Last reviewed 29 November 2012
Mike Sopp discusses the differing types of solvents found in laboratories and how they can be put to use and safely stored.
The safe storage of solvents is a key issue for laboratories and with many types of solvents being available for use, it is essential that the laboratory manager responsible for health and safety gives consideration and manages effectively the storage of solvents.
This will be based upon the principles of risk assessing and by following best practice in terms of the facilities chosen to store the solvents.
Solvents in laboratories
Solvents can be organic, meaning they contain carbon, or inorganic, meaning they do not contain carbon. There are many different types of solvents with contrasting physical and chemical properties. Water for example, is classed as an inorganic solvent. Organic solvents are classified by their chemical structure, of which there are three main types. These are:
hydrocarbon solvents: aliphatic and aromatic hydrocarbons
oxygenated solvents: alcohols, aldehydes, ketones, glycol ethers, esters and glycol ether esters
halogenated solvents: chlorinated and brominated hydrocarbons.
Solvents are typically used in laboratories to dissolve, suspend or extract other substances, generally without causing a change in the chemical nature of either the solvent or other substance being treated. They can also be used as a media for chemical reactions.
As with many of the materials found in laboratories, solvents are safe to use, transport and store provided best practice requirements are followed. The risks that arise from poor storage of solvents in laboratories include:
staff health and safety by solvents being stored in an inappropriate state or condition and/or an inappropriate place, without adequate warning of the hazards and potential for unwanted chemical reactions
fire and explosion from unwanted reactions, eg from incompatible solvents becoming mixed, which may result in generation of heat, fumes, gases and vapours
escalation of small incidents with the involvement of other materials incorrectly stored with solvents
escalation of incident and harm to persons as a result of emergency services being unable to ascertain the solvents involved, hence delaying mitigating actions.
For solvents, as with any substance stored in laboratories, the most effective way of determining appropriate storage requirements will be through the process of risk assessing.
As there can be many types of solvents, the risk assessment carried out could come under a number of pieces of legislation, not least, the:
Control of Substances Hazardous to Health Regulations 2002 (COSHH)
Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).
The starting point for any assessment for solvent use and storage will be the relevant Safety Data Sheet (SDS) for the solvent. In general terms, SDSs are required for a substance or mixture that is classified as dangerous under the Dangerous Substances Directive or Dangerous Preparations Directive, or classified as hazardous under the CLP Regulation (EC) No. 1272/2008.
Sub-heading 7 of the SDS will provide details for the safe handling and storage of the solvent. Clearly this will vary for each type of solvent but in general terms the following principles can be followed.
Minimise or restrict the quantities stored both in the main store/laboratory and avoiding over-ordering quantities.
Introduce an authorisation process for purchases and maintain records of location, keeper and quantities.
Obtain and keep centrally available hazard information on the solvents purchased and check existing information is up to date.
Utilise containers that are appropriate and well sealed or where necessary allow venting.
Use secondary containment to minimise the consequences of spillage, leakage or breakage.
In terms of the actual storage facilities, the general principles to follow are based upon segregation, separation and ventilation. The aims are to segregate incompatible solvents from each other; to separate hazardous solvents from unsuitable conditions for reasons of their toxicity, flammability or reactivity (by distance or physical means) and to provide adequate ventilation which will remove or dilute malodorous, noxious, toxic or flammable vapours and prevent their build-up.
The separation principle can be achieved through use of storage cupboards within the laboratory or through distance by having a separate storage facility from the laboratory. Clearly the design and materials of construction are important factors as is prevention of unauthorised access.
Other factors can be taken into consideration when storing solvents including prevention of over-storage so as to prevent breakages and spillages. Stock control with rotation of solvents and regular disposal of waste or unwanted/unused solvents will reduce the quantities stored and release valuable storage space.
System issues can be considered including the maintenance of an inventory that can be provided to the emergency services where required, use of suitable signage on storage facilities and the provision of information and instruction to staff on the appropriate use of storage facilities.
Fire and flammable solvents
Many solvents are flammable and classified as dangerous. In these circumstances, DSEAR require risks from indoor storage to be controlled by elimination or by reducing the quantities of substances to a minimum and by providing mitigation to protect against foreseeable incidents.
The Health and Safety Executive (HSE) highlights that it is the responsibility of the employer/dutyholder to justify the need to store any particular quantity of flammable liquid but the guiding principle is that “only the minimum quantity needed for frequently occurring activities or that required for use during 1/2 day or one shift should be present”.
The HSE also states that the maximum quantities that may be stored in cabinets and bins are no more than 50 litres for extremely, highly flammable liquids and those flammable liquids with a flashpoint below the maximum ambient temperature of the workroom/working area and no more than 250 litres for other flammable liquids with a higher flashpoint of up to 55°C.
When not in use, flammable solvents must be stored in suitable “cabinets or bins of fire-resisting construction and which are designed to retain spills (110% volume of the largest vessel normally stored in it)”. These should be located in designated areas, where possible away from the immediate processing area and not impeding means of escape.
Approved Code of Practice L136 details the performance requirements for fire resisting cupboards and bins, namely that:
the materials used to form the sides, top, bottom, door/s and lid are capable of providing the required fire resistance and reaction to fire
the joints between the sides, top and bottom of cupboards and bins are free from openings or gaps
the lid/doors are close fitting against the frame of the bin/cupboard, such that there is a nominal overlap between the frame and lid/doors in their closed position
the supports and fastenings should be of a material with a melting point greater than 750°C.
Many laboratories will use cabinets built to BS EN 14470-1:2004: Fire safety storage cabinets. Safety storage cabinets for flammable liquids, which may go beyond the minimum requirements of UK health and safety legislation.
The HSE notes that it is the responsibility of the employer/dutyholder to ensure that cabinets to any particular standard or design specification meet the minimum legal requirements but give a cautionary message in that “the use of cabinets with enhanced fire performance should not be seen as a substitute for the provision of dedicated store rooms and outdoor storage areas for the safe keeping of containers which are nominally empty or are not needed for current work”.
L136: Dangerous Substances and Explosive Atmospheres Regulations 2002. Approved Code of Practice and Guidance. Control and mitigation measures