Dry ice (CAS 124-38-9): storage and disposal

Pressure from a sealed container is what decides where dry ice goes. As the solid turns to gas it needs somewhere to escape, so it must never go in a screw top bottle, a sealed tub or a tightly taped box, however convenient that looks in a busy lab. An insulated box with a loose lid, in a well ventilated room, is the usual holding place. Closed spaces are a separate concern. Carbon dioxide build-up in a closed room or a fridge is an asphyxiation risk, so do not leave it in a walk in cold room, a small store or a domestic style fridge. A sample shipment that arrives with it should be unpacked in an open area and not left overnight in a small office.

Start with the box. A delivery carton should be intact, with a loose or vented lid and a label that says what it is. Tape over a vent, a domed lid or a bulging plastic tub are all warning signs of pressure, and anyone seeing one should keep clear and ask for advice. Unlike a stored chemical, dry ice does not go off. The pellets or block simply shrink as they turn to gas, which is what you should expect, and frost on the outer surface of the box is normal. There are few other visual signs. A box found empty with nobody knowing why it was there usually tells you the contents have gone, not that anything is wrong.

This does not go through our standard collection route. It is arranged by manual enquiry, and never goes down the drain or into general waste.

It does not leave through an ordinary chemical collection, as it is not a normal chemical collection item, and it is not quoted online. Please ask before arranging anything. Send a manual enquiry stating the amount, the form, how it is being held and why it remains on site. A store assessment is recommended where it is a regular feature of work, for instance in a pathology department that often receives it. It is not classified as hazardous on the sources we checked, but it still needs an accurate description. Never seal it into a waste container, and do not put it in a sink, a drain, a general waste bin or a skip. Do not try to treat it while you wait for an answer.

Usually held as: pellets, block.

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.