Mercury in Thermostats

If you are a household, the Earth 911 website should direct you to the nearest household hazardous waste collection location. DTSC suggests you verify that the facility accepts mercury thermostats before you take them to the facility.

A listing of household hazardous waste collection facilities is also available and is sorted by city. The Thermostat Recycling Corporation (TRC) also maintains a list of thermostat collection points. Please refer to the Universal Waste Regulations for information on how to properly manage your unwanted mercury thermostats. TRC is a non-profit corporation voluntarily founded by thermostat manufacturers for the purpose of collecting and properly disposing of mercury-containing thermostats.

Many thermostats sold prior to 2006 contain a mercury switch, which consists of a glass tube with mercury inside. Mercury’s unique characteristics make it 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 opens and closes an electrical circuit, which turns on and off a furnace or air conditioner to maintain a desired room temperature.

Try to keep the cover attached to the thermostat to prevent accidental breakage and the release of mercury during storage or transport. If a collection location or HVAC contractor has loose bulbs, the collector can contact TRC at trc@thermostat-recycle.org and TRC should assist the collector in the proper disposal of the bulbs. Generally TRC only accepts whole mercury-switch thermostats with the cover attached due to the potential for breakage in transport to the recycling facility.

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

In normal use, mercury-containing thermostats are safe; the consumer is not exposed to the mercury, which is sealed inside a glass bulb. Mercury thermostats were designed with a sturdy casing to hold and protect the sealed glass bulb inside. Nevertheless, it’s prudent to use mercury thermostats with care.

California law bans the disposal of mercury-containing thermostats in municipal trash. Be sure your technician or contractor properly removes and manages your thermostats in accordance with California’s Universal Waste Regulations.

The intact thermostat, including the cover, should be taken to the nearest collection center. The thermostat casing protects the mercury switch during transportation. Thermostat manufacturers have provided collection bins to approximately 600 household hazardous waste facilities and wholesalers who sell new (non-mercury) thermostats and HVAC equipment.

California law has prohibited the sale of mercury thermostats since 2006, but there is no requirement that you replace your existing mercury thermostat. If you do decide to remove a mercury thermostat (e.g., you plan to replace it with an energy-efficient programmable model, you are upgrading your HVAC system, or you plan to demolish the building), you need to manage the unwanted mercury thermostat properly, in accordance with California’s Universal Waste Regulations.

No. There are several thermostat technologies that do not use mercury. These include electronic, snap-action, reed switch, and vapor-filled diaphragm thermostats. Since California’s ban on sale of mercury-added thermostats took effect in 2006, mercury thermostats have been supplanted by these mercury-free types.