LEV System Inspection: What Engineers Look for During Compliance Checks

If your workplace generates dust, fumes, mist, or vapour, your local exhaust ventilation (LEV) system is one of the most important pieces of equipment you own. It protects your employees from breathing in harmful substances and your business from legal and compliance risks.

At DevineAir, we work with employers across the UK to help them meet these obligations through professional LEV testing and inspection. It’s essential to understand what engineers actually look for during an LEV system inspection and what you, as an employer, should expect from a proper compliance check.

Why LEV Inspections Matter

Under the Control of Substances Hazardous to Health (COSHH) Regulations 2002, you’re legally required to control airborne contaminants that could harm your workers. One of the main ways to do that is through a properly designed and maintained LEV system.

But installation alone isn’t enough. Regulation 9 of COSHH requires that all LEV systems be thoroughly examined and tested at least every 14 months by a competent person, or more frequently for higher-risk processes.

This inspection confirms that your system still performs effectively and that it’s continuing to protect workers as intended. It also provides documentation you can show to regulators or auditors as proof of compliance.

How is an Inspection Made? 

LEV system inspections aren’t about guesswork. They’re about precision. Engineers follow a clear, step-by-step process to spot potential issues and make sure your system is working exactly as it should. Here’s how they do it.

Step One: Reviewing Documentation

Before they start measuring airflow or inspecting the ducts, engineers usually take a moment to look through your LEV system’s paperwork. This gives engineers a clear picture of how your LEV system was originally designed, how it’s meant to work day to day, and whether anything has changed since it was first installed. They’ll usually look for:

• System design details – drawings, commissioning reports, and design airflow data.
• Previous inspection records – past Thorough Examination and Test (TExT) reports and any follow-up work.
• Maintenance logs – filter changes, fan servicing, duct repairs, or performance checks.
• Operator manuals and procedures – how staff are trained to use and maintain the system.
• Risk assessments and COSHH documents – showing how the LEV fits into your control strategy.

Having complete, up-to-date documentation shows inspectors that you take LEV maintenance seriously, and it makes it easier to identify any performance drift over time.

Step Two: Visual and Structural Inspection

Once the paperwork review is complete, the engineer performs a visual and structural inspection of the system. This is where they look for visible issues that could compromise performance.

Common inspection points include:

• Hoods and inlets – Are they the right type, properly positioned, and free from damage or obstruction? A misaligned hood is one of the most common causes of ineffective LEV.
• Ductwork – Engineers check for holes, corrosion, loose joints, or debris build-up that can restrict airflow.
• Fans and motors – They’ll look for worn belts, damaged blades, unusual noises, or vibration — all signs the fan isn’t operating efficiently.
• Filters and collectors – Filters that are clogged or poorly fitted can cause a drop in airflow or release contaminants back into the air.
• Discharge points – The exhaust should safely vent away from occupied areas, doors, or air intakes.

These checks can reveal whether your system needs basic maintenance or more serious repair before moving on to performance testing.

Step Three: Measuring Performance

The next stage is functional testing. This test confirms that the system is actually controlling contaminants at the source.

Key measurements include:

1. Airflow and capture velocity
   Engineers measure how fast air is moving into each hood or enclosure using calibrated instruments. The readings are compared to design values or HSE guidance to confirm that contaminants are being captured effectively.
   
   
2. Duct velocity and volume flow rate
   These measurements show whether the system is moving enough air to carry contaminants through the ductwork without settling or blocking.
   
3. Static pressure and fan performance
   Engineers use pressure gauges to determine whether the fan is working correctly. A lower-than-expected pressure can point to blockages or leaks.
   
4. Filter pressure drop
   A higher-than-normal reading can indicate that filters are becoming clogged and need replacement.
   
5. Smoke or airflow visualisation tests
   These tests use safe smoke to make airflow patterns visible. It helps show whether contaminants are being captured at the source — or escaping into the operator’s breathing zone.
   

All these readings are recorded, compared against benchmarks, and included in your final inspection report.

Step Four: Assessing Control Effectiveness

LEV systems aren’t just about numbers. Engineers also assess how well the system controls exposure in practice.

They’ll observe how operators use equipment day-to-day:

• Are hoods being used correctly and consistently?
• Have any guards or barriers been removed?
• Are workers positioned outside the airflow zone?
• Are processes generating more fume or dust than the system can handle?

Sometimes, the issue isn’t the system itself. It’s how people are using it. That’s why an inspection often includes recommendations on operator training or simple adjustments that can improve control.

Step Five: Reporting and Recommendations

After completing all tests, the engineer prepares a Thorough Examination and Test report. A compliant report should include:

• A description of the system (location, process, and components)
• Measured test results for airflow and pressure
• Any defects or performance issues found
• An assessment of whether the system is satisfactory, needs attention, or is unsatisfactory
• Recommendations for remedial action
• The name, signature, and qualifications of the competent person who carried out the test

You should keep each report for at least five years, as required by COSHH. This documentation provides evidence that you’re meeting your legal duties if the Health and Safety Executive (HSE) or HSENI inspects your site.

Common Issues Found During LEV Inspections

During inspections across UK workplaces, engineers often encounter the same recurring issues:

• Damaged or poorly positioned hoods that don’t fully capture emissions.
• Leaking or blocked ducts restricting airflow.
• Fans are running too slowly due to belt wear or motor problems.
• Clogged filters that need replacing.
• Systems are modified without re-commissioning, leading to unpredictable performance.
• Lack of staff awareness about how to use or check the system daily.

The good news? Most of these problems are preventable through regular maintenance and operator training.

How to Prepare for Your Next Inspection

You can make your next LEV inspection faster, smoother, and more productive by preparing a few key things in advance:

• Clear space around hoods, ducts, and fans for easy access.
• Gather past inspection and maintenance records.
• Have the system running under normal operating conditions during the test.
• List any known issues or changes since the last inspection.
• Make sure your staff know what’s happening and can assist the engineer if needed.

Preparation not only helps the engineer but also demonstrates that your business takes compliance seriously.

What Happens if Your System Fails the Test?

If your LEV system is found to be unsatisfactory, you must act quickly to fix the issue. This might mean:

• Repairing damaged ductwork or replacing filters.
• Rebalancing the system or increasing airflow.
• Re-training staff on proper use.
• Temporarily improving ventilation or using RPE (respiratory protective equipment) until the system is repaired.

In serious cases where the system isn’t protecting workers, you may need to stop using the process until adequate controls are restored.

Remember, failing to act on an unsatisfactory LEV report can be viewed as a breach of COSHH and may lead to enforcement action by the HSE.

The Cost of Non-Compliance

Beyond the legal aspect, ineffective LEV systems can have real-world consequences:

• Increased staff sickness or respiratory illness.
• Declining morale or staff turnover in affected areas.
• Dust or fume buildup on equipment reduces efficiency and lifespan.
• Reputational damage if incidents occur.

Regular inspections and maintenance cost far less than the consequences of neglect. Think of them as an investment in worker health and operational reliability.

Staying Compliant and Protecting Your Workforce

A proper LEV system inspection is more than a box-ticking exercise.It’s a key part of keeping your team safe, your operations running smoothly, and your business on the right side of compliance. From looking over the original design plans to testing airflow and checking how well controls are working, engineers take a close look at every part of your LEV system to make sure it’s doing its job properly.

At DevineAir, our qualified consultants carry out LEV inspections and testing in line with COSHH requirements, giving you clear, practical feedback on how your systems are performing and how to improve them.

Apart from LEV testing, we also provide a range of environmental and workplace safety services, including air monitoring, noise assessment, cleanroom verification, hand and arm vibration, and lux level assessments.

So, if it’s been more than a year since your last LEV inspection, or if you’re unsure whether your system is performing as it should, now’s the time to act. Contact our team today to discuss innovative solutions we can bring to your LEV system.