The danger posed by a broken liquid-filled thermometer depends entirely on the substance contained within the glass tube. While modern thermometers use liquids that pose minimal health risks, the traditional liquid—elemental mercury—presents a serious hazard if released. Understanding the contents of an old thermometer is the first step in determining the appropriate safety and cleanup response. The presence of a silver liquid demands an immediate and specialized cleanup protocol.
The Specific Hazards of Mercury
Elemental mercury (chemical symbol Hg) is a dense, silvery liquid metal that was once the standard for thermometers due to its consistent expansion properties. A typical fever thermometer contains about 0.5 to 0.6 grams of mercury, which is enough to pose a health risk if mishandled after breakage. The primary danger from spilled mercury is not from skin contact or swallowing, but from inhaling its odorless, invisible vapor. Mercury slowly evaporates at room temperature, and this vaporization increases significantly in warmer environments.
Inhaling mercury vapor allows it to be absorbed through the lungs, where it can travel to the brain and kidneys. Mercury is a known neurotoxin, and chronic exposure can lead to severe neurological symptoms, including tremors, emotional changes, memory impairment, and lack of coordination. Due to these public health risks, the sale and distribution of mercury fever thermometers have been banned or heavily restricted in many regions. While this phase-out has reduced the threat of new mercury thermometers, older devices may still be present in homes.
Understanding Non-Mercury Thermometer Liquids
Modern liquid-in-glass thermometers have replaced mercury with safer alternatives that are easily identifiable by their color. The most common replacement is colored alcohol, typically ethanol or mineral spirits dyed red or blue. Although alcohol is flammable, the small amount in a thermometer is considered non-toxic and poses a low health risk if spilled. If a colored alcohol thermometer breaks, the main concern is minor irritation to the skin or mouth, which can be resolved by rinsing the area.
Another mercury-free alternative is Galinstan, a non-toxic liquid metal alloy of gallium, indium, and tin. Galinstan is silver-colored and can be mistaken for mercury, but it is not toxic if swallowed and poses no inhalation risk because it does not readily vaporize. Its primary drawback is that it tends to stick to surfaces, making cleanup messy, but it is not considered a hazardous material. If a silver liquid is present in a thermometer not labeled “mercury-free,” it is safest to assume it contains mercury.
Immediate Steps for Cleanup and Disposal
Cleaning a broken thermometer requires two distinct protocols based on the liquid inside. If the thermometer liquid is colored, the spill is considered low-risk, and the area should be ventilated by opening a window. The glass fragments and liquid can be collected using paper towels and disposed of in the regular trash, following local guidelines for glass disposal.
If a silver liquid is present, the area must be immediately isolated, and all occupants, including pets, should leave the room. The area should be well-ventilated by opening windows, and the central air conditioning or heating system must be turned off to prevent the spread of mercury vapor. Never use a vacuum cleaner or broom, as this will aerosolize the mercury and increase the concentration of toxic vapor in the air.
Cleanup involves wearing gloves and using stiff paper or cardboard to gently push the beads of mercury together. Smaller droplets can be picked up using sticky tape, such as duct tape, or drawn into an eyedropper. All collected mercury, broken glass, and cleanup materials, including gloves, must be placed into a sealable plastic bag or container and labeled. The contaminated materials must not be thrown into the regular household trash. Instead, the local health department or a hazardous waste vendor should be contacted for proper disposal instructions.
Safer Alternatives for Temperature Measurement
The simplest way to eliminate the risk of a liquid thermometer breaking is to use modern, non-liquid alternatives. Digital thermometers are widely available and use thermistor technology to provide fast, accurate readings. These devices can be used orally, rectally, or under the armpit and are durable, though they contain a small battery that requires proper disposal.
Infrared thermometers offer a less invasive way to measure temperature without physical contact or hazardous liquids. Temporal artery thermometers scan the forehead, while tympanic thermometers measure the temperature inside the ear canal. These devices are faster and safer than traditional liquid-in-glass thermometers, making them the preferred choice for household and clinical use.