Xylene: safe storage and disposal

Store stock xylene in a fire-resisting cabinet with other flammables, in its original closed container. Do not hold more on the open bench or in staining dishes than the process needs. Your DSEAR assessment should cover how much is kept out, the ignition sources nearby and how spills are dealt with.

Vapour is the working concern. Your COSHH assessment needs to address staining lines, coverslippers and tissue processors, where vapour can build up during a run or a reagent change. Keep staining dishes covered. Keep ducted extraction maintained, as an unserviced unit gives false reassurance.

Plan a waste location too. Spent xylene is a flammable liquid in its own right, and the waste container needs the same respect as the stock bottle. Keep it closed, inside a suitable bund or cabinet and clearly marked, and not by the door or on the floor of the staining room.

Stock xylene is stable when sealed and shows little sign of age. Look instead at the container and the seal, with a dropping level pointing to a poor closure. Old plastic containers may soften, and metal caps can corrode.

Used xylene is another matter. It picks up wax, water from poorly dehydrated tissue, stain carry-over and, in some labs, a little alcohol. You may see cloudiness, a milky look, a yellow or stained tint or solid wax at the bottom in cold weather. In a staining line, cloudiness often indicates water carry-over. Those signs tell you the solvent is spent, and what you see should go in the description of the waste.

Xylene goes by specialist collection. Do not put it down the sink, including small volumes from a staining dish, and do not leave it to evaporate.

The solvents entry 20 01 13* belongs to municipal collections and is not the normal code for a laboratory collection. For transport, xylene is UN 1307, packing group III.

The classification rules start with the source of the waste, which is why a hospital histology lab uses chapter 18 first. Separately collected waste solvents can fall under chapter 14, such as 14 06 03*, depending on their source. A full waste description is required on a consignment note, so "spent xylene from tissue processing, containing paraffin wax and stain residue" is the right kind of wording. The note also asks for a weight in kilograms, and a reliable conversion factor from litres is worth having for your regular containers.

Regular streams like this suit scheduled solvent waste collection. That keeps spent solvent from building up beyond what your fire assessment allows.

Histology departments can produce regular containers of spent solvent from processors and stainers, alongside reagent bottles and contaminated wipes. Xylene stock in schools is usually small, often in part-used bottles, and it has sometimes been unused for years.

Usually held as: mixed isomers, clearing agent.

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.