Skip to content

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

Calcium carbide (CAS 75-20-7): storage and disposal

Calcium carbide survives in some school, college and university stores as grey lumps in an old tin, often legacy stock from demonstrations that are no longer run. It is classified as releasing flammable gas on contact with water, which can ignite spontaneously. That gas is acetylene, and an old tin may already hold some. Water, in any form, is what decides where it is kept and how it is handled.

CAS number
75-20-7
Form
Solid
Storage class
Flammable
Signal word
Danger
Usual EWC code
16 05 06*
  • Flammable pictogramFlammable

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

In a school prep room the tin is often found at the back of a high shelf, well behind years of newer stock. Check what is around it. It must be kept away from all water based stock, including ammonia solution, formalin, hydrochloric acid, hydrogen peroxide, sodium hydroxide and sodium hypochlorite, and away from taps, wet areas and any place that can flood. A flammable class cabinet with spill containment suits it, away from ignition sources, oxidisers and anything that might drip. Keep the lid on and the tin upright. A tin that has not been opened in years should stay shut and be reported for assessment, not inspected.

How to tell it has deteriorated

Intact lumps are hard and grey. Moisture that has got into a tin shows as a paler, powdery crust of lime on the lumps and around the rim, and lime dust from it is corrosive. Because the reaction with damp air releases acetylene, an old tin may be pressurised, so a bulging or domed lid is a serious sign. Rust through the tin, a lid that has seized and a label rubbed to nothing are all common on legacy stock. Do not open a tin to look. If a tin is domed, hissing, wet or heavily corroded, leave it where it is and get specialist advice.

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.

Never add water to calcium carbide, and never try to burn it, dissolve it or flush it away, as water releases flammable gas that can ignite. Leave the tin closed, upright and dry. It is hazardous waste and goes by specialist collection under 16 05 06*. Old tins are the awkward part of this one: the collection team needs to know how long the tin has been shut, whether the lid is domed or rusted, and whether lime crust or damp is visible. Say so plainly when you request a quote. It is packed away from water based stock, and an old tin may need extra care.

Waste codes and transport details for Calcium carbide
EWC code, laboratory chemicals16 05 06*
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.
  • Ammonia solutionReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Calcium hypochloriteOxidisers can ignite flammable materials or make a fire far more intense.
  • FormalinReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Hydrochloric acidReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Hydrogen peroxideReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Nitric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Potassium nitrateOxidisers can ignite flammable materials or make a fire far more intense.
Show 6 more
  • Potassium permanganateOxidisers can ignite flammable materials or make a fire far more intense.
  • Sodium hydroxideReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Sodium hypochloriteReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • 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: lumps, legacy stock.

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

  • H260 In contact with water releases flammable gases which may ignite spontaneously.

Substance as classified, dilutions may differ.

Questions

Can we open an old tin to see what is in it?

No. A tin that has been shut for years may hold acetylene under pressure, and any damp inside will have made more. Leave it closed, keep it dry and upright, and ask for specialist advice, describing what you can see from outside.

Where should calcium carbide be stored?

In a flammable class cabinet away from ignition sources and well away from water based stock such as ammonia solution, formalin, acids and hypochlorite. Keep it clear of taps and wet areas, with the lid tight and the tin upright.

What does damp calcium carbide look like?

Lumps that should be hard and grey become coated in a paler, powdery crust, and the same crust forms around the rim of the tin. Lime dust from it is corrosive. A bulging lid on an old tin means pressure, so leave it alone.

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

Hazard data source: GB mandatory classification list (HSE), retrieved 31 Oct 2026.

Request collection Add to register
Search the chemical database