Mercury-Added Thermostat Frequently Asked Questions

Mercury thermostats can be a major source of mercury contamination in the environment. Mercury is a dangerous neurotoxin. It does not break down in the environment and it bioaccumulates in the tissues of fish, which are then consumed by people. Each mercury thermostat contains about 3 grams of mercury. One gram of mercury can contaminate a 20-acre lake.

The Thermostat Care website has a list of mercury thermostat collection locations by county, as well as a map of all the collection locations in California. Their website also contains instructions on how to prepare your thermostat for disposal and information on how to receive a $30 incentive for properly disposing of a mercury thermostat.

Other resources include the Earth 911 website, which should direct you to the nearest household hazardous waste collection location. The Thermostat Recycling Corporation (TRC) also maintains a list of thermostat collection points. TRC is a non-profit corporation founded by thermostat manufacturers.

A mercury-added thermostat is a product or device that uses a mercury switch to sense and control room temperature through communication with heating, ventilating, or air-conditioning equipment. As it moves within the glass switch, the mercury opens and closes an electrical circuit, which turns on and off a furnace or air conditioner to maintain a desired room temperature. Prior to 2006, when mercury-added thermostats were banned for environmental health and safety reasons, many thermostats contained mercury.

No. Mercury-added thermostats were banned in California in 2006. Thermostats manufactured since 2006 do not contain mercury. For this reason, thermostats in older homes and buildings are more likely to contain mercury. When replacing an older thermostat, it is important to dispose of it properly. The Thermostat Care website has guidelines for proper disposal of mercury thermostats. When replacing a mercury-added thermostat, the four basic types of thermostats you will encounter are: non-programmable, programmable, Wi-Fi and smart thermostats. Local utility companies may offer rebates for qualifying smart thermostats, so check their websites for more information.

Importantly, thermostats should be returned intact when possible. Do not remove the mercury switch. However, if you already have loose bulbs, try to keep the cover attached to the thermostat to prevent accidental breakage and the release of mercury during storage or transport. Any loose bulbs should be placed in a sealed, labeled container. Check with the collection location in advance to ensure they are  prepared to accept loose bulbs..

Fully intact mercury-containing thermostats are safe. As long the mercury remains sealed in the glass bulb, and the glass is protected by the thermostat cover, the consumer is unlikely to be exposed to mercury. It is important to handle mercury thermostats with care and dispose of them properly so that the sturdy casing, and the sealed glass bulb inside, remains intact.

California law bans the disposal of mercury-containing thermostats in municipal trash. The Mercury Thermostat Collection Act of 2021 requires a qualified third party to establish convenient collection locations for out-of-service mercury-added thermostats. Go to the Thermostat Care website to find the collection location nearest you. When possible, leave the thermostat intact, including the cover.

California law prohibited the sale of mercury thermostats in 2006, but there is no requirement that households replace existing mercury thermostats. A person who handles out-of-service mercury-added thermostats (and ampoules removed from thermostats) must manage the thermostats in a way that prevents releases (e.g., of mercury) to the environment. Anyone who removes out-of-service mercury-added thermostats from a building is required to handle and transport mercury thermostats in accordance with universal waste regulations.

You may contact the Department of Toxic Substances Control at thermostats@dtsc.ca.gov or at (800) 72-TOXIC ([800] 728-6942) for answers to your questions on the Mercury Thermostat Collection Act of 2021 and for information on the Universal Waste Regulations for handling thermostats.