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Safe storage of chemicals in the laboratory

Introduction

The typical biological research laboratory is home to a considerable range of chemicals requiring safe storage. Observations on a number of safety inspections within the department have revealed inappropriate storage of some chemicals within the laboratory. The following information intends to offer guidance on the basic principles of safe chemical storage and segregation in our laboratories, and possibly other areas within the Department of Biology where chemicals are used. However, the guidance is certainly not intended to be exhaustive, and users of chemicals are reminded of the importance of consulting other sources (e.g. specific Material Safety Data Sheets (MSDS)) for more specific and detailed information.

Types of specialised storage available

A number of facilities are used for the storage of these chemical substances, some of which are specially designed for the purpose. These include:

• Acid Cabinets
  These are made of acid resistant materials and contain a tray to contain any leakage or spillage
• Flammable Solvent Cabinets
  Fire resistant metal cabinets are typically used for the storage of flammable solvents. These offer fire resistance of at least 30 minutes as required by British Standard 476. A metal spill tray is used to contain spillages.
• Ventilated Cabinets
  These are cabinets fitted with forced ventilation and may be free-standing with their own extract system or positioned beneath a fume cupboard and attached to its duct.
  
  Ventilated cabinets are designed to safely store chemicals that give off noxious fumes and smells. These fumes are sucked away by forced ventilation. They should be used to store materials such as mercaptans and amines that have a strong smell. If you do not have a ventilated cabinet, containers of these noxious chemicals can be stored in sealed secondary containers that should only be opened in a fume cupboard.
  
  It should be noted that fume cupboards are not designed or intended for the storage of chemicals. The working surfaces of fume cupboards should therefore be kept clear of materials and containers when these are not needed for the ongoing work activities. Unnecessary storage of chemicals in fume cupboards disrupts the airflow resulting in a lower level of protection to users.

Some basic principles of chemical storage

• Store like materials with like. It is essential to segregate antagonistic substances to prevent dangerous interactions. All newly purchased chemicals should have a label on them identifying their hazard category (e.g. flammable, corrosive, oxidising, toxic etc.). A list of commonly used chemicals that should be segregated is listed below to assist storage.
• Store the minimum stock levels of hazardous chemicals in the laboratory
• Dispose of hazardous chemicals that are no longer required
• Store large breakable containers, particularly of liquids, below shoulder height
• Ensure containers and bottle tops are sealed properly to avoid unnecessary leakage of fumes / vapours
• Never carry a bottle of chemical by its top, and always carry Winchester bottles (2.5 litres) in carriers or baskets that are capable of providing proper support

Storage of different chemicals

1) Flammable Solvents - e.g. alcohols, toluene, hexane

The vapour above the liquid represents the main source of danger from flammable liquids. This vapour is very susceptible to ignition by naked flames, sparks from electric switches (e.g. thermostats) electric motors or from sparks produced electrostatically by friction. Precautions must therefore be taken to prevent contact between any of these and concentrated vapours of flammable liquids.

Flammable solvents should be stored in specialised metal flammable solvent containers, clearly labelled and positioned away from doors or other means of escape from the laboratory. It should be noted that no more than 50 litres of flammable material may be kept in any one laboratory room to reduce the risk of a serious laboratory fire. Reasonable quantities of flammable solvents may be kept in the open laboratory in suitable closed vessels of volume not exceeding 500 ml.

Flammable reagents and solvents must never be stored in a refrigerator unless they are spark proof. It is now Departmental policy that all laboratory fridges are spark proofed to avoid the possibility of an internal light or thermostat control unit providing a source of ignition for vapours produced from flammable substances.

Flammable solvents must never be stored with oxidising agents (e.g. hydrogen peroxide, nitric acid), reducing agents and concentrated acids (e.g. hydrochloric and sulphuric acids). A list of commonly used chemicals which should be segregated is listed below to assist storage. The MSDS should always be consulted if further information is required on storage and chemical incompatibilities of a particular chemical substance.

2) Chlorinated solvents - e.g. chloroform, trichlorethylene

Chlorinated solvents are best stored in ventilated cabinets separately from flammable solvents. This is because violent reactions can result from the mixing of certain flammable and chlorinated solvents. They should not be stored with alkali metals such as lithium, potassium or sodium, since any mixing can cause an explosion. They can be stored in metal bins if ventilated storage is not available.

3) Acids and alkalis

Acids and alkalis are often stored together as 'corrosives' in a metal cabinet with suitable metal spill tray to contain any spillage. Although acids and alkalis may be stored together, it is important to note that accidental mixing of concentrated materials will generate large quantities of heat and fumes.

Consideration must be given to the effects of acid fumes on any metal in the fittings and construction of the container. The use of ventilated cabinets are recommended where possible, allowing the removal of fumes at source. All containers / bottle tops must be suitably sealed to avoid unnecessary leakage of fumes.

4) Oxidisers - e.g. peroxides, perchlorates and nitrates

Oxidising substances should be stored in a metal cabinet and away from organic matter such as wood and paper. Oxidising agents must also never be stored with flammable solvents, since fires and explosions can result after any spillage, even without a naked flame or heat.

Perchloric acid is an extremely strong oxidising agent (especially in the concentrated form) which can react explosively with organic materials. It should ideally be stored separately on a metal tray of sand within a cabinet, away from organic materials or dehydrating agents such as sulphuric acid.

5) Poisons

Section 7 of the Poisons Act (1972) list toxic substances known as Schedule 1 Poisons. This has subsequently been amended over the years by several acts of Parliament. This list includes most of the well known poisons such as arsenic, cyanide, strychnine. They must be stored in a locked cupboard and a list kept of the contents. Any poison removed must be signed for. It is also good laboratory practice to store other dangerous substances labelled toxic / highly toxic (includes substances that are also carcinogenic / mutagenic / toxic to reproduction) in a locked cupboard, even though they do not appear in Schedule 1. Chemical suppliers should indicate whether a substance is a Schedule 1 poison at the time of purchase and will normally have a special order procedure for such materials.

6) Dangerous drugs and medicines

These should be stored in a locked cupboard. If it is necessary to store them at low temperatures the fridge or freezer used should be fitted with a lock.

Incompatible chemicals

A wide variety of chemicals react dangerously when mixed with certain other materials. Some examples of widely used incompatible chemicals are given below (substance in the left-hand column should not be mixed with substance(s) in right hand column!). These substances should be stored and handled so as to avoid accidental mixing. Please note that the absence of a chemical from the list does not mean that it is necessarily safe to mix it with any other chemical! You should always check with the MSDS if in doubt.