EH40 Workplace Exposure Limits: Everything Employers Must Know in 2026
If you run a business where workers handle chemicals, dust, fumes, or gases, you need to know about EH40. It is not just a technical document, it is the rulebook that protects your workers and keeps your business on the right side of the law.
This guide breaks it all down in plain language.
What Is EH40?
EH40 is a document published by the Health and Safety Executive (HSE). It lists the maximum amount of hazardous substances workers can safely breathe in during their working day. These limits are called Workplace Exposure Limits, or WELs. Think of WELs as legal speed limits for airborne hazards. Just as you must not drive above the speed limit, you must not allow workers to be exposed above these levels.
EH40 covers substances like:
- Chemical vapours and solvents
- Dust from wood, silica, and grain
- Welding fumes and metal particles
- Gases such as carbon monoxide and hydrogen sulphide
If your workplace produces or uses any of these, EH40 applies to you.
The Two Types of Exposure Limits
EH40 uses two key measurements to set limits:
- The 8-Hour Time Weighted Average (TWA) This is the average exposure over a full working day. It protects workers from long-term health damage caused by breathing in harmful substances day after day, year after year.
- The Short-Term Exposure Limit (STEL) This is the maximum exposure allowed over any 15-minute period. Some substances can cause immediate harm, irritation, dizziness, or worse, even from a brief burst of exposure. The STEL exists to prevent that.
Both limits can apply to the same substance at the same time. Staying within one does not automatically mean you are within the other.
Why This Matters for Employers in 2026
The stakes have never been higher. The HSE has been tightening limits, increasing inspections, and pursuing more prosecutions. Here is what you risk if you ignore EH40:
- Criminal prosecution with unlimited fines and up to two years in prison
- Prohibition notices that shut down your operation immediately
- Civil compensation claims from workers who develop occupational diseases
- Reputational damage that affects clients, insurers, and recruitment
Beyond legal risk, there is a human cost. Occupational diseases, including lung disease, occupational asthma, and cancer, are largely preventable. EH40 exists because workers deserve to go home healthy.
What Are Your Legal Duties?
EH40 works alongside the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Together, they create a clear set of employer obligations:
Assess the risks. You must identify every hazardous substance in your workplace, understand who is exposed, and evaluate how serious that exposure is. This assessment must be written down and kept up to date.
Monitor exposure levels. You need to measure the actual concentration of harmful substances in the air your workers breathe. Personal air sampling, where a small device is worn by the worker throughout their shift, is the most accurate method.
Put controls in place. If exposure is a risk, you must act. Controls should follow the hierarchy from most to least effective: eliminate the substance, substitute it with something safer, use engineering controls like ventilation, apply administrative changes, and finally use personal protective equipment (PPE).
Train your workers. Every employee who works with hazardous substances must understand what they are handling, what the risks are, and how the controls protect them.
Keep records. Monitoring results, risk assessments, and training records must all be documented and retained. Monitoring records must be kept for at least five years, or 40 years for substances with long-term biological effects.
The Right Way to Control Exposure
Many employers make the mistake of going straight to PPE, handing out masks and assuming the job is done. That is not good enough.
The correct approach follows a strict priority order:
- Eliminate the hazardous substance entirely if possible
- Substitute it with a less dangerous alternatives
- Engineering controls like local exhaust ventilation, enclosures, sealed systems
- Administrative controls like job rotation, limiting time in hazardous areas
- PPE like masks, gloves, and protective clothing as a last line of defence based on routes of entry
Ventilation systems must be tested and maintained regularly. Under COSHH, local exhaust ventilation must be examined at least every 14 months. PPE should only fill the gap after everything else has been applied.
EH40 and COSHH, What Is the Difference?
These two are often confused but they work together, not instead of each other.
COSHH is the law. It sets your legal duties around hazardous substances.
EH40 provides the numbers. It tells you the specific exposure limits you must not exceed.
If you exceed a WEL listed in EH40, you are almost certainly breaching COSHH at the same time. You cannot comply with one while ignoring the other.
Common Mistakes Employers Make
Knowing what to avoid is just as important as knowing what to do.
Treating PPE as the main control. Masks and gloves are the last resort, not the first solution. Relying on them alone is a compliance failure. Never updating risk assessments. A risk assessment written three years ago may bear no resemblance to how your workplace operates today. Any change in process, materials, or staffing should trigger a review.
Inconsistent monitoring. Monitoring carried out only when an inspector is expected, or only in low-exposure conditions, gives a false picture. It must reflect real working conditions. Ignoring EH40 updates. The HSE revises WELs regularly. If you are working from outdated limits, you may be in breach without even knowing it. Always check the current version on the HSE website.
Misreading the limits. A WEL is not a safe level, it is a maximum. Your goal is always to reduce exposure as far below the limit as reasonably possible, not simply to stay just underneath it.
Key EH40 Updates to Know in 2026
The HSE has taken a tougher stance on several substances in recent years. Notable changes include:
Welding fume, the limit has been effectively reduced to near-zero, and all welding now requires engineering controls such as local exhaust ventilation. PPE alone is not acceptable.
Respirable crystalline silica (RCS), found in stone, concrete, and sand, has had its WEL significantly reduced. Construction and manufacturing employers in particular must review their dust controls.
Engineered nanomaterials and 3D printing emissions are emerging areas where formal guidance is still developing. Employers handling these materials should adopt precautionary controls now.
Always refer to the latest HSE EH40 amendment documents to confirm current limit values.
EH40/2005 Workplace exposure limits
Building a Simple Compliance Programme
You do not need a complex system to be compliant. You need a consistent one. Here is a straightforward framework:
- Identify all hazardous substances in your workplace
- Assess who is exposed, how much, and for how long
- Control exposure using the hierarchy of controls
- Monitor to confirm controls are working
- Record everything, assessments, results, training
- Review regularly and after any significant change
Repeat this cycle continuously. Compliance is not a destination, it is an ongoing process.
Frequently Asked Questions
Is EH40 a legal requirement?
Not directly, but the WELs it contains define “adequate control” under COSHH 2002, which is law. In practice, exceeding a WEL is a breach of COSHH.
How often should I monitor exposure?
It depends on the risk level. High-risk substances or exposures close to the WEL require more frequent monitoring. As a rule, monitor often enough to catch any problem before it harms someone.
What is the difference between TWA and STEL?
TWA is your average exposure over 8 hours. STEL is the maximum for any 15-minute period. You must comply with both.
Who is responsible for compliance?
The employer holds primary legal responsibility. In practice, this extends to every manager and supervisor who oversees work involving hazardous substances.
Final Thoughts
EH40 compliance is not about paperwork. It is about making sure the people who work for you do not develop serious, preventable illnesses because of decisions you made, or failed to make.
In 2026, the regulatory environment is tighter, the science is clearer, and the consequences of getting it wrong are more severe than ever. But the path to compliance is straightforward: know your substances, measure your exposures, control what needs controlling, and keep good records.
Your workers are your most valuable asset. Protecting their health protects your business too.
