LEVs Explained: Local Exhaust Ventilation in Labs

When it comes to laboratory safety, one acronym plays a critical role in maintaining air quality and protecting staff from hazardous substances: LEVs – Local Exhaust Ventilation systems.

These systems are a fundamental part of modern lab design, working quietly in the background to capture airborne contaminants at the source, before they can disperse into the room or be inhaled by laboratory personnel. Whether you're specifying new lab installations or reviewing existing systems, understanding the different types of LEVs — including fume cupboards — is key to ensuring both safety and compliance.

What Are LEVs?

LEVs, or Local Exhaust Ventilation systems, are engineered solutions designed to extract airborne contaminants — including fumes, vapours, dust, and aerosols — directly from the source of generation.

A Local Exhaust Ventilation (LEV) system captures contaminants at their source and transports them to a safe location or filter. It typically consists of five main components:

• a hood to capture the contaminants,
• ducting to transport the contaminated air,
• an air cleaner or filter to remove the contaminants,
• a fan to move the air through the system, and
• a discharge point to safely release clean or treated air.

By removing harmful substances before they enter the breathing zone, LEVs help to:

• Improve indoor air quality
• Minimise exposure to hazardous substances
• Meet the legal duties outlined in COSHH (Control of Substances Hazardous to Health) Regulations

Types of LEVs in Laboratory Settings

Not all LEVs are created equal. The appropriate system depends on the type of work being done, the nature of the contaminants, and how mobile or flexible the extraction needs to be.

Here are the most common LEV systems used in laboratories:

1. Fume Cupboards (or Fume Hoods)

These are the most well-known type of LEV and are commonly used for handling volatile chemicals. They create a barrier between the user and the process, drawing contaminated air away and discharging it safely outside (ducted) or through filters back into the room (ductless/recirculating).

Pros:

• High level of containment
• Protects both user and environment
• Ducted options suitable for aggressive vapours

Cons:

• Requires fixed installation
• More expensive than portable options

2. Extraction Arms (Articulated LEVs)

Flexible extraction arms can be positioned directly over a source, offering spot extraction for processes like soldering, microscopy with volatile stains, or small-scale chemical handling.

Pros:

• Highly manoeuvrable
• Cost-effective
• Good for small benchtop tasks

Cons:

• Less effective at containing heavier vapours
• Requires user positioning discipline

3. Enclosed Glove Boxes / Isolators

For ultra-sensitive or hazardous processes (e.g. handling pathogens or cytotoxic drugs), glove boxes offer complete containment with built-in LEV systems.

Pros:

• Maximum user protection
• Fully sealed environment

Cons:

• Expensive and highly specialised
• Limited to very specific tasks

4. Slot Hoods & Downdraught Benches

These provide extraction through narrow slots behind or beneath the work surface, often used in histology or weighing tasks where vertical extraction isn't viable.

Pros:

• Ideal for sensitive balances or dusty processes
• Low-profile design

Cons:

• Less effective if contaminated air rises rapidly
• Not suitable for volatile solvents

LEVs vs General Ventilation: Why Localised Matters

While general room ventilation helps maintain a comfortable working environment, it cannot be relied upon to remove contaminants at source. That’s where LEVs excel. By targeting the emission point, LEVs dramatically reduce airborne concentrations before they disperse — making them far more effective and efficient for managing exposure.

Maintenance and Compliance: LEVs Are Not “Fit and Forget”

Under COSHH, employers must ensure that LEV systems are tested at least every 14 months. A poorly maintained or incorrectly used LEV may give a false sense of security and actually increase risk.

Best practice includes:

• Routine inspections
• User training
• Logbook record keeping
• Regular Thorough Examination and Test (TExT) by a competent person

Conclusion

Whether you're designing a new lab or upgrading your existing facility, LEVs should be a central part of your strategy for safe, compliant working environments. From fume cupboards to flexible extraction arms, understanding your options ensures you can match the right system to the job — keeping your lab clean, compliant, and most importantly, safe.