Thermometers and Thermostats

Thermometer

The term thermometer applies to instruments that measure temperature. Various types exist on the market, for a multitude of purposes, and can be found in households, laboratories, medical facilities, industries, and schools. Mercury has traditionally been used in thermometers since it expands and contracts consistently with temperature. Held within a bulb at the base of the instrument, mercury is free to move up and down a capillary tube where its position can be associated with a specific temperature.

ThermometerMercury may be found in fever, basal, scientific, industrial and cooking thermometers. Thermometers containing mercury can be easily identified by the colour of the material in the bulb.

Digital or spirit-filled (red) thermometers are a safer alternative. Infrared (ear) thermometers may be used as an alternative to mercury fever thermometers. Recently, thermometers containing gallium, indium, and tin, have become available as a mercury-free alternative.

Useful Information:

Proposed Risk Management Instruments for Mercury-Containing Products

Some pharmacies have stopped selling mercury thermometers and may offer a thermometer take-back program.

 

Below you will find descriptions of thermometers, such as fever thermometers, industrial thermometers and laboratory thermometers:


Fever Thermometers

Use: Fever thermometers measure human body temperature including oral, rectal, or auxiliary (armpit). Fever thermometers are common place in homes and medical institutions, however sales of mercury-containing fever thermometers have been decreasing as alternatives increase in popularity.

Description: The term "thermometer" applies to instruments that measure temperature. Various types, for a multitude of purposes, exist on the market and can be found in households, laboratories, industries, and schools. The mercury is held within a bulb and is free to move up and down a capillary tube. Because mercury expands and contracts consistently with temperature, its position in the capillary tube can be associated with a specific temperature.

Identification: Mercury may be in fever, basal, and cooking thermometers. Thermometers containing mercury can be easily identified by the colour of the material in the bulb. If the bulb is silver, the thermometer most likely contains mercury. New fever thermometers containing gallium, indium, and tin are an exception to this as they will also appear silver in color. These thermometers are marketed as "mercury-free" thermometers and will probably be clearly marked as such. If the bulb is any other colour, e.g. red or blue, it is most likely spirit-filled.

Mercury content: Content ranges from 0.5 to 3 grams.

Alternatives: Mercury-free alternatives include digital, alcohol, and glass gallium-indium-tin thermometers. Other alternatives include ear canal thermometers and flexible forehead thermometers. These alternatives can be as accurate as mercury thermometers, and in many cases are easier to read. If mercury-containing thermometers are essential, buy Teflon-coated ones to minimize the release of mercury in case of an accidental breakage.


Industrial Thermometers

Use: Industrial thermometers are commonly found in mechanical rooms. Common uses include climate control in heating, ventilation, and air conditioning (HVAC) systems.

Description: Industrial thermometers are usually manufactured with a probe that is inserted into a source of heat or cold. The probe is directly connected to a sensing medium, such as mercury, that in turn displays a reading on a calibrated scale.

Identification: Industrial mercury-containing thermometers are generally distinguishable by a silver-coloured column. Mercury-containing thermometers are sometimes misidentified as alcohol-filled thermometers because an optical illusion causes some mercury-filled thermometers to appear to have a red column. Care should be taken to look closely at the column and column size. Mercury-containing thermometers are generally thinner than alcohol-filled thermometers. These devices are often found attached to piping systems, boilers and commercial hot water heaters.

Mercury content: The average mass of mercury used in an industrial thermometer is 5 grams.

Alternatives: Alternatives include alcohol-filled, organic-based replacement-fluid-filled, and digital thermometers.


Laboratory Thermometers

Use: Laboratory thermometers are used in laboratories to measure temperature. They are most accurate when semi-immersed or totally immersed in the medium being measured. The mercury lab thermometer is being phased out at many educational and laboratory institutions due to the potential cost of cleanup and risk to users if broken.

Description: Laboratory thermometers are long-stemmed with a silver bulb at the end. Mercury located in the bulb expands with increasing temperature and contracts with decreasing temperature. The temperature is measured by reading the level of mercury on a calibrated scale.

Identification: Lab thermometers are distinguished by the long stem and elongated bulb at the end. A silvercoloured liquid generally denotes mercury. Other coloured liquids are not mercury.

Mercury content: The average mass of mercury in a laboratory thermometer is around 5 grams.

Alternatives: Mercury-containing laboratory thermometers are easily replaced with alcohol-filled or organic-based replacement fluid-filled thermometers. Digital laboratory thermometers are equally desirable and in many cases are easier to read.


Thermostats

Use: Mercury-containing thermostats may be used in heating and cooling systems in residential, medical, commercial and industrial settings.

Description: Thermostats comprise a tilt switch with a mercury ampoule used to activate or deactivate the heating or cooling device.

ThermostatIdentification: Thermostats are typically mounted on walls, usually at chest height. Most non-digital thermostats contain mercury. Thermostats that contain mercury can usually be identified by carefully removing the front plate of the device and visually inspecting the uncovered components. If there are glass ampoules inside that contain a silver liquid, it is most probably mercury.

Mercury content: Ampoules generally contain 3 grams of mercury. There may be one to six ampoules depending on the model and application of the thermostat (Sustainable Hospitals Project, 2003).

Alternatives: Alternatives include programmable mercury-free electronic thermostats. A programmable thermostat automatically sets back temperature in a room or building according to a predetermined schedule, whereas non-programmable thermostats maintain constant room temperature 24 hours per day. Mercury containing thermostats can normally be replaced by electronic alternatives. One advantage of electronic devices is that they can result in energy savings.

ThermostatUseful Information:

Switch the 'Stat Program

Proposed Risk Management Instruments for Mercury-Containing Products

For more information about other types of switches, please see the switches description.