Workplace Exposure Limits Testing

How It Works
Featured Project
Insights

How It Works

Workplace Exposure Limits (WEL or WELs), also sometimes referred to as Occupational Exposure Limits, define the maximum legal concentration of airborne substances employees can be exposed to, averaged over a set time.

We start with a site air quality assessment to identify potential exposure risks from substances like dust, fumes, solvents, or chemicals. This helps determine whether extensive IAQ monitoring is needed and what strategy suits your organisation best.

Using advanced air sampling, we measure concentrations against EH40/2005 limits — using either an 8-hour Time Weighted Average (TWA) or 15-minute Short-Term Exposure Limit (STEL).

Monitoring can be personal (in the breathing zone) or fixed (at-source and away), in line with HSG173. For high-exposure environments, such as breweries or ironworks, we account for permissible limits based on practicality.

You’ll receive a clear air quality report with findings and mitigation strategies to ensure compliance with COSHH (EH40/2005) and support a safe, healthy indoor environment.

Benefits of WEL Testing

Identify over 500 hazards
Enhance employee health & safety
Vital COSHH compliance
Evaluate current measures

IAQ Sensors and air quality monitors in an office for workplace exposure monitoring

Check Your Workplace Air Quality Today

Featured Project

Workplace TVOC Measurements for a London Office, Regent's Street

Regents street TVOC measurements for a workplace exposure to VOCs survey

Objectives

ARM were contacted by a healthy buildings consultant in April 2021 due to unexplainable Total Volatile Organic Compound (TVOC) readings in their workspace on Regents Street. The client expressed concerns that the TVOC readings within the office, which were typically within safe limits, would unexpectedly spike at seemingly random times of the day. For this consultant, having unpredictable spikes in air quality readings was a worry as it meant that an appliance or ventilation system might be failing, and if it were to continue to do so the company could be putting their staff at risk of Volatile Organic Compound (VOC) exposure.

Solutions

Discussing the issue with our client, we discovered a pattern of high TVOC readings during days with warmer weather, particularly when the outside temperature reached into the 20-25°C range. Investigating the Air Handling Unit (AHU) outside, we spotted something interesting: the exhaust was placed nearby, and just above, the intake unit. Ordinarily, this shouldn't be a problem, as the exhaust fumes, heated by the inside air, should be hotter than the outside air and therefore rise away from the building. However, on days in which the inside temperature was colder than the outside temperature (let's say the office maintained a temperature of 19°C and the outside temperature was 25°C), these relatively cool exhaust fumes fall to the ground instead of leaving the area. With the position of the intake and the structure of this outside area, the AHU exhaust fumes would just fall to the ground, flood the floor around the intake, and get sucked up into the ventilation system.

This finding still didn't explain why TVOCs were so high while other pollutants were within normal levels. After an investigation of the office space, we realised that the culprit was likely the harsh chemicals being used by the cleaner in the mornings, particularly around the bathrooms. This toxic air was being extracted by the ventilation system, pumped outside, and then sucked back into the ventilation system.

Results

We advised our client to reinstall the AHU exhaust further away and facing the opposite direction. Through subsequent TVOC readings, the client has thankfully not noticed any spikes.

We believe this problem was largely the result of poor planning. To place the exhaust so close to the intake is one mistake, and to place it higher than the intake is a disaster waiting to happen. In this case, we're glad the client noticed the high TVOC levels early, because continued exposure to these pollutants like these can be incredibly harmful to health over extended periods of time. This client contacted us in April, which was lucky because the upcoming summer months would have resulted in increased levels of TVOCs within the building due to the poor placement of the air handling unit's components.

Challenges

High TVOC readings
Undetermined source
Health risks for office staff

"When this client initially contacted us about TVOC spikes picked up by their IAQ sensors, we weren't sure what to make of it. Air quality issues can be tricky to diagnose, but are often very simple issues that would have gone unnoticed without testing or monitoring."

Adam Taylor, CEO of ARM Environments

Wellbeing

Happy & healthy workforce

Resolved

Source of TVOCs found and issue remediated

Retrofitted

AHU exhaust relocated

Insights

WEL Consultation

We discuss the air quality concerns and requirements for your business sector. Then we book a site visit so one of our air quality experts can assess the space and begin testing or monitoring.

Workplace air quality testing
Long-term monitoring
Speak to a professional

WEL Testing Procedure

We assess your air quality against EH40/2005 workplace exposure limits, either long-term or short-term. We then compile our findings into an easy-to-understand report to help you make improvements.

Short-term exposure limit (STEL)
Long-term exposure limit (LTEL)
Understand your air quality

WEL Report Handover

A workplace air quality report from ARM Environments not only ensures that your staff and occupants are safe, but also helps to inform future decisions, like layout changes or ventilation strategies.

Compliance with HSE EH40/2005
We discuss the findings with you
We provide suggestions on what to do next

Which sectors need workplace exposure testing?

Workplace exposure testing is particularly important in industries where employees may be exposed to hazardous dusts, fumes, vapours, gases, chemicals, or other airborne contaminants as part of their work.

WEL Testing can help determine the level of exposure workers are experiencing and whether existing control measures are effectively reducing exposure. Results are compared against the workplace exposure limits (WELs) set by HSE, helping businesses identify potential risks, demonstrate compliance, and make informed decisions about further control measures where required.

Book a Consultation for Your Workplace

We offer WEL testing for...

Manufacturing & Engineering
Construction
Automotive & Transport
Chemical & Pharmaceutical
Waste, Recycling & Utilities
Healthcare & Laboratories
Education & Schools

WEL Testing Methods

WEL air quality monitoring can come in various forms. Real-time digital monitors, active sampling, and passive sampling can all be deployed in different circumstances to gather the most relevant and accurate data for your business or workplace.

For more information on the types of WEL assessment techniques available, read our blog on the various air sampling methods.

Air Sampling Methods Compared

Workplace Exposure Tests

Plastics moulding facility - WEL Testing

Plastics fumes

For plastics & injection moulding, printing & packaging, and other manufacturing facilities in the UK.

Plastics fumes testing

Silica dust

For construction workers cutting, chasing, or drilling concrete and brick, or stone and tile fabrication.

Silica dust testing

Generator fumes

For construction workers deploying portable generators, or any worker concerned about diesel fumes indoors.

Generator fume testing

Wood dust

For woodworking facilities and workshops handling different wood types.

Wood dust testing

Welding fume workplace exposure monitoring - WEL Testing

Welding fumes

For metalworking facilities and workers using welders both indoors with LEV and outdoors with RPE.

Welding fumes testing

Soldering circuitboard without local exhaust ventilation lev - WEL Testing

Soldering fumes

For electronics manufacturers, PCB assembly workshops, and repair technicians using rosin-core solder or flux.

Soldering fume testing

What is WEL exposure testing? ↓

WEL exposure testing (AKA Workplace Exposure Limits Testing) measures airborne concentrations of hazardous substances in the workplace to ensure they do not exceed workplace exposure limits set by COSHH, with specific amounts outlined in EH40/2005.

What is a workplace exposure limit (WEL)? ↓

A workplace exposure limit (WEL) is the maximum concentration of a hazardous substance in workplace air that a worker can be exposed to, averaged over a specified reference period, without an unacceptable risk to health. In the UK, WELs are set and published by the Health and Safety Executive (HSE) in EH40/2005, and cover both long-term exposure limits (8-hour time-weighted average, TWA) and short-term exposure limits (15-minute reference period, STEL). Employers have a legal duty under COSHH (Control of Substances Hazardous to Health) Regulations to ensure exposure to substances with a WEL is reduced as far as reasonably practicable, and in any case kept below the limit.

Why is WEL exposure testing important? ↓

It identifies potential health risks, ensures legal compliance for employers by meeting COSHH obligations, and helps maintain and improve a safe working environment.

How often should WEL exposure testing be conducted? ↓

Testing frequency depends on the specific workplace environment and the substances in use; general dust and inert compounds may only need assessment every two years. Additionally, if previous surveys show good control of exposure, WEL exposure testing can be less frequent. Regular monitoring on at least an annual basis is recommended to ensure ongoing compliance and safety within COSHH.

What substances are commonly tested during Workplace Exposure Testing? ↓

Common substances include chemicals, dusts, fumes, solvents, and biological agents.

Is exposure testing a legal requirement? ↓

Yes. Under COSHH regulations, UK employers must assess and control exposure to hazardous substances. WEL Testing is essential for demonstrating compliance.

What is the Health and Safety at Work Act 1974 and how is it different to WELs? ↓

This act set out the duty of care to ensure employees and the public are kept safe wherever it is "reasonably practicable."

WELs apply under COSHH; by breaching the workplace exposure limits, you violate COSHH. In turn, to violate COSHH is to ignore your duty of care to your employees, therefore breaking the law under the HSWA 1974. Breaching HSWA is a criminal offense that leaves an employer open to prosecution.

What is occupational exposure limits testing? ↓

Occupational Exposure Limits is another term for Workplace Exposure Limits; it means the same thing. HSE, the official government body, use the term WEL, which is why it's more common than OEL.

If you're looking for information on how Occupational Exposure Limits are enforced, learn more here. For testing services, get in touch with our team to book a consultation.

Why Choose ARM for your Workplace Exposure Testing?

At ARM Environments, we don’t just tick compliance boxes – we specialise exclusively in indoor air quality.

Our team holds SafeContractor and BESA certifications, and our CEO chairs BESA’s IAQ Group – placing us at the forefront of UK standards.

Unlike general hygiene contractors, we focus solely on air quality, giving you sharper insight, more precise monitoring, and practical advice rooted in years of sector-specific expertise.

HVAC Technician testing a building's ventilation system

Workplace Exposure Limits Testing