Safety Office

Section 9: Precautions with Chemicals

9.1 General Guidance

Work with chemicals can present toxicological and/or physical hazards. Where the work could present a toxicological, i.e. health, hazard then it is subject to the requirements of the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Work with substances presenting a flammable or explosion risk are subject to the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).

Substances defined as being hazardous to health include those that are very toxic, toxic, harmful, corrosive or irritant. These categories of danger are shown on the label of the container for the substance as commercially supplied. There are also a large number of chemicals for which there are occupational exposure limits. These are published in HSE Guidance Note EH40 which is up-dated annually and a copy held in the Safety Office. These chemicals are also subject to COSHH, as would be harmful intermediates or metabolites created during the reaction etc.

Substances with chronic or delayed effects, for example, carcinogenic, mutagenic, teratogenic or respiratory or skin sensitisation are also subject to these regulations. The manufacturers and suppliers have a legal duty to provide and maintain MSDS (Material Safety Data Sheets) information for the chemicals that they sell. Please refer to the suppliers web pages for safety information and data sheets:

Where substances hazardous to health are used the work needs to be assessed to identify whether there are any stages within it that could result in a harmful exposure. This requires consideration of the toxicity of the material, the quantity involved in relation to this, its physical form (power, in solution, gaseous etc.) and the route by which exposure can occur, i.e. inhalation, ingestion, absorption or via injection or cuts/grazes. Having identified those stages, if any, where a harmful exposure could occur, certain control measures need to be applied. A less or non-hazardous alternative should be used if possible. If not then exposure could be minimised, for example by working in a fume cupboard, using scrubbing devices, using the substance in a safer form (aqueous solution instead of powder) or containment within a sealed vessel. Good general ventilation of the working area is important. Personal protective equipment such as dust masks, gloves, impermeable clothing should only be used where engineering controls or procedural modifications are either not feasible or only partially effective. 

Under some circumstances health surveillance by the Occupational Health Unit will be needed. These circumstances are where an adverse health effect may occur as a result of the type of exposures occurring during the work and there is a means of detecting the effect. The main purpose is to identify any exposure-related ill health at an early a stage as possible. Safety Office Guidance details the University's arrangements for providing health surveillance for people whose work may involve a significant exposure to respiratory sensitisers. Some chemicals, metals and natural substances of animal or plant origin may give rise to sensitisation. Natural rubber latex PDF format(commonly used for some types of disposable surgical gloves) can also give rise to skin or respiratory sensitisation (see Section 8.4). Further information on Health Surveillance available can be obtained from Occupational Health.

For some work activities there may be standard procedures to ensure safe working with the chemical. On the other hand there could be situations where each chemical reaction or process requires a unique assessment which should be recorded permanently. In most cases this record should be written into the experimental notebook adjacent to the details of the process undertaken. The School or Departmental arrangements for your work area should be consulted as to which course of action is needed.

For the hazards associated with particular substances refer to the manufacturer’s hazards data sheets or consult a reference book. "Dangerous Properties of Industrial Materials" by N.I. Sax, "The Registry of Toxic Effects of Chemical Substances" by R.J. Lewis, "Hazards in the Chemical Laboratory" edited by S.G. Luxon (5th edition) and the Sigma-Aldrich "Library of Chemical Safety Data" are to be found in the George Green Library. Several Schools have computer database compilations of toxicity data and other reference texts. If it is possible to substitute a hazardous substance with a less hazardous one able to perform the same function, then this substitution must be made.

All users of chemicals must be adequately trained to be aware of the hazards of the materials they use and the correct precautions to be adopted. If necessary users should seek advice from specialists. For example the hazardous properties of many substances are not readily apparent, and there may be problems of incompatibility when two or more chemicals are mixed.

The use and storage of all chemicals should be adequately controlled, especially those which are flammable, explosive, toxic or carcinogenic. All containers must be labelled with accurate information as to the contents and where appropriate, with information on the hazards. The minimum quantity necessary should be used and hazardous materials should be safely disposed of as soon as possible after use. See Safety Office guidance on the safe storage of chemicals PDF formatand guidance on working with hazardous substances.

Before carrying out an experiment with an unfamiliar and potentially hazardous chemical, plans should be made to deal with any emergency arising from unexpected releases of materials by spillage or other means. For example, spill kits containing neutralising substances should be available and if appropriate suitable chemically resistant suits and overshoes. Where corrosive/toxic vapours could be released respiratory protective equipment and staff trained in its use should be made availableBreathing apparatus will only be appropriate where there is a rigorous regime of trained operators, maintenance and face fit testing is in place. 

When carrying out any chemical manipulation always have someone within easy calling distance who can render assistance or aid in case of accident. Potentially hazardous operations by lone workers are not allowed. 

Further information on chemical safety is available on the Safety Office website. There is also guidance on nano-materials.

9.2 Fume Cupboards

Fume cupboards provide one of the most important controls over exposure to hazardous substances. They can also provide protection against physical hazards. There should be clear indication of the purpose for which a fume cupboard may or may not be used. Users of fume cupboards must always match the work being undertaken to the suitability of the cupboard concerned. There must be a system for regularly monitoring the effective operation of fume cupboards.

Fume cupboards must provide effective containment of the fumes/vapours etc. This is achieved through selecting a suitable face velocity for the fumecupboard and the type of work and careful use of the cupboard.

    • Standard hazard work should be carried out in fumecupboards with a face velocity of 0.4 m/s.
    • Storage only is permitted in fumecupboards with a face velocity exceeding 0.2 m/s.
    • High hazard work might require an increased face velocity and/or a fumecupboard with an emission scrubbing system, usually a wet wash.

Poor housekeeping or layout of equipment in the fumecupboard can significantly reduce the effectiveness of containment. In particular ensure that:

    • The fume cupboard is working - check the airflow indicator and/or use an anemometer. A simple tell-tail (strip of paper to deflect with the air movement) can also be useful!
    • Do not overload the fume cupboard:
        • Leave a 150mm clear space at the front – "Safety Line".
        • Do not obstruct the air slots at the base of the back for the fume cupboard.
    • Always lower the sash when not working at it.
    • Don't leave or trail things over the sill – this can cause leakage out.

The Engineer's section of the Estate Office maintains a register of all fume cupboards and arranges for them to be examined and tested every 12-14 months. Copies of the result from this are held both by the School concerned and the Estate Office.

A considerable number and variety of chemical compounds should only ever be used inside an efficient fume cupboard; benzene and carbon tetrachloride are but two examples. You must always be aware of the hazardous properties of the compounds you are using so that risk of exposure can be estimated. If the hazards are unknown, then a fume cupboard should be used.

Further information is available from the fume cupboards page of this website.

9.3 Skin Hazards

Acids, alkalis and other corrosive materials can cause burns on the skin. Some chemicals have an irritating action and may cause sensitisation or dermatitis, while some others pass freely through the skin barrier and thereby directly into the blood stream. Toxic effects can be almost immediate, but frequently effects are delayed or may result from long-term exposure. Some chemicals are carcinogenic. It is prudent therefore to keep all chemicals off the skin.

Always wear the approved personal protection - i.e. safety glasses, laboratory coat and sensible stout shoes and keep bare legs covered. Rubber or plastic gloves should be worn when handling chemicals, and in cases where there is a risk of splashing then face shields, plastic aprons and rubber boots may be necessary.

You should be aware of the best method for dealing with accidental skin contact before using a chemical. In many cases the remedial action involves immediate and thorough washing and prolonged rinsing with water and, if in doubt, then this procedure should be used. However, many chemicals are not particularly soluble in water and alternative methods for removal are often necessary (e.g. soap and water may suffice). Unless you have information to the contrary, avoid the use of organic solvents for the washing process since some of them have the ability to carry contaminants through the skin.

9.4 Eye Hazards

It must be assumed that all chemicals will cause damage if allowed to contact the sensitive surface of the eye. Some chemicals have a severe damaging effect, especially acids, alkalis and those chemicals, which are classified as corrosive or as irritants. Many solvents fall into this category. Hence, the wearing of safety spectacles or other appropriate and approved eye protection in laboratories is essential when handling chemical compounds.

9.5 Pesticides

The Control of Pesticides Regulations (1986) require that any person who uses a pesticide shall take all reasonable precautions so as to protect the health of human beings, creatures and plants, and to safeguard the environment and in particular to avoid pollution of water. Trained personnel with a certificate of competence should use pesticides approved for agricultural purposes. Untrained personnel may only use pesticides under the direct supervision of such a person. Further guidance is given in a Code of Practice on the Agricultural and Horticultural use of Pesticides, which includes sections on operator training, storage and transport of pesticides, and the safe use of pesticides.

Local rules should outline appropriate systems of work which users must observe.

9.6 Risk of Poisoning - Planning for Emergencies

In all work involving the risk of poisoning it is particularly important that a comprehensive assessment is made under the COSHH Regulations before work starts. Very careful consideration must be given to the apparatus design and engineering controls so that the risk is minimised.

Particular chemical poisons may have a specific antidote. If there is one which may be administered by lay persons it should be made readily available beside the experiment.

If the treatment must be administered by medically trained personnel, make arrangements with the University Health Centre to have the recommended emergency treatment kit readily available for immediate use.

9.7 Personal Hygiene

All chemicals should be regarded as toxic by ingestion. Hence, pipetting liquids or solutions by mouth is strictly prohibited; use a pipette pump, syringe or a mechanical dispenser. Never deliberately taste, swallow or inhale any chemical.

Chemicals can also enter the body through the skin absorption or through the accidental inhalation of vapours or dusts. Suitable protective equipment must be worn when handling chemicals. Cuts and wounds are particularly vulnerable and may allow direct entry of chemical substances into the bloodstream. Broken skin should be covered with a suitable dressing, but if the wound is on the hand then the dressing should be waterproof and rubber gloves must be worn while handling chemicals.

Always wash your hands before touching other parts of your body (especially the area around the eyes) or before taking food.

Do not smoke, eat or drink in the presence of chemicals.

9.8 Flammable Liquids, Vapours or Gases

The majority of organic materials are flammable, and many organic solvents are highly flammable (e.g. alcohol, acetone, ether, petroleum products, and toluene—to name just a few). The quantity of any highly flammable liquid present in a work area must be as small as is reasonably practicable having regard to the processes or operations being carried out.

The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) define the controls for fire and explosion risks associated with working with flammable materials. They are concerned with fire and explosion risks from substances or preparations that may be hazardous due to the potential to give rise to fire, explosion or other similar event. The following classes of substances are covered:

    • Oxidising
    • Extremely flammable
    • Highly flammable
    • Flammable

These "Dangerous Substances" may give rise to fire or explosion in the form of gases, vapours, mists and dusts. The following controls are required:

    • Risk assessment
    • Elimination or reduction of risks
    • Identification and classification of areas where an explosive atmosphere may be produced (zoning of areas according to specified criteria for the potential for forming a hazardous atmosphere and selection of appropriate equipment that will not ignite it for use in the zones)
    • Preparation of accident, incident and emergency arrangements
    • Provision of information, instruction and training
    • Identification and marking of containers and pipes containing dangerous substances

This approach, i.e. the requirement for risk assessment is consistent with other recent health and safety legislation. Normal risk assessment procedures and documentation will satisfy these requirements.

Risk of fire or explosion

The risk assessment should consider how the substance could be released and the likelihood of it igniting under normal use, maintenance, and forseeable accident. The quantity, form and duration of the release are significant, for example whether a sufficient quantity or concentration to sustain a fire or explosion could be involved. Whether a release could be ignited will depend upon proximity to ignition sources such as standard, unprotected electrical equipment and switches that could produce a spark, naked flames, hot surfaces and sparks from grinding and cutting processes.

Control measures

Controls to prevent fire/explosion from occurring include correct design, selection and maintenance of the equipment and protective devices. Containers and pipework must be marked as to contents.

For flammable gas systems, installation in accordance with British Compressed Gases Association Codes of Practice would meet the physical requirements of these regulations - inert gases would not be covered by these regulations.

Those working with flammable liquids should also be aware of the existing guidelines within the following HSE documents:

Flammable liquids must be kept in securely lidded and labelled containers. When moved they should be carried in a manner to prevent breakage or spillage, for example enclosed Winchester carriers.

When decanting from drums, the drum and the receptacle must be earthed to prevent static build up – discharge of this is likely to ignite the liquid.

Solvents that need to be stored at low temperatures must be kept in purpose built spark-free refrigerators, not the usual domestic type. In the event of a solvent fire, water should not be used to fight it. Burning solvent usually floats on water and dousing with water can rapidly increase the spread of the fire!

Mixtures of flammable organic materials (whether gases, solvent vapours or dusts) and air may explode on ignition. To avoid this the proportion of flammable gas, vapour or dust in the air should be kept to a very low level by adopting safe working practices, giving careful thought to apparatus design, and by maintaining good ventilation, for example by working in a fumecupboard. The vicinity should be kept clear of ignition sources (e.g. flames, hot surfaces or sparks).


The regulations also specify criteria for the classification of hazardous zones on the basis of the frequency and duration that an explosive atmosphere of vapours, gases, mists or dusts may occur. Equipment for use in such zones must be selected on the basis of the requirements set out in the Equipment and Protective Systems Intended for use in Potentially Explosive Atmospheres regulations 1996, which correlate design specification with the zone of intended use.


Minor spillages must be cleaned up quickly. In the event of major spillages the laboratory should be ventilated by opening the windows, evacuated and the door closed. Do not switch any electrical equipment on or off since this could cause a flashback to the spillage.

Please note the following: 

    1. These Regulations repeal the Highly Flammable Liquids and Liquefied Petroleum Gases Regulations 1972, which previously required controls on storage and use of these types of flammable substances.
    2. The Petroleum Consolidation Act 1928 is amended to remove the requirement to licence certain types of solvent stores – licensing now only applies to storage of petroleum spirit in tanks for pumping to supply tanks of internal combustion engines.

9.9 Carcinogens, Mutagens and Substances Toxic to Reproduction

There are specific requirements under the COSHH Regulations concerning working with carcinogens.

Carcinogens are identifiable by the risk phrases R45 - "may cause cancer" or R49 - "may cause cancer by inhalation" and fall into three categories.

Carcinogens are divided into three categories:

    • Category 1 - substances known to be carcinogenic to humans. There is sufficient evidence to establish a causal association between human exposure to the substance and the development of cancer.
    • Category 2 - substances that should be regarded as if they are carcinogenic to humans, for which there is sufficient evidence, based on long-term animal studies and other relevant information, to provide a strong presumption that human exposure may result in the development of cancer.
    • Category 3 - substances that cause concern owing to possible carcinogenic effects but for which available information is not adequate to make satisfactory assessments.

Categories 1 and 2, if purchased from a supplier, will carry the "toxic" (T) symbol and the Risk Phrase R45 (may cause cancer) or R49 (may cause cancer by inhalation). These are subject to specific control under COSHH.

Category 3, if purchased from a supplier, carries the "harmful" (Xn) symbol and the Risk Phrase R40 (limited evidence of carcinogenic effect). These are not included in the COSHH definition of a carcinogen but are subject to the general requirements of COSHH.

Mutagens are substances that cause heritable genetic changes (mutations). Most mutations are harmful and most mutagens are carcinogens and vice versa. Substances that are known to impair fertility or to cause developmental toxicity in humans are defined as toxic to reproduction (STR). This definition covers a broader range of health effects than the earlier "teratogenic" which applied only to substances that adversely affected the developing foetus.

Mutagens and STRs are classified similarly to carcinogens in Categories 1 to 3:

    • Category 1 and 2 mutagens carry the Risk Phrase R46 "may cause heritable genetic damage". Substances toxic to reproduction carry the Phrase R60 "may impair fertility" or R61 "may cause harm to the unborn child".
    • Category 3 mutagens have the Risk Phrase "possible risk of irreversible effects" and Category 3 substances toxic to reproduction are classified by R62 "possible risk of impaired fertility" or R63 "possible risk of harm to the unborn child".

These substances, unlike carcinogens, are not specifically prescribed in COSSH. However because of the nature of the hazard, workers should adopt the precautions and principles outlined in this section.

As with any other chemical, a risk assessment must be carried out for the procedure involving the use of a carcinogen. The risk assessment must identify the means by which exposure can be prevented or, if not reasonably practicable, controlled.

Prevention of exposure can be achieved through substituting with a less harmful substance, modifying the process to avoid using the carcinogen, or avoiding the formation of carcinogenic by-products or intermediates. Where this is not reasonably practicable the first choice must be the use of a totally enclosed system such as a glove box or cytotoxic cabinet.

If prevention cannot be achieved then exposure should be controlled through the use of partial enclosure and/or local exhaust ventilation along with safe handling systems, the general principles of which include:

Handling must be confined to dedicated areas that are clearly identified with appropriate hazard signs and non-essential personnel excluded from these areas.

    • Minimise the quantity to be used and or frequency of exposure.
    • Try to avoid having to dispense powder by purchasing the carcinogen in pre-weighed vials/iso-vac containers.
    • If the compound is stable in solution then weigh out enough for several experiments and divide into suitable aliquots for future use.
    • Work in an enclosed glove box or if not available use a fume cupboard or powder weighing cabinet.
    • Always work over a tray.
    • If working in a fume cupboard be aware of air turbulence as this can spread fine powders within the fume cupboard.
    • If weighing fine powders be aware of static and try to reduce it by rinsing gloves first under water or using an earth strap.

Personal protective equipment may be used as secondary protection but must never be the primary means of controlling exposure.

    • Lab coat should be double fronted, side fastening with cuffs.
    • Gloves should be of the correct type depending on the nature of the compound and any associated solvent that may be involved. Check glove manufacturers charts or seek advice.
    • Respiratory protection (RPE) such as face masks may only be worn as a secondary means of protection in addition to working in a fume cupboard or in the event of a spill outside primary containment. RPE must be of the correct type and, depending on type, may require face fit testing.

Individuals required to work with carcinogens must be fully trained in how to handle carcinogens safely and be assessed as fully competent by their supervisor before handling the carcinogen. This training will be recorded.

A very high level of supervision should also be maintained to ensure that workplace standards and working practices are maintained.

Storage & Transport

Keep storage of carcinogenic substances to a minimum. Containers and storage areas must be clearly labelled with appropriate hazard signs and kept locked.

Transport in double containers that are clearly labelled as to hazard.

Further guidance on Carcinogens, Mutagens and Substances Toxic to Reproduction.

9.10 Nano-materials

Nano particles are usually defined as having one or more external dimensions in the order of 100 nm or less i.e.: < 0.1 micrometre/micron. A precautionary approach is advised when using nano-materials. In particular, there are concerns due to:

    • The small size of nano particles means that they could reach parts of biological systems that are not normally accessible by other larger particles. This process is known as translocation and in general, nanoparticles can translocate much more easily than other larger particles for example by:
        • The increased possibility of crossing cell boundaries,
        • Passing directly from the lungs into the blood stream and so on to all of the organs in the body.
        • Through deposition in the nose, directly to the brain.
        • Through skin absorption or penetration.
    • Due to their small size nanoparticles have a relatively much higher surface area than the same mass of larger particles. If surface area is a driver for toxicity this can result in potentially increased toxic effects.
    • If the rationale for developing nano-materials and nano particles is that they will have new and different properties than larger particles of the same material then it is conceivable that these new properties could include increased toxicity.

It must be noted that there are currently no Work Place Exposure Limits specifically for nano particles. The information contained within the Material Safety Data Sheet [MSDS] for a substance in conventional micron size, cannot be regarded as relevant for the same substance in the nano range.

For further information see Guidance and Safety Requirements for the Creation and Manipulation of Engineered Nano Materials.

9.11 Disposal of Waste Chemicals

Great care must be taken when disposing of potentially hazardous material. The appropriate waste disposal methods must be used as given in local waste disposal procedures.

Only innocuous materials may be disposed of via dustbins or drains. It may sometimes be possible to use a chemical deactivating process, as for example outlined in the Aldrich Chemical Company catalogue. Any such deactivation process must have undergone suitable and sufficient risk assessment to ensure that unnecessary risks are not introduced.

The disposal of hazardous substances is subject to a legal "Duty of Care" under the Environmental Protection Act 1990 and is also subject to the Hazardous Waste Regulations. Waste must be appropriately segregated, collected in suitable containers and correctly labelled as to contents.

The University has an Environmental Manager who works within the Estates Office who can provide advice and guidance on waste disposal procedures. The Environment section of the Estates Office web site contains more detailed information on the University’s arrangements for disposal of hazardous waste.

The University has approved a number of licensed waste contractors who must be used for the disposal of hazardous waste. These are listed on the Safety Office web site.

9.12 Restricted Chemicals

Certain classes of chemicals are subject to specific licensing controls due to the potential for misuse.

  1. Some chemicals that can be used for illicit manufacture of narcotic or psychotropic drugs (drug precursor substances) are subject to Home Office licensing. The licences are chargeable and are specific to the research area. The arrangements for working with these materials are summarised on the Safety Office website.
  2. Production, use or possession of chemicals that are agents associated with chemical warfare are subject to licensing controls under the Chemicals Weapons Act 1996 via the Department of Energy and Climate Change. Any quantity of, or intention of work with, a schedule 1 substance must be notified to the Safety Office for approval against any licence held or to be applied for. Approval is based on adequate risk assessment, written safe operating procedures and training records, and suitable facilities including security for the material and the disposal of waste. For Schedule 2 and 3 substances schools are required to provide an annual retrospective notification to the Safety Office via a local designated person. The Safety Office will submit the annual statutory declaration.
  3. Part 7 of the Anti-terrorism, Crime and Security Act 2001 places requirements on the security of pathogens and toxins in response to heightened concerns over potential terrorist threats. These regulations are overseen by the Home Office and enforced by the Police. The purpose of the regulations is to enable checks to be made on the physical security and access by individuals to specified more dangerous pathogens, toxins and related genetic material.

Premises holding stocks of any of the prescribed materials are required to be notified to the Home Office. The Safety Office submits such notifications on behalf of the University.

Further guidance on the security of pathogens and toxins.

9.13 Uranium and Thorium and their Compounds

These elements have non-radioactive uses but are subject to regulation and annual notification of holdings to regulatory authorities. There are also aggregate limits of holding for each site of the elemental and compound forms of these.

Local records of holdings must be maintained and notified to the Safety Office to enable annual statutory notifications to be made.

9.14 Respirable Crystalline Silica

For information on Respirable Crystalline Silica, please see Safety Office Information PDF format.


Safety Office

Pharmacy Building - Lower Ground Floor
University Park
University of Nottingham
Nottingham, NG7 2RD

Telephone: +44 (0)115 951 3401