Agar (CAS 9002-18-0): storage and disposal

In a school or university microbiology prep room the powder usually sits near the culture media, and the first check is whether the tub is dry. It should be kept in a dry, labelled, well organised store with the lid screwed tight, dated on arrival and separate from food grade supplies. Powder left open takes up moisture and clumps. Unused ready-made plates are a different item, kept in a fridge with their lids on and a date, apart from any plates that have been used for culture. Pathology stores should keep the two groups physically separate so they cannot be confused.

Normal powder is loose and pale. What does not look right is a hard cake, a damp or sticky patch at the bottom of the tub, a yellowing or musty smell, and mould specks. Set plates age too: they dry out and shrink away from the edge, develop cloudy patches, or show colonies that nobody inoculated. Any plate showing growth should be treated as a biological question, not a chemical one. Record the condition of each item and whether any plate has been used or shows growth, and do not open a plate to check.

By specialist collection only. It never goes down the drain or into general waste. It is normally packed in a non-regulated or low hazard laboratory pack with compatible chemicals.

Before asking for a collection, record whether you hold powder, unused plates or used plates, because only the powder and any genuinely unused stock belong on this route. Used plates may be biological waste instead and are not chemical waste, so they should not be put into a chemical lab pack. On the sources we checked agar powder is not classified as hazardous, so it uses the non hazardous code 16 05 09, with 18 01 07 in a healthcare setting. A waste transfer note covers the move. Drains and general waste are not options for the powder.

Usually held as: powder, plates.

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.