Confined Spaces: HSE's Revised Workplace Exposure Limits

Workplace exposure limits (WELs) are the legal limits that have been set on the amount of dangerous substances that can be present in a workplace. In August 2018, the Health and Safety Executive updated its list of WELs and published a guide that includes the new limits for 31 substances.

Substances on the list include carbon monoxide, sulfur dioxide, and nitrogen dioxide – all of which can be present in confined spaces. They are classified as dangerous to the health of those working in confined spaces. This means that if substances are in a confined space they need to be tested, monitored, and controlled with the right tools.

Exposure – What Does It Mean?
"Exposure" or "being exposed" to a substance means it is present within someone's body.

Examples of this type of intake exposure include:

  • Swallowing
  • Skin contact
  • Injection
  • Breathing dust, gas, mist, or fumes

There can be thousands of harmful substances in confined spaces and environments – although only 500 of them are on the Workplace Exposure Limits. They are listed on the EH40 WELs file.

How to Check Workplace Exposure Levels
Knowing whether hazardous substances are below workplace exposure limits can only be done by monitoring a space. Exposure measurement requires a survey to assess employees' exposure to substances in the workplace environment. The survey should also aim to discover how and why this exposure happens, and what can be done to stop it or at least minimize the exposure amount.  

Personal sampling also can be performed – this entails taking an air sample close to the worker's breathing zone to measure the volumes of airborne elements present.

Points to consider when carrying out exposure measurement:

  • Exposures can vary from day to day
  • If results for a given task are below one third of the exposure limit, your controls are most probably good enough and don't require improvement
  • Measurement of exposure is not to replace controlling exposure. Exposure measurement is to be done after controlling measures have been put in place

Carrying out a COSHH Risk Assessment
A Control of Substances Hazardous to Health (COSHH) risk assessment focuses on identifying the hazards and risks in your workplace and implementing a system to improve the working environment.

Steps of a COSHH risk assessment generally involve:

1. Identifying the hazards. Identify substances that may be harmful to employees in the workspace.

2. Discover who might be harmed and how. There are a range of points to take into consideration when focusing on this part of the COSHH assessment. You'll need to think about how might workers be exposed to the harmful substances, how long people are being exposed for, and is anyone being exposed to the substances by accident? (This could include cleaners, maintenance workers, etc.)

3. Evaluating risks and implementing a prevention plan. Once a risk assessment has been carried out, deciding on which prevention route to go down is key. This ultimately depends on your workplace preferences, alongside complying with workplace health and safety laws.

Keeping Your Team Safe
When the reviewed workplace exposure limits are in place it will be more important than ever to have monitoring and risk prevention plans in place.

You can learn more about new workplace exposure limits by visiting the HSE website and by downloading the new EH40 booklet. In addition to monitoring exposure limits within your workplace to enforce safety importance, you can also widen your team’s knowledge of health and safety with a bespoke confined space training course.


Maddie Cartledge is a content marketing professional working on behalf of MRS Training & Rescue. She is experienced and knowledgeable when it comes to health and safety topics and training that can help prevent serious workplace incidents.

Posted on Oct 03, 2018


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