Local Exhaust Ventilation (LEV) systems are often installed correctly. Keeping them effective over time is where the real challenge lies.
At Vent-Tech, we often see how many facilities assume that once airflow rates meet the original design specification, the system will continue to perform as intended. In practice, systems rarely remain static. Processes change, ducting is modified, filters gradually load with impure particles, and extraction arms are repositioned to suit production.
While the airflow readings may appear acceptable on paper, at the hood level, capture can still be inadequate.
This is where modern airflow management approaches and smart ventilation system controls are beginning to influence how LEV systems are monitored and operated.
Why Static LEV Systems Gradually Lose Efficiency
Traditional LEV systems operate with fixed airflow settings designed around a specific set of process conditions.
Over time, those conditions rarely remain unchanged. Workshops evolve, equipment is replaced, and additional extraction points are introduced. In some cases, ductwork is altered without revisiting the original airflow design.
In practice, this often leads to uneven airflow distribution across branches and excessive fan operation as the system attempts to maintain extraction. Capture performance at certain hoods can gradually deteriorate even though airflow readings elsewhere in the system appear stable.
Even though air velocity measurements taken within the duct suggest compliance, that doesn’t confirm effective contaminant capture at the source.
Under COSHH Regulation 9, LEV systems must still demonstrate effective performance through a Statutory Thorough Examination and Test at least every 14 months. Airflow readings alone are rarely the full picture.
How Smart Local Exhaust Ventilation Systems Support Airflow Management
A smart LEV system attempts to regulate airflow dynamically rather than operating at a fixed constant rate.
Instead of running every extraction point at full capacity, airflow is adjusted depending on which parts of the system are active. Sensors within the duct network monitor airflow conditions, and dampers respond accordingly to maintain balance across the system.
When implemented correctly, this type of airflow management can stabilise performance across larger installations where multiple extraction points compete for airflow.
It can also reduce unnecessary fan load during periods of partial operation, particularly in facilities where processes run intermittently. For instance, this is often seen in woodworking shops, grinding operations, or batch production environments where extraction points are not all active simultaneously
However, intelligent control should not be confused with corrective design. If duct sizing, hood placement, or system layout are fundamentally incorrect, control systems cannot resolve those underlying issues.
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Practical Site Considerations for Airflow Management
Modern airflow monitoring tools can improve visibility within LEV systems that would otherwise operate largely unseen between statutory inspections.
In some facilities, this helps identify gradual system changes, such as filter loading or airflow imbalance between branches. In others, it simply highlights the reality that workshop processes rarely behave as consistently as the original design assumed.
Older facilities present their own challenges. Ducting networks that have been extended or modified over time do not always respond predictably to automated airflow control. Systems may attempt to redistribute airflow across branches that were never intended to operate simultaneously.
This is often where professional judgement becomes important. Control algorithms do not always reflect the physical constraints of a duct system that has evolved over many years.
Inspection Considerations for Smart Local Exhaust Ventilation Systems
LEV systems that rely on airflow management technology still require careful verification during statutory LEV testing.
Sensors must be calibrated correctly. Damper responses need to behave as expected under operating conditions. Transport velocities within the duct must remain sufficient to prevent particulate settlement.
Where LEV commissioning and maintenance have been consistent, these systems generally perform well. Where maintenance has been inconsistent, system behaviour can become difficult to interpret during inspection. On-site, ventilation systems rarely behave exactly as the design drawings suggest.
LEV performance is not simply a technical discussion about airflow. It sits within a wider occupational health context. According to the UK Health and Safety Executive, around 11,000 deaths each year in the UK are still linked to occupational lung disease. These figures explain why ventilation performance remains central to COSHH exposure control.
Studies reviewing a range of smart ventilation systems, using inputs such as CO₂ levels, humidity, occupancy and temperature response, have reported ventilation energy reductions of up to 60% without compromising indoor air quality. In some cases, air quality performance improved due to more responsive airflow regulation. This data might be more meaningful for general ventilation systems, but it has a similar impact on industrial LEV systems.
A smart LEV system helps calculate the necessary air volume (CFM), based on the design air volume set by the LEV engineer, and adjusts the fan speed accordingly via the VFD (Variable Frequency Drive). Smart LEV systems that use automated blast gates and VFDs can enable facilities to optimise and reduce energy consumption up to 60% while ensuring capture velocity is maintained at the hood.
The objective of installing a smart LEV system does not change. The purpose is not airflow optimisation alone. It is exposure control and creating efficient breathing zones and contaminant concentration zones..
If you are reviewing an existing system, considering improvements to airflow management, or trying to understand how your system is performing in practice, the Vent-Tech team can assist through system reviews to help you better understand how your airflow systems are operating.
Ultimately, statutory testing is not about producing a report. It is about confirming the system continues to control exposure as intended.