturers, and the data presented in this fact sheet most likely underestimate the total amount of mercury sold in these products.
The data presented summarize mercury in thermostats sold nationwide in the U.S. in calendar year 2001. It does not include products that were sold prior to January 1, 2001.
Reported data includes only mercury that is used in the product, and does not include mercury emitted during mining and/or manufacturing.

Table 1: Amount of Mercury in Thermostats

Mercury-added Component Amount of Mercury in Individual Component (milligrams) Number of Components Manufacturers Reporting

Switch
   275
   > 1,000
   2,200 - 3,000

   1
   1
   1-6

Invensys Climate Controls
Marvair
Watson McDaniel
PSG Controls
General Electric Company
Heat-Timer
Honeywell, Inc
White-Rodgers
TPI Corp.
Lux Products

Total Amount of Mercury in Thermostats

The total amount of mercury in thermostats sold in the U.S. during calendar year 2001 was 28,689 pounds (13,010,939 grams) or 14.3 tons. This amount under-reports the true amount of mercury sold in thermostats in 2001 because one manufacturer of the mercury switches used in thermostats referred the total amount of mercury to the component manufacturer, Comus International. We are unable to separate this exact switch from the switch types reported by Comus.

Mercury Product Phase-Outs

Marvair discontinued its line of air conditioning units with mercury thermostats in December 2003.

¹ The Interstate Mercury Education & Reduction Clearinghouse (IMERC) was established by state environmental officials from Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont to help them implement laws and programs aimed at getting mercury out of consumer products, the waste stream, and the environment. Washington State officially joined IMERC in 2003. IMERC is a program of the Northeast Waste Management Officials' Association (NEWMOA). In 2001 the NEWMOA member states launched IMERC to provide:

ongoing technical and programmatic assistance to states that have enacted mercury education and reduction legislation
a single point of contact for industry and the public for information on mercury-added products and member states' mercury education and reduction programs

NEWMOA's staff provides logistical, facilitation, and technical support for the activities of IMERC.

² The Mercury-added Products Database contains information on the amount and purpose of mercury in products submitted by, or on behalf of, product manufacturers in compliance with laws in the states of Connecticut, Maine, New Hampshire, and Rhode Island. Beginning in 2001, these states required companies manufacturing, distributing, or importing mercury-added products to report certain information on these products. The information is reviewed and approved by an IMERC Notification Committee comprised of representatives from each participating state. The online Mercury-added Product Database and the Notification Forms and Instructions can be found at the following URL: http://www.newmoa.org/prevention/mercury/imerc/notification/

Published in February 2005

Last Modified 06/18/2008