Mercury is a dense chemical element with a high surface tension and low viscosity which tends to divide into small droplets. The higher the number of droplets, the greater the surface area will become as well as the amount of vapour released into the atmosphere.

If a small spillage of mercury happens from a broken thermometer or any other minor source, this isn’t a major emergency and generally does not require attendance from emergency services. However, it’s important to clean up the spillage as thoroughly as possible due to the dangers of chronic exposure to mercury vapour over a period of time.

Any business using mercury or equipment that contains mercury, including mercury thermometers, should have the appropriate gear and materials to allow their workers to carefully clean up any form of spillage.

Clean-up and decontamination

Managing mercury spills the right way is very important.

Spillages can remain on floors and surfaces or become trapped in crevices. Using incorrect clean-up methods can result in the mercury being broken into smaller droplets. Heating the mercury will increase the vapour and therefore cause it to spread.

Ordinary vacuum cleaners should not be used, as they won’t trap small particles. Instead the cleaner will break up mercury globules, pushing them into the air. This will greatly increase the level of exposure.

The preferred method of clean-up is the immediate physical removal of the mercury, by first detecting, then closely removing, all visible droplets. When picking up droplets of mercury, take care to avoid skin contact by using:

  • a dustpan, or
  • an aspirator with a capillary tube, a hand-held pipette and a rubber bulb of water pumps, or
  • strips of adhesive tape.

Once the mercury has been collected it should be stored in tightly closed containers, preferably in water or glycerol. The collected mercury can also be recovered and purified for re-use. If disposal is intended, advice should be sought from the Environment Protection Authority.

To assist with decontamination and reduce the vapour hazard, a variety of materials may be used to absorb or react with any remaining traces of mercury. Suitable materials are available in mercury spill kits which can be obtained from laboratory chemical suppliers and should be used in accordance with the directions provided.

Once these materials have been applied and given sufficient time to merge with the mercury, the affected area should be cleaned thoroughly. Once this is done, the collected waste material should be disposed of as hazardous waste.

If the spillage has occurred on carpet, the mercury will disappear into the carpet and there will be no effective cleaning or treatment method available.

After decontamination, the area of the spillage should be surveyed with a suitable mercury analyser to ensure that the area is no longer contaminated and that the level of mercury vapour is within permitted occupational exposure levels.

This inspection can be completed an occupational hygienist.

Mercury usage precautions

Usage of mercury thermometers is undesirable and consideration should be given to alternative methods of temperature measurement, such as digital thermometers or thermocouples.

Where there is no practical alternative, the thermometer should be mounted in a way that avoids accidental breakage, especially ensuring that any part of the thermometer is shielded against unintentional knocks.

The maximum temperature of the thermometer should not be less than the maximum operating temperature of the appliance to avoid the possibility of bursting the thermometer by overheating.

When working with mercury, you should plan for prevention or containment in order to avoid the possibility of the workplace becoming seriously contaminated.