- How It Works
- Featured Project
- Insights
How It Works
About WEL Testing
Workplace Exposure Limits (WELs) define the maximum legal concentration of airborne substances employees can be exposed to, averaged over a set time.
We start with a site assessment to identify potential exposure risks from substances like dust, fumes, solvents, or chemicals. This helps determine whether extensive 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 report with findings and mitigation strategies to ensure compliance with COSHH and support a safe, healthy indoor environment.
Service Benefits
- Identify over 500 hazards
- Enhance employee health & saftey
- Vital COSHH compliance
- Evaluate current measures
Featured Project
Finding the source of some puzzling TVOC readings at an office on Regents Street
Objectives
ARM were contacted by a healthy buildings consultant in April 2021 due to unexplainable Total Volatile Organic Compound (TVOC) readings in their office space on Regents Street. The client expressed concerns that the TVOC readings, 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
Resolved
Retrofitted
Insights
Related Insights
Why Choose ARM?
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.
