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      • Published 17 Jan 2023
      • Last Modified 15 Aug 2023
    • 15 min

    A Practical Guide to COSHH Safety

    Awareness of issues surrounding Control of Substances Hazardous to Health (COSHH) is necessary in every workplace. This guide covers the necessary steps employers should take to ensure a legal and responsible approach is taken to meet regulations.

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    Introduction to COSHH Safety

    What is COSHH?

    COSHH is an acronym standing for Control of Substances Hazardous to Health.

    It's an important branch of health and safety legislation, and like most official H&S protocols it's built around a clearly defined legal framework – namely the Control of Substances Hazardous to Health Regulations 2002 (updated in 2004).

    The law states that employers are required to prevent, reduce or (at the very least, where total prevention or significant reduction are unfeasible) control their workers' exposure to hazardous substances for the protection of their health.

    Awareness of issues around COSHH is a key part of any coherent health and safety approach, whether in the workplace or at home.

    Awareness of General Hazard Types

    Running almost any type of workplace today will typically involve some form of substance that, if used incorrectly or without the proper precautions in place, is potentially hazardous to the health of staff and/or the public.

    Hazardous substances and materials may be present in many different physical forms. Manufacturing paints and sprays, biological waste, chemical disinfectants in cleaning or treatment environments, printing solvents, silica or metal residues from heavy industry, machined sawdust, and even bakery flour are all common examples of substances that fall under COSHH regulation.

    The full list includes:

    • Chemicals and chemical-containing products
    • Substances liable to cause harm on direct skin contact
    • Nanoparticles
    • Fumes (metal, rubber, solder)
    • Gases, including asphyxiating gases (e.g. chlorine, carbon monoxide)
    • Vapours and mists (particularly of solvents, isocyanates, and irritants such as acids)
    • Dusts and powders (wood, cement, silica, flour)
    • Germs and other biological agents
    • Fibres (such as glass or ceramic fibre)

    Exposure to any of the sorts of substances listed above can be harmful in a variety of ways, depending on the uptake method (the route a harmful substance takes into the body). The main potential uptake methods are inhalation, skin contact, injection and ingestion (swallowing).

    Basic Safety Approaches

    The crux of any sensible, legal and responsible approach to COSHH safety will always involve the following key steps:

    • Understanding COSHH regulations
    • Assessing exposure
    • Controlling exposure
    • Monitoring and reviewing protocols
    • Educating workers
    • Planning for emergencies

    The rest of this guide will cover each of the above steps in more detail.

    Understanding COSHH Regulations

    The COSHH Regulations 2002 introduce a number of separate rules and guidelines that apply to all workplaces in addition to the existing General Health and Safety Legislation.

    Breach of these regulations by an employer is a crime, punishable by an unlimited fine. Conviction can apply either to individuals or to entire corporations.

    Substances directly identified as COSHH concerns in the regulations include all materials classed as toxic, very toxic, corrosive, harmful or irritant. In addition, biological agents and dust in substantial concentrations are also covered by the regulations.

    Eight Core Principles

    The Regulations are based on eight core principles, which apply to all employers regardless of whether a particular substance being used has a Workplace Exposure Limit (WEL).

    The key principles and obligations for employers are broadly defined as follows:

    1. Assess the risks to health of hazardous substances used in or created by all workplace activities
    2. Decide what precautions are needed, and do not carry out work that could expose staff to hazardous substances without ensuring full COSHH compliance is in place
    3. Prevent or adequately control exposure employee exposure
    4. Ensure control measures are used and maintained 24/7 and at all stages of production
    5. Monitor exposure levels and continually amend processes, safety guidelines and responses as necessary
    6. Carry out appropriate health surveillance in response to risk assessment or specific COSHH requirements
    7. Prepare plans and procedures in case of an accident or incident, including a suitable and well-drilled emergency response protocol
    8. Ensure all employees are properly educated, trained and informed, providing them with all the latest information on new products, systems and potential risks

    Workplace Exposure Limits (WELs)

    As part of the updated COSHH Regulations, a new system of Workplace Exposure Limits (WELs) has now replaced the former Maximum Exposure Limits (MELs) and Occupational Exposure Standards (OESs).

    Regulation 7 of the COSHH framework states that an employer's control of exposure may only be deemed adequate if the Workplace Exposure Limit (WEL) for any given substance is not exceeded.

    The WEL value of a potentially hazardous substance is expressed as a time-weighted average (TWA), and there are two variations:

    • Long-term Exposure Limit (LTEL) – the maximum level of exposure permitted in an 8-hour period. LTEL limits are designed to reduce the risk of harm from cumulative exposure, where chronic ill-health conditions arise from the daily uptake of hazardous substances in smaller doses
    • Short-term exposure limit (STEL) – the maximum level of exposure permitted in a 15-minute period. STEL limits typically relate to 'peak exposure' incidents and are designed to protect against any acute ill-health effects caused by sudden and more direct exposure to higher concentrations of hazardous substances

    Important: not all chemicals used in the workplace have defined WEL values, but this doesn't mean they're not hazardous.

    The sheer number and diversity of products being used in workplaces today make it impossible for a truly definitive, up-to-the-minute list to exist at all times, but new substances are frequently added and revised in regular edits and supplements to the HSE's core EH40 Workplace Exposure Limits handbook (see resources section).

    Although COSHH Regulations are complementary to the CLP Regulation on chemical labelling, it's also important to remember that not all potentially harmful substances will necessarily carry a hazard warning label. Many substances that are technically classed as non-hazardous can quickly become COSHH concerns if used incorrectly or without due care.

    Assessing, Controlling and Monitoring COSHH Safety at Work


    COSHH regulations impose duties on employers to demonstrate due care and attention regarding employee health, by ensuring that suitable and sufficient COSHH risk assessments are undertaken.

    Any workplace with five or more employees must record its COSHH risk assessment. However, all workplaces are advised to do so regardless of staff numbers, in case of need for future reference and to help with ongoing safety improvement plans.

    It's important to note that a proper risk assessment is far more than just an 'on paper' exercise.

    Depending on the environment, it will commonly involve specific activities such as scientific monitoring of air quality for the presence of hazardous substances (used or generated, including dust and particulates), ensuring levels remain within any stated WEL values.

    Like any health and safety assessment, a COSHH assessment should begin with a thorough walk-around observation of all areas and processes in the workplace, including waste storage and disposal systems.

    In doing so, be aware of the difference between a 'hazard' and a 'risk' – a hazard is a source of potential harm, whereas the risk is the likelihood of that harm occurring.

    In conducting a comprehensive risk assessment, employers should take all of the following steps. The aim is to identify any situations, products or activities (directed or otherwise) that may cause harm:

    • Walking around the workplace and observing processes and behaviours
    • Examining accident, incident and near-miss records, even under previous ownership where applicable
    • Listing all substances and products used or generated in the workplace, and gathering as much information as possible on each substance and the risks associated with them
    • Looking at the information on labels, in suppliers' catalogues, and on material safety data sheets
    • Contacting the substance supplier
    • Speaking to an independent consultant
    • Gathering feedback and perspective from employees (include both experienced and newer staff wherever possible)

    Once potential hazards have been identified, the next stage involves building an understanding of how harm may come about, and precisely who is at risk in each case:

    • What are the potential uptake methods (spills, swallowing, breathing, injection) at each site?
    • What would the effects of different types of exposures be?
    • Who else might come into contact with a particular hazardous substance, besides the employee handling it directly? (Consider cleaners, maintenance workers and non-employees at risk through secondary exposure)
    • How often, and for how long, are different employees exposed to varying levels of hazardous substances?
    • What actions can lead to greater levels of exposure for some people than others? (Certain substances can pose a relatively minimal risk during transport or direct handling, for example, but a much higher risk during heating, mixing, cleaning or disposal)


    Controlling exposure and risk through COSHH is about putting your risk assessment observations into a coherent plan of action.

    This in itself is a three-stage process:

    1. Deciding on necessary precautions
    2. Preventing or limiting exposure
    3. Ensuring safety measures are used and maintained

    In working out which precautions will be necessary, it's useful to consider 'What?, Where?, Who?, When?, and Why?':

    • What processes are being undertaken, and what hazardous substances are being used, generated and recorded on safety sheets?
    • Where are these activities taking place, and how might the immediate workplace environment be reducing or exacerbating risk to staff and other people?
    • Who is carrying out specific actions? Are they fully trained to do so, and do they understand the risks?
    • When are exposure-related activities taking place – how often, and for how long? Are there regular peak exposure times that might require additional measures?
    • Why are potential exposure levels higher than they could be, and is there a practical way to make changes to reduce them?

    Once you've identified which precautions will be important to take, it's time to move on to implementing these controls to reduce exposure levels. This can be done in various ways, listed here in order of most to least preferable/effective:

    1. Eliminating the source of the risk/hazard
      1. The ideal solution when dealing with COSHH issues is to remove the source of the hazard entirely
      2. In many cases, this will be impossible, as the substance or practice concerned will be central to the job at hand
      3. However, it's always worth questioning whether a specific product or process is absolutely essential to arriving at the end goal
    2. Substituting hazardous substances to lower risk levels
      1. Where elimination isn't practical, substitution might be the next best option
      2. Are there different substances or systems that can be used to achieve similar effects at lower exposure risk?
      3. Be aware that any substitutions made can potentially introduce new hazards, and should also form part of a risk assessment update
    3. Improving infrastructure, processes or systems
      1. If a workplace can't feasibly eliminate or substitute hazardous substances, changing and improving the ways they're physically handled or used should be the aim of any control measures
      2. Engineering-based updates to working practices might involve looking at such areas as modification of machinery, automation of certain processes, better isolation of hazardous materials and tasks, or improvements to the physical environment (e.g. improving ventilation or disposal systems)
    4. Administrative changes for better hazard management can often help reduce risk among staff. This might include such measures as:
      1. Working out improved shift patterns to achieve lower exposure times or more continual supervision
      2. Publishing risk-related rules and guidelines more visibly to achieve greater general awareness
      3. Greater provision of frequent training sessions and courses to help employees retain up-to-date knowledge and skills
    5. Personal Protective Equipment (PPE) supply and monitoring . Although equipping staff with all necessary clothing and tools for physical protection is a legal requirement in most workplaces, it's important for employers to remember that this is always a last line of defence:
      1. It is not a substitute for optimal practice and procedure elsewhere and does not transfer full responsibility for safety management to the wearer
      2. Supply of PPE can also be significantly more expensive in the long run than other engineered or administrative safety measures, as items will need to be repaired and replaced on a regular basis
      3. Any PPE supplied must be suitable for both the task and the wearer to be effective, and always paired with ongoing education and monitoring regarding its proper use

    Monitoring and Reviewing

    After the risk assessment has been done, measures to control exposure levels have been identified, and practical steps to improve COSHH have been taken, it's important to maintain a system of regular checks and balances to ensure that safety management continues to be effective.

    A key element in this is keeping risk assessment and safety knowledge up to date.

    New products or systems are continually introduced into manufacturing processes that, while often lowering a specific area of risk, can frequently introduce new potential hazards of their own.

    Good times to update or re-run an assessment include:

    • Annually, as part of a regular schedule
    • Whenever changes are made to the design or suppliers of tools and machinery
    • Whenever a new substance or chemical is introduced
    • Whenever an existing substance is modified, updated, or new information on it becomes available
    • Before and after changes to processes or workflow
    • During relocation to new premises, or physical alterations to a work area or environment
    • As newer staff are hired, or responsibilities transferred
    • Before starting a new project or product line

    Another hugely important stage in the ongoing monitoring process is giving and receiving feedback on worker behaviour regarding COSHH practices.

    It can prove difficult to encourage workers to abide by best practice guidelines, particularly when introducing more experienced staff to new protocols. To combat this, it's crucial to make employees feel more invested in defining and upholding safety measures. This can be helped by:

    • Directly involving them, through regular consultation, in the design of machinery, products and safety systems wherever possible
    • Publishing and displaying rules and guidelines very visibly, and providing regular training updates
    • Ensuring there is always adequate supervision available in the immediate environment
    • Strict logging and archiving of all records regarding equipment use, maintenance or replacement, employee requests or concerns, and full incident reports
    • Frequently reviewing procedures and protocols – again, with direct employer input – to ensure checks and supervision systems don't feel excessive or outdated

    Health Surveillance

    Health surveillance is a system of ongoing health checks for employees that can be extremely important in certain types of workplaces.

    Some types of regular health checks are required by law for employees who are unavoidably exposed to substances or environments hazardous to health.

    Health surveillance is important for:

    • Detecting ill-health effects at an early stage
    • Providing data to help employers evaluate risk
    • Enabling employees to raise concerns about health at work
    • Highlighting lapses in control measures for improved risk assessment
    • Providing an opportunity to back up staff training and education programmes

    Important notes on health surveillance:

    • It is not a substitute for a comprehensive risk assessment
    • It should be specifically targeted, not used in a 'blanket coverage' approach - this is costly and can yield misleading results
    • As a legal requirement, it should not be confused with general health-monitoring activities in cases where work-related health effects are suspected but unestablished
    • It should not be confused with general workplace well-being programmes and initiatives (exercise, mindfulness, diet etc)
    • It is unrelated to other legal obligations in line with specific 'fitness to work' requirements, including relevant tests for drivers and machine operators

    Training and Educating Workers

    Full, certified training should be given to all workforces involved in procedures that could potentially result in exposure to harmful substances, either directly or through proximity/secondary contact.

    The core aims of training sessions and courses should be to give all employees:

    • An understanding of which workplace substances be hazardous to health, and how
    • Up-to-date knowledge and clear definitions of exposure limits
    • The skills to understand exposure issues, and to conduct COSHH risk assessments for their own individual areas and tasks
    • A greater understanding of practical control measures and safer methods of working

    It's also vital to provide full training on the importance, correct use and maintenance of any PPE equipment supplied, including respirators, protective gloves, eyewear, and all clothing. Be sure to include guidance on:

    • What constitutes an effective and comfortable fit
    • How to spot and report issues or problems with PPE
    • Whether it requires any regular user maintenance or cleaning
    • Whether it potentially introduces any new hazards of its own

    Emergency Planning

    Emergency planning should be carried out as part of an overall risk assessment strategy. The key elements of a good emergency plan are:

    • Identification of different potential emergency types (e.g. explosion, flooding, leaks and spills), and devising of a suitable response process for each case
    • Publication of clear, visible, and universally understood procedures to be followed in the event of an emergency – including the nomination of competent persons and assignment of specific responsibilities, instructions on raising an alarm, location and use exits or escape routes, location of assembly points, a protocol for contacting emergency services, and evacuation of disabled persons
    • Assigning specific responsibilities to competent persons, all of whom have formally agreed and are aware of their role, and have been fully trained to perform it using the most recent systems and equipment in place
    • Keeping accurate, up-to-date, accessible maintenance and instruction logs for all alarms, backup systems and other emergency equipment
    • Outlining of any potential risks posed to non-employees (e.g. other building users, nearby businesses or members of the public), and identification of measures to mitigate these risks
    • Regular scheduling of training updates and drill sessions