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

d-Limonene (CAS 5989-27-5): storage and disposal

d-Limonene is the citrus-smelling liquid used as a clearing agent in histology and as a dental solvent, and it also appears in college and university stores. It is a flammable liquid, may be fatal if swallowed and enters the airways, irritates skin, can cause an allergic skin reaction and is very toxic to aquatic life. Its pleasant smell is the thing most likely to lead people to treat it lightly.

CAS number
5989-27-5
Form
Liquid
Storage class
Flammable
Signal word
Danger
Usual EWC code
16 05 06*
  • Flammable pictogramFlammable
  • Harmful or irritant pictogramHarmful or irritant
  • Serious health hazard pictogramSerious health hazard
  • 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

Oxidisers are what limonene must be kept apart from, because they can ignite a flammable liquid and make any fire far more intense, and oxidising acids and corrosive leaks present the same danger. Keep it in the ventilated flammables cabinet, on a tray, away from heat. Because it can cause an allergic skin reaction, store it low so staff are not reaching over it, and keep it away from food areas, since the orange smell has led to confusion with cleaning products in shared rooms. Dental surgeries should keep the small bottles inside the closed cupboard rather than on the bench.

How to tell it has deteriorated

On the shelf, the first sign is usually a change in the liquid itself. Old limonene darkens from pale to yellow, thickens slightly and loses the fresh citrus smell for something sharper and staler, as it reacts with air over time. Treat sticky residue round the cap with care, since the skin allergy hazard applies to the liquid and to the dried deposit. Also check for a lowered level, a cracked or perished cap and a label that has lost its writing. A bottle of limonene relabelled as orange oil or citrus solvent should be listed under both names.

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.

A lab pack grouped with compatible flammable organics is how limonene is collected, packed by the collector in UN approved packaging. It must not be poured into a sink or drain because it is very toxic to aquatic life, and it must not be put in a bin because of the allergy hazard. Histology and dental users should say whether it is clean or used clearing agent with wax and tissue. Teaching labs usually fit 16 05 06*, a loose discarded organic chemical uses 16 05 08*, and human healthcare settings can use 18 01 06*.

Waste codes and transport details for d-Limonene
EWC code, laboratory chemicals16 05 06*
Discarded organic chemical, not a laboratory pack16 05 08*
Human healthcare setting18 01 06*
Hazardous wasteYes

20 01 13* (solvents) belongs to municipal collections and is shown for reference only. It is not the normal code for a laboratory collection.

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.
  • Calcium hypochloriteOxidisers can ignite flammable materials or make a fire far more intense.
  • Hydrochloric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Hydrogen peroxideOxidisers can ignite flammable materials or make a fire far more intense.
  • 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.
  • Potassium permanganateOxidisers can ignite flammable materials or make a fire far more intense.
  • Sulfuric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
Show 2 more
  • 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: clearing agent, dental solvent.

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

  • H226 Flammable liquid and vapour.
  • H304 May be fatal if swallowed and enters airways.
  • H315 Causes skin irritation.
  • H317 May cause an allergic skin reaction.
  • H400 Very toxic to aquatic life.
  • H412 Harmful to aquatic life with long lasting effects.
Precautionary statements
  • P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
  • P233 Keep container tightly closed.
  • P240 Ground and bond container and receiving equipment.
  • P241 Use explosion-proof electrical, ventilating and lighting equipment.
  • P242 Use non-sparking tools.
  • P243 Take action to prevent static discharges.
  • P261 Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P272 Contaminated work clothing should not be allowed out of the workplace.
  • P273 Avoid release to the environment.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P301+P316 IF SWALLOWED: Get emergency medical help immediately.
  • P302+P352 IF ON SKIN: Wash with plenty of water.
  • P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or shower.
  • P321 Specific treatment (see supplemental first aid instruction on this label).
  • P331 Do NOT induce vomiting.
  • P332+P317 If skin irritation occurs: Get medical help.
  • P333+P317 If skin irritation or rash occurs: Get medical help.
  • P362+P364 Take off contaminated clothing. And wash it before reuse.
  • P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
  • P391 Collect spillage.
  • P403+P235 Store in a well-ventilated place. Keep cool.
  • P405 Store locked up.
  • P501 Dispose of contents and container in accordance with local, regional, national and international regulations.

Substance as classified, dilutions may differ.

Questions

Does old limonene go off?

Yes, it darkens, thickens slightly and the citrus smell turns sharper as it reacts with air. It remains a flammable liquid with an allergy hazard, so keep it capped, labelled and in the flammables cabinet until collection.

Is limonene a safe replacement for xylene in histology?

It is a different substance with its own classification: flammable, a skin allergen and very toxic to aquatic life. Treat it with the same care as any solvent in your risk assessment. Whether it suits a protocol is a decision for your lab.

Can dental surgeries put used limonene in clinical waste?

No. It is classified as a hazardous chemical, so it is not clinical waste. Keep it in a labelled closed bottle and list it for specialist collection, noting it as used solvent if it has been in contact with materials.

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 C10H16. EC number 227-813-5.

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