Last reviewed 11 January 2016
Laboratories often contain a multitude of chemicals stored in a wide range of places, including cupboards, solvent bins, fridges, gas cylinder containment holds and barrels, but storage is about much more than just keeping benches clear. As Lisa Bushby explains, materials should be grouped according to their hazards and be separated.
The risks that arise from the poor storage of chemicals in laboratories include:
unwanted reactions — such as from incompatible chemicals becoming mixed — which may result in the generation of heat, fumes, gases or vapours that can give rise to a fire or explosion, cause physical damage, or pose a threat of toxic exposure
escalation of consequences, such as when a small incident that should be easy to control becomes far more serious because other material stored in the vicinity becomes involved
reluctance of emergency services to enter a building or laboratory to deal with an emergency situation, owing to uncertainty over what chemicals are in the laboratory and how safely they are stored
safety of staff — including other laboratory workers, cleaners or maintenance staff — being placed at risk because colleagues have stored chemicals in an inappropriate state or condition, or in an inappropriate place and without adequate warning of the hazards.
There are three key principles to safe chemical storage: separation, segregation and ventilation. Properly separating, storing and ventilating chemicals can be a highly effective way of minimising risk.
In order to separate, segregate and ensure adequate means of ventilation, materials should first be classified and grouped according to their hazards under the CLP Regulation. Laboratory managers need to be aware of any corrosive materials, flammable materials, explosives, oxidising or hazardous materials in their laboratories.
Hazardous chemicals should be separated from unsuitable conditions for reasons of their toxicity, flammability or reactivity. This can usually be achieved by means of storage cupboards which divide incompatible classes of hazardous chemicals.
The cupboards may need specific properties, such as ventilation or corrosive-resistant shelves, and will also need to provide secondary containment, such as spill trays or bunded shelves, and security.
Some chemicals will need specialist storage methods to separate them from incompatible conditions. Some may need to be stored under nitrogen, others at a controlled temperature, and many will require other specialist storage arrangements, including gas canisters.
Separation by distance is common practice in storage buildings, which may include dedicated flammable stores or gas cylinder compounds, but it can also be applied to chemicals in laboratories as a means of keeping incompatibles a safe distance apart. This practice could minimise the risk of more than one flammable cupboard becoming involved in a fire, for instance.
The key incompatibles to segregate from each other are strong acids from strong bases and strong oxidisers from organic or flammable materials. If mixing of these incompatible materials occurs due to spillage, breakage or leakage the reaction may generate heat, toxic vapours, fire or explosion.
Unsystematic storage on shelves should be avoided because it becomes difficult to find a particular item. An alphabetical arrangement is better, but it can lead to problems with incompatibles being stored next to each other. Storing chemicals together on open shelving may be acceptable for low-risk materials, however, certain specific classes of chemical must be segregated from each other. This may require them to be stored in different storage cupboards or, where this is not possible, in separate secondary containment and not stored above or close to each other.
For example, strong mineral acids (eg sulphuric, nitric, and hydrochloric) must be kept apart from strong bases. Even storage in the same cupboard on different shelves with spill trays is inadvisable. Hydrochloric acid in the same enclosure as an ammonia solution will cause a white deposit of ammonium chloride to form throughout the cupboard.
Highly flammable liquids (HFLs) should be kept away from other materials.
Chlorinated solvents, although they are generally non-flammable and even possible extinguishants, should not be stored together with HFLs as toxic vapours such as phosgene could be generated should a fire occur.
Some weak organic acids, such as acetic acid, may also be highly flammable or have a flash point just above 32°C, so should be segregated from other HFLs.
Volatile and odorous materials such as mercaptans should be kept to a minimum quantity in well-sealed containers that are stored in a secondary outer container within a ventilated cupboard.
For storage of corrosives, the materials must be compatible with and resistant to the corrosive nature of the stored material. Wooden shelves will not be suitable unless they are lined with a resistant material. Glass shelves for storing chemicals can also be corroded by certain materials and can be prone to shattering.
Any steel or aluminium components on corrosive storage cupboards stored out of doors must be treated to resist attack.
Certain groups of chemicals should be secured against unauthorised access. These include:
extremely toxic materials
other certain “high risk” materials depending on local procedures, such as carcinogens, teratogens, mutagens, or highly reactive materials
All approved flammable liquid storage shelves should have lipped/bunded shelves. Ensure that the shelves are not inserted upside down with their lips facing downwards, thus affording no spill protection.
Ventilation is often an essential requirement for the safe storage of hazardous chemicals. Its main function is to allow the dilution and extraction of vapours or gases that may escape from containers.
Ventilated cupboards are generally specially constructed and fitted beneath fume cupboards. Note, however, that excessive extract on such cupboards should be avoided as it will reduce the fume cupboard extract volume and affect its efficiency, possibly inducing unwanted draughts. It should also be noted that a fume cupboard itself is an enclosure primarily designed for undertaking work in and should not be used as means of providing ventilated storage unless dedicated to this purpose at the exclusion of other work.
Natural ventilation by vents or air bricks to the outside atmosphere is an alternative to mechanical ventilation in achieving the necessary air exchange and is often used in storerooms, especially those for flammable liquids. Vents should be of sufficient number and be at different heights (low to the ground and higher up) to vent both heavier and lighter than air vapours or gases and be in at least two walls, ideally those opposite each other, with an aim to achieve an air exchange rate of at least 5x an hour.
Maintaining an inventory of chemicals stored in any laboratory or on site is useful. Electronic chemical inventory management systems are available and allow chemicals to be checked in at delivery or upon receipt. When a centrally managed chemical store is available such systems can be used to record each use and location of chemicals and to allow for re-ordering when stocks are low. The inventory should also be accessible remotely so that in the event of an emergency services can be shown what is stored where.