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Chemical collection and stock control for UK schools, universities and hospitals

Zinc powder (CAS 7440-66-6): storage and disposal

Zinc granules and zinc dust turn up in school, college and university stores, often on the same shelf. The dust is the form that matters most, because it can ignite and gives off hydrogen when damp. Its classification as very toxic to aquatic life then decides how any unwanted stock leaves the building.

CAS number
7440-66-6
Form
Solid
Storage class
Flammable
Signal word
Warning
Usual EWC code
16 05 06*
  • Hazardous to the environment pictogramHazardous to the environment

What to do this week

  1. Check the label is readable and write down the opened date if it is not already there.
  2. Check it is stored as flammable stock and apart from the items listed under "Do not store with".
  3. If you no longer need it, add it to your disposal list so it goes on the next collection.

Safe storage in a school or lab

The hazard that decides placement is the dust: fine zinc can ignite and releases hydrogen with damp, acids and alkalis, so it goes with flammable stock rather than on the general shelf. Use a ventilated fire-resistant cabinet with spill containment, away from ignition sources and oxidisers, and keep the lid tight and the contents dry. Keep zinc away from ammonium nitrate, calcium hypochlorite, chromium trioxide and hydrogen peroxide, from iodine, and from carbon disulfide, which reacts violently with it. Picric acid products such as Bouin's fluid and ammonium picrate form shock sensitive picrates with metals. Zinc is also very toxic to aquatic life, so a spill must not reach a drain.

How to tell it has deteriorated

Fresh zinc looks metallic grey and loose. Over time a dull film forms, and in a damp store a white powdery bloom appears on the surface and around the cap. Light dulling is expected. A white crust that binds granules together, or dust that has clumped, shows that moisture has got in. Because damp dust in a sealed container can build pressure, a bulging or tight lid matters more than the colour. Look too for corrosion of a metal cap, label staining, a split seal and a missing stock record. Anything wet, caked or swollen should stay closed and be left where it is until it has been assessed.

How it must be disposed of

By specialist collection only. It never goes down the drain or into general waste. It is normally packed in a flammable laboratory pack with compatible chemicals.

Neither dust nor granules should go down a sink or drain, into a general waste bin or a skip, and nobody should try to react, dissolve or burn the metal away. Zinc is very toxic to aquatic life with long lasting effects, which is why it must never go down a drain. The only route is specialist collection. Expect 16 05 06*, a hazardous entry, with UN 1436 in the description and the hazardous waste consignment paperwork retained for three years afterwards. In a lab pack it is grouped apart from oxidisers, acids and alkalis. Note which form you hold and whether it is dry.

Waste codes and transport details for Zinc powder
EWC code, laboratory chemicals16 05 06*
Discarded inorganic chemical, not a laboratory pack16 05 07*
Hazardous wasteYes

The code depends on where the waste came from and what it is mixed with. Use the waste code finder to see why.

Do not store with

  • OxidiserOxidisers can ignite flammable materials or make a fire far more intense.
  • AcidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • CorrosiveA leak of corrosive stock can break down flammable containers and feed a fire.

Named chemicals to keep apart

  • Acetic acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Ammonium nitrateAmmonium nitrate forms mixtures with these materials that can detonate.
  • Ammonium picratePicric acid forms shock sensitive metal picrates with metals.
  • Calcium hypochloriteStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Carbon disulfideCarbon disulfide reacts violently with these materials.
  • Chromium trioxideStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Hydrochloric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Hydrogen peroxideStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
Show 15 more
  • IodineIodine forms sensitive or violently reacting products with ammonia and reactive metals.
  • Nitric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Picric acidPicric acid forms shock sensitive metal picrates with metals.
  • Potassium chlorateStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Potassium dichromateStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Potassium hydroxideStrong alkalis release flammable hydrogen with these metals.
  • Potassium nitrateOxidisers can ignite flammable materials or make a fire far more intense.
  • Potassium permanganateStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Sodium azideAzides form shock sensitive metal azides with lead, copper, brass and similar metals.
  • Sodium chlorateStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Sodium dichromateStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Sodium hydroxideStrong alkalis release flammable hydrogen with these metals.
  • Sulfuric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Thionyl chlorideA leak of corrosive stock can break down flammable containers and feed a fire.
  • Zinc chlorideA leak of corrosive stock can break down flammable containers and feed a fire.

Common quantities we collect

Usually held as: granules, dust.

Part-used bottles and full containers are both fine. Tell us the size and how many, and an estimate is enough for a first price.

Where it is commonly held

Hazard statements

  • H410 Very toxic to aquatic life with long lasting effects.
Precautionary statements
  • P273 Avoid release to the environment.
  • P391 Collect spillage.
  • P501 Dispose of contents and container in accordance with local, regional, national and international regulations.

Substance as classified, dilutions may differ.

Questions

Is zinc granule stock as risky as zinc dust?

Fine dust is the main concern because it can ignite and releases hydrogen with damp, acids and alkalis. Whichever form you hold, keep it dry and away from acids and oxidisers, and record the form for collection. Both forms are classified as very toxic to aquatic life.

Why is zinc kept in the flammable cabinet when it is a metal?

Fine zinc dust can ignite and gives off hydrogen when damp or in contact with acids and alkalis, so it is stored with flammable stock. Appropriate dry, closed storage helps protect zinc dust from moisture and keeps it separate from incompatible oxidisers and acids.

A zinc tin has a white crust and a tight lid. What should we do?

Leave it closed and keep handling to a minimum. A white crust shows that moisture has reached the metal, and damp dust in a sealed container can build pressure. Keep it in the cabinet, record its condition and send a collection enquiry so it can be assessed.

Guidance only. Check your own risk assessment and your supplier's safety data sheet.

Hazard data source: PubChem GHS Classification, retrieved 31 Oct 2026. Formula Zn. EC number 231-175-3.

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