Sources of Mercury in Industrial Facilities

The following is intended to be a guide for industrial facilities (non-mercury processing) to identify where potential sources of mercury may be found within the facility in order to encourage proper handling and elimination of the toxic material.

Other sources of mercury that may enter the environment, such as health care (blood pressure cuffs, etc.) including dental care are major sources of mercury into the environment. However they are omitted from this directory, as they are not commonly found in an industrial facility.

Auto Brakes
  • ABS Breaking Systems*
Auto Switches
  • Hood Lighting*
  • Trunk Lighting*
  • Collision Sensors
  • Acceleration sensors for air bags and seatbelts
  • Tilt switches
  • Heated car rear windows
  • Alkaline-manganese batteries
  • Zinc-carbon batteries with mercury added
  • Button cell mercuric-oxide batteries
Battery chargers
Bilge Pumps
CRT’s – Cathode Ray Tube
Central clocks and time clocks
Circuit breakers
Dishwashers / Parts Washers (electrical switches)
Door bells ("ding-dong")
Dyes & Pigments
Electronics with Liquid Crystal Display (i.e. cameras, camcorders, etc.)
Electrical Distribution Boxes
Float switches and level meters
Flow meters
Freezers (automatic lights)*
HVAC Equipment
  • Central Air Conditioning Units
  • Gas Ovens – Flame sensor contains mercury
  • Electric Ovens – Flame sensor contains mercury
Interlock switches
Laboratory Reagents
  • Neon Lights
  • High Intensity Discharge (HID)
  • Mercury Vapor Lights
  • Fluorescent Lamps
  • Metal Halide Lamps
  • High Pressure Sodium Lamps
  • Ultraviolet Lamps
Lifts for disabled
Measuring and control instruments
Microwave Ovens
Paint Additives (suspended in 1991)*
Pesticide Additives*
Preservative for human and animal medical products – vaccines, etc.
“Rubber” Flooring (the type frequently used in gyms and sports facilities in the 1970’s)*
Signal alarms
Skylifts (leveling)
Sprinkler Systems (Old)*
Sump Pumps
Time switches/landing switches
Transformers (gas-operated relays)

* Mercury is no longer added. Mercury may be found in older materials and goods.

Manufacturing Processes That Use Mercury

Chlorine Production
Portland Cement
Mining – i.e. gold mining
Caustic Soda
Sulfuric Acid

Industries Using or Emitting Significant Amounts of Mercury

Power Generation
  • Dental Care

Common Uses for Mercury

Some common uses for mercury are to conduct electricity, measure temperature and pressure, act as a biocide, preservative, and disinfectant, as well as a catalyst for reactions. Within industry there are all possible types of mercury products installed in distribution boxes, electrical surrounding equipment, boiler rooms, sumps, machinery, measuring instruments, etc. The following provides a brief summary of mercury use in specific industrial products and sources.

Auto Switches
Mercury switches in Hood and Trunk Lighting, Collision Sensors

Automobile truck and hood light switches often contain mercury. If the light goes on when the lid is partially up, or if you can see that the bulb housing is deliberately mounted at an angle to the hood, a mercury switch is probably being used. A variety of manufacturing processes use relays to control power to heater or pumps. Relays that contain mercury switches activate: airbags, anti-lock brakes (primarily found in four-wheel drive vehicles), some seat belt systems, and some automatically adjusting suspension systems. Some agricultural equipment, military vehicles, mass transit vehicles, and fire hook and ladder equipment also contain mercury switches.

Batteries, Mercury-containing
The mercury containing batteries provide a compact and precise voltage source to power metering electronics. Mercuric oxide (mercury zinc) batteries and button batteries are the only batteries made in the United States that may contain added mercury. Mercuric oxide batteries offer a reliable and constant rate of power discharge and can be made in a wide variety of sizes intended for use in electronic devices. New equipment models generally require zinc air batteries. The shelf life of mercuric oxide batteries is up to ten years.

Bilge Pumps
The float switches within the bilge pump may contain mercury.

Boiler rooms
Small boiler rooms often contain tube thermometers and other thermometers. Oil level gauges for remote measurements are also common.

Combustion Sources - Boilers
Combustion sources include utility boilers, medical waste incinerators, municipal waste combustors, commercial/industrial boilers, hazardous waste combustors, residential boilers, wood combustion, sewage sludge incinerators and crematories. Mercury emissions from these sources (excluding wood-fired residential heaters) account for an estimated 125 Mg/yr (138 ton s/yr) or 87 percent of the mercury emissions generated annually in the United States.

Mercury is contained within the fluorescent tubes that provide the source of light in the LCD. Mercury is used the LCD backlights.

No mercury is required in CRT fabrication. Although the quantities of mercury are not large, they cannot be discounted given the toxicity of mercury to both human health and the environment.

Historically mercury has been added to cosmetics as a skin whitening additive. Today, the use of mercury compounds as cosmetic preservative ingredients is limited to eye area cosmetics at concentrations not exceeding 65 parts per million of mercury calculated as the metal (about 100 ppm or 0.01% phenylmercuric acetate or nitrate) and provided no other effective and safe preservative is available for use. Mercury compounds are readily absorbed through the skin on topical application and have the tendency to accumulate in the body. They may cause allergic reactions, skin irritation or neurotoxic manifestations."

Dishwashers / Parts Washers (electrical switches)
Temperature gauges and various mercury containing switches are installed in industrial parts washers.

Distribution boxes and electric installations
Mercury is often found in relays located in distribution boxes in buildings, e.g. for regulating stair lights.

District heating plants and furnace rooms
Large housing estates and industrial areas often have a central heating plant with flue-gas meters, tube thermometers, thermostats, pressure switches, oil level gauges, flow meters, etc.

Drains and old waste pipes
In dental surgeries and other premises where mercury is used, amalgam and metallic mercury can have collected in waste pipes, leaching mercury into the sewerage.

Dyes & Pigments
Mercury sulfide has been incorporated into organic pigments used to make paints and inks. The mercury is primary found in the red (vermilion) color family.

Printed circuit cards in electrical components in machinery and equipment can contain mercury. Companies specializing in dismantling electronic equipment will handle this in an environmentally safe way.

Float Switches and Level Meters
Float switches are used in sump pits, factories and sewage plants to maintain a given level of liquid. The float switch is a round or cylindrical float with a switch attached to it. The switch keeps the circuit closed until the float reaches a certain height. Then, the mercury slides down, opening the circuit and shutting off the pump.

Flow Meters
Flow meters are used for measuring liquid (water, product) flow. Some flow meters contain large quantities of mercury - 5 kilograms and more.

Freezers and refrigeration equipment may have mercury switches in the internal lid light within the light socket. If a chest freezer has a light in the cover and no visible mechanical switch, then it contains a mercury switch. This device senses when the lid is raised and turns on the light.

At one time mercury chloride was one of the active ingredients used in fungicide chemicals.

Gauges: Manometers, Barometers, & Vaccum Gauges
Many barometers and vacuum gauges found in machinery contain mercury. Liquid mercury in the gauges responds to air pressure in a precise way that can be read on a calibrated scale. Several mercury-free alternatives are available. Some operate on the same principle as mercury gauges but use mercury-free liquids in the tube.

Needle or bourdon gauges operate under a vacuum with a needle indicator. Electronic gauges can be used to measure pressure, but they must be calibrated with a mercury manometer. Equipment manufacturers recommend that service technicians use a needle or digital gauge to test the systems they are servicing, but that they calibrate the gauges they use in the field with a mercury manometer kept at their shop.

Mercury manometers occasionally need servicing to maintain their accuracy, and elemental mercury often remains as a waste. If the manometer is hard to read because of dirt and moisture in the tube, the mercury needs to be removed and replaced.

Heating & Ventilation equipment (A/C)
Here you can find manometers, thermostats, thermometers, relays, etc. containing mercury.

Flame sensors in furnaces may contain mercury. The metal flame sensor consists of a metal bulb and thin tube attached to a gas-control valve. The mercury is contained inside the tube and expands or contracts to open and shut the valve.

Gas meters installed before 1961 contain a mercury regulator attached to the gas meter.

Several types of gas-fired appliances that have pilot lights, like ranges, ovens, clothes dryers, water heaters, furnaces, and space heaters use mercury-containing flame sensors.

Interlock Switches
Mercury switches consist of a mercury filled tube with electrodes at each end. When the tube is tilted the mercury flows to either end cutting off the circuit on one end while opening it on the other side. They often function as on/off switches.

Industrial Chemicals
Caustic Soda
The majority of sodium hydroxide (caustic soda) is commercially produced through electrolytic cell processing. The balance is produced through chemical processes. The electrolytic cells used to make the caustic soda contain mercury.

Laboratory Reagents
Mercury is used as a preservative in laboratory reagents and related chemicals. In laboratories, hospitals, and schools mercury has been used as a reagent for different analyses, as well as in thermometers and other measuring instruments.

Lamps - Fluorescent & High-Intensity Discharge (HID) Lamps
Fluorescent and HID lighting is an excellent business and environmental choice because they can use up to 50 percent less electricity than incandescent lighting. However, used fluorescent lamps, mercury vapor lamps, metal halide lamps, high pressure sodium lamps, and neon lamps must be managed properly because they contain mercury. Some HID lamps may also be hazardous due to lead content, primarily due to the use of lead solder.

Disposal Options for Mercury Containing Lamps:
Businesses should manage and dispose of mercury-containing lamps as universal wastes, for which the regulatory requirements are much simpler than hazardous wastes.

Mark the lamp storage area with the words "Fluorescent lamps for recycling". Do not break or crush lamps because mercury may be released. If lamps are accidentally broken, store them in a sealed container. Pick up spilled powder and add it to the sealed container. Arrange with a lamp transporter to pick them up.

Lifts for Disabled
Various electrical switches contained in the lift mechanism contain mercury.

Machinery and equipment
A number of types of machinery and equipment can contain mercury, e.g. level indicators in skylifts and mobile ladders, industrial welding equipment, forestry machinery, gas-operated relays in transformers, manufacturing machinery, etc.

Mercury switches are found in a variety of items ranging from chest freezers to sump pumps. Mercury-containing tilt switches are found in or under the lids of clothes washers and chest freezers. They stop the spin cycle or turn on a light. They are also found in motion sensitive and position-sensitive safety switches in clothes irons and space heaters. If a mechanical switch is not visible in these items, a mercury switch is probably being used. Float switches are commonly used in sump pumps and bilge pumps to turn the equipment on and off when the water is at a certain level. These switch devices are often visible.

Measuring & Control Instruments
In a mercury or alcohol thermometer the liquid expands as it is heated and contracts when it is cooled, so the length of the liquid column is longer or shorter depending on the temperature. Modern thermometers are calibrated in standard temperature units such as Fahrenheit or Celsius.

Paint Additives
Mercury sulfide has been incorporated into organic pigments used to make paints and inks. The mercury is primary found in the red (vermilion) color family. (Suspended in 1991)

Methyl mercury is a key ingredient in pesticides and fungicides used to treat grains and seeds.

Mercury is used as a preservative fro human and animal medical products, i.e. vaccines, etc.

Rubber Flooring
The type frequently used in gyms and sport facilities in the 1970’s. Rubber flooring installed in gymnasiums during the early 1970s contained a mercury catalyst (i.e. 3M Brand Tartan Track, and other brands).

Thermostat Probes
Mercury-containing thermostat probes may be found in several types of gas-fired appliances that have pilot lights, such as ranges, ovens, clothes dryers, water heaters, furnaces, or space heaters. The metal probe consists of a metal bulb and thin tube, referred to as an ampule, attached to a gas-control valve. The mercury is inside the tube and expands or contracts to open and shut the valve. Although non-mercury thermostat probes have been used in these appliances, you should treat all probes as though they contain mercury, unless you know that they do not.

Mercury thermostat probes, also known as flame sensors or gas safety valves, are most commonly present as part of the safety valve that prevents gas flow if the pilot light is not lit. In this application the bulb of the thermostat probe projects into or near the pilot light. These are commonly present in gas ovens and may be present in any other appliance with a pilot light. A mercury thermostat probe may also be present as part of the main temperature-controlling gas valve. In this application, the probe is in the air or water that is being heated and is not directly in contact with any flame. These are typically found in older ovens, clothes dryers, water heaters, and space heaters.

Level indicators switches containing mercury in skylifts

Sprinkler Systems (Old)
Many of the pressure gauges on these older systems contain mercury.

Sumps and tanks
In low-lying areas in buildings, for example, you may find pumping equipment regulating the water level with sender level switches that can contain mercury. Tanks and cisterns can also have switches containing mercury.

Switches – Tilt switches, volumeters, time switches, landing switches
Mercury is contained in temperature-sensitive switches and mechanical tilt switches. Mercury tilt switches are small tubes with electrical contacts at one end of the tube. As the tube tilts, the mercury collects at the lower end, providing a conductive path to complete the circuit. When the switch is tilted back, the circuit is broken. Reed switches are small circuit controls that are used in electronic devices. Their electronic contacts are wetted with mercury to provide an instantaneous circuit when the switch is closed and then an instantaneous current interruption when the circuit is broken.

Thermostats, Thermometers
Mercury-containing tilt switches have been used in thermostats in homes and offices for more than 40 years. They provide accurate and reliable temperature control, require little or no maintenance, and do not require a power source. However, each switch contains approximately 3 grams of mercury.

Mercury-free thermostats are available. Electronic thermostats, for example, provide many of the same features as mercury thermostats. Both types can be programmed to lower room temperatures at pre-set times. This results in fuel cost savings and the environmental benefits from burning less fuel.

Mercury arc rectifiers within electrical transformers operate based on an arc between a pool of mercury and a metal anode that only allows current to pass in one direction. Multiple anodes are typically used, fed from a multiple-phase transformer, the arc jumping from the cathode pool to each anode in sequence. There may be three, six or even twelve transformer phases, each feeding one anode.


MSDS of Mercury

Mercury Containing Equipment Checklist

What Devices Contain Mercury?

Mercury in Goods and Products

NEWMOA Mercury Products Database

Conducting an Internal Mercury Audit for Manufacturing Facilities

Mercury Study Report to Congress
December 1997

Sources of Mercury

Automobile Industry Major Source Of Toxic Mercury Pollution

Binational Toxics Strategy — Mercury Sources and Regulations, 1999 Update

BTS 1999 Update – Appendix B

Mercury Workgroup – Mercury Management Guidebook

National Wildlife Federation Mercury Products Guide: The Hidden Dangers of Mercury

Specifying and Sourcing Mercury-Free HVAC and Building Equipment (from INFORM)

Wisconsin Mercury Sourcebook

U.S. EPA/Purdue University Mercury in Buildings tutorial

Mercury Use Tree

A Guide to Mercury Reduction in Industrial and Commercial Settings (from the Delta Institute)

Implementation of the Mercury-Containing and Rechargeable Battery Management Act:

Mercury Reduction – Best Management Practices for Mercury-containing Products in the Hospital - Batteries

Can the lead, mercury, and liquid crystals in computer displays pose health risks?

Organic and Natural Health-Report

Mercury Containing Equipment Checklist

Caustic Soda Manufacturing

Table 1: Automotive Applications of Mercury
Automotive Application Quantity of Mercury
Michigan Mercury Pollution Prevention Task Force, Mercury Pollution Prevention in Michigan, Final Report, April 1996.