Mercury-containing thermometers are being phased out across the United States in an effort to rid the environment of the neurotoxin. Mercury, the only metal that is liquid at room temperature, winds up in our oceans, where it contaminates large food-fish preferred by humans. This is the main source of mercury poisoning in humans.
The U.S. Environmental Protection Agency has mercury thermometer-related questions and answers posted on its website, as well as videos about industrial alternatives. Here is a sampling of what you'll find.
Q. Why are mercury thermometers being replaced?A.Mercury is a neurotoxin and harmful to human health and the environment. Several states prohibit the sale of mercury-containing thermometers.
Q. Will the replacement of mercury thermometers be problematic?
A.For most applications, alternatives to mercury-containing thermometers are available. However, there are certain applications where the use of alternatives to mercury-containing thermometers is more difficult. One example is the use of thermometers in high temperature devices such as autoclaves; however, this is an application in which mercury is not commonly used. (The website provides "User Friendly Guide on the Replacement of Mercury Thermometers" in PDF format on the website.)
Q. What types of non-mercury-containing thermometers are currently available?
A.There are several types, including both liquid-in-glass and electronic digital thermometers. An example of an electronic digital thermometer is the platinum resistance thermometer. Others include the thermistor and the thermocouple. Non-mercury organic-liquid-filled glass thermometers are also a replacement for mercury thermometers.
Q. Are non-mercury-containing thermometers as accurate as mercury-containing thermometers?
A. The non-mercury platinum resistance thermometer is as accurate as mercury-containing thermometers through a wide temperature range. Non-mercury thermistors are accurate but have a limited temperature range. Non-mercury thermocouples are not as accurate as resistance thermometers or thermistors, but are widely used because of their durability. Non-mercury liquid-in-glass thermometers are not as accurate and are typically used when applications call for modest uncertainty requirements.
Q. Are non-mercury-containing thermometers as durable as mercury-containing thermometers?
A.Like a mercury-containing thermometer, the platinum resistance thermometer is sensitive to mechanical shock. Thermistors are less sensitive and thermocouples are very durable. Non-mercury liquid-in-glass thermometers are as durable as mercury liquid-in-glass thermometers.
Q. Are alternative thermometers more expensive than mercury-containing thermometers?
A.Electronic thermometers are typically more expensive than mercury-containing thermometers. However, using non-mercury-containing thermometers avoids the potential cost of mercury spill cleanup and disposal.
Industrial facilities with mercury-containing thermometers must dispose of them with care. They can be:
- Shipped through a hazardous-waste transporter to a
mercury recycling facility.
- Directly shipped as “universal waste” to a mercury recycling
- Disposed of by small businesses at a local collection event, collection facility or destination facilities for “universal waste.”
To see the EPA's full set of mercury-sensor phase-out questions and answers, and to view tutorial videos, go to www.epa.gov/hg/thermometer.htm.