How-to · 4 min read · Updated 6 November 2026
Mercury spill in a dental practice: what to do step by step
How spills happen in modern practices
Most practices no longer handle bulk mercury, as amalgam has been required in pre-dosed capsules since 2019. Spills are therefore usually small: a capsule that leaks or breaks in the mixer, dropped amalgam, a broken old mercury thermometer or sphygmomanometer, or old stock found during a clear-out. Small spills are manageable with a spill kit, but they still need to be dealt with properly because mercury vapour is toxic and droplets spread easily. Metallic mercury gives off vapour at room temperature, and the vapour has no smell, so the absence of any odour does not mean the area is safe.
Step by step: dealing with a small spill
- Stop work and keep patients and other staff away from the area
- Open windows and turn down heating where possible, as warmth increases vapour
- Remove watches and jewellery, especially gold, which mercury can damage
- Put on the gloves and apron from the spill kit
- Collect visible droplets with the kit's scoop, syringe or mercury sponge, working from the outside in
- Use the amalgamating powder in the kit on any remaining fine droplets, following the instructions
- Place all recovered mercury and contaminated materials in the kit's sealed container
- Check shoes, clothing and nearby surfaces for droplets
- Label the container and store it with your amalgam waste for collection
- Record the spill and review what caused it
What not to do
| Do not | Why |
|---|---|
| Use a vacuum cleaner | It heats and spreads mercury vapour and contaminates the vacuum |
| Sweep with a broom | It breaks droplets into smaller beads that spread further |
| Pour mercury down a drain or sink | It contaminates pipework and the environment |
| Put it in clinical waste bags | Mercury must not be incinerated as clinical waste |
| Use household cleaning products on it | Some react with mercury or spread it |
| Walk through the spill area | Droplets are carried on shoes to other rooms |
What a mercury spill kit should contain
- Disposable gloves and an apron
- A scoop or spatula and a syringe or aspirator for collecting beads
- Mercury absorbent sponges or alloy wool
- Amalgamating powder to bind fine droplets
- A sealable, shatterproof waste container
- Instructions and labels
Keep the kit where amalgam is mixed or stored, check it regularly, and replace it after use. Staff who handle amalgam should know where it is and how to use it.
Include spill procedures in induction for new clinical staff and in your COSHH assessment for mercury. A short practical demonstration, using the kit's instructions, makes a real difference to how calmly and safely a spill is handled when it happens.
Larger spills and spills on carpet
A larger spill, for example from old bulk mercury or a broken container, may be beyond what a basic kit can handle. Evacuate and ventilate the room, keep it closed to others and seek specialist help. Mercury that falls into carpet, gaps in flooring, sink traps or cracks is very hard to recover, which is one reason clinical areas should have impervious, sealed flooring with coved edges. Contaminated carpet or flooring may need to be removed and disposed of as mercury-contaminated waste.
After the spill
Record what happened, roughly how much was spilled, where, who dealt with it, what protective equipment was used and what was done with the waste. Review your COSHH assessment for mercury and amalgam, check whether the cause was equipment such as a faulty mixer or capsule, and refresh staff training. If anyone is worried about exposure, refer them to occupational health. Make sure the spill waste is included in your next amalgam collection and listed on the consignment note. If the spill was caused by faulty equipment, take it out of use until it has been checked or replaced, and tell the supplier.
Preventing spills
Most spills are preventable with simple habits and well-maintained equipment.
- Use only pre-dosed capsules and check them for damage before mixing
- Keep the amalgamator lid closed and well maintained
- Store amalgam waste in sealed containers away from heat
- Remove old mercury thermometers and sphygmomanometers and dispose of them properly
- Clear out any remaining bulk mercury through your waste contractor
Frequently asked questions
Can you vacuum up mercury from a dental spill?
No. A vacuum cleaner heats mercury and spreads its vapour through the exhaust, and it contaminates the vacuum itself, which then has to be disposed of as mercury waste. Use the mercury spill kit to collect droplets with a scoop, syringe or sponge, and use amalgamating powder for fine residue. Ventilate the room well while you work and afterwards.
Where does mercury from a spill kit go?
The sealed container from the spill kit, with the recovered mercury and contaminated materials, goes in the amalgam and mercury waste stream for collection by a hazardous waste carrier. It must not go in clinical bags, sharps containers or general waste. Make sure it is listed on the consignment note when it is collected, and keep the spill record with your COSHH and waste files.
Does every dental practice need a mercury spill kit?
Any practice that uses, stores or removes amalgam should have a mercury spill kit available and staff trained to use it, as part of managing mercury risks under COSHH. Keep the kit near where amalgam is mixed or stored, check it regularly and replace it after use. Practices that never use amalgam should still consider whether old stock, old mercury equipment or amalgam in pipework from previous occupants is present.
mercury spill spill kit COSHH amalgam
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