How to dispose of old laboratory chemicals

Stage 1: Find the owner and stop the store growing

Before you touch a shelf, find out who is responsible. In a university, the waste may belong to a department and not the departed researcher. In a hospital, it may sit with the laboratory manager, with the trust's waste officer holding the contract. Get the name written down.

Then freeze the area. Tell colleagues nothing else should be added, because other people's unwanted bottles have a way of joining any pile marked for disposal. There is a legal reason too. Unauthorised additions can invalidate the description you will later sign.

Stage 2: Look first and do not move anything suspect

Walk the store with your hands in your pockets. You are looking for the small number of items that change the whole job. Stop and leave these in place:

• ethers and other peroxide formers that are undated, long opened or showing crystals around the cap
• picric acid, including stains and fixatives that contain it, if it looks dry or has crystals near the lid
• reactive metals where the oil has gone or a crust has formed
• bulging, corroded or leaking containers, and any bottle with a fused cap

Do not open, shake, wipe, test or carry any of these. Close the door, restrict access and get a specialist to assess them. If there is immediate danger, such as a fire risk, a smell that is making people ill or a leaking container you cannot get away from, leave and call 999. Tell them what you know about the store.

This is the one stage where our advice is absolute. A clear-out timetable never justifies handling a suspect container.

Stage 3: List every container in the safe part of the store

For everything else, write a line per container. Record the name, the CAS number if it is shown, the size, roughly how full it is, the location and its condition. Note anything unusual, such as old-style hazard labels that show the stock predates current labelling.

Two people work faster than one, with one reading and one writing. It is dull, and it pays for itself, as an accurate list is what allows a contractor to plan the packing, the vehicle and the paperwork. It also tells you what you actually hold. Expect much of the stock to be ordinary solvents, such as acetone and ethanol in partly used bottles, along with salts that have sat unopened for years.

Keep the list even after the work is finished. It becomes part of your record of what left the building.

Stage 4: Sort by hazard class on paper

Sort your list by hazard before you sort your shelves. Group flammables, oxidisers, acids, alkalis, toxic substances and anything else that needs to be kept apart. Moving sound bottles around is only needed where incompatible items sit together, and your own risk assessment should cover how that is done.

The list is also where you assign the waste codes. Your classification starts from the source of the waste. A hospital lab will usually use chapter 18, with 18 01 06* for hazardous chemicals. A university teaching or research lab will generally use 16 05 06* for laboratory chemicals containing hazardous substances. Where you are unsure, ask. Contractors do this routinely, though the duty to describe your waste correctly stays with you.

Look through the list for stock that could still be used. An in-date sealed bottle may be wanted by another group, and passing it on is better than destroying it. Keep this honest. A forty-year-old reagent is rarely a gift to anyone.

Stage 5: Hold it securely until collection

Waste awaiting collection is still your responsibility. Keep it in a locked store with limited access, apart from stock in use, clearly marked as waste and in its original containers. Flammables stay in their fire-resisting cabinet, as your DSEAR assessment still covers them, and the COSHH controls continue to apply until they leave.

Three things should not happen during this period. Do not decant into a single drum, as mixing hazardous waste with other waste is illegal. Do not pour anything down the sink to reduce the volume. Do not neutralise, dilute or otherwise treat anything to make it easier. Each of those creates a new unknown, and the last two may be offences in their own right.

Stage 6: Arrange a registered collection and keep the note

Hazardous waste can only leave with an authorised business, so check the carrier and the destination on the public register. Before collection, the consignment note needs a full description of each waste, its code, its weight in kilograms, its components and its hazard codes. Where small bottles are packed inside a larger container, the note must also describe the smaller containers.

Expect to see a chemist or trained packer sort the bottles by compatibility into lab packs on site. Make sure they have access, a clear route to the vehicle and someone who knows the store. In a teaching building, avoid changeover times. In a hospital, agree a route that keeps packed waste away from clinical areas.

In England, keep your copy of the note for three years at the premises that produced the waste. Keep the returns that follow with it.

Stopping it happening again

Many clear-outs share a root cause: stock that belonged to a person and not a system. Two changes make the biggest difference. Add a chemical handover to your leaver's checklist, so nobody leaves without signing off their shelves. And give every container a date when it arrives and when it is first opened.

If your store has labels missing or bottles you cannot date, our guidance on expired and unlabelled chemical disposal explains how that part of a job is handled.