The Most Common Reasons Your Fume Cupboard Isn’t Working

A fume cupboard is one of the most important safety systems within any laboratory. Designed to protect users from hazardous fumes, vapours and airborne contaminants, it plays a critical role in maintaining a safe and compliant working environment. However, like any piece of specialist equipment, a fume cupboard can experience issues over time that affect its performance.

Sometimes the warning signs are obvious, such as an airflow alarm sounding or unusual noises coming from the extract system. In other cases, problems can develop gradually and remain unnoticed until routine testing highlights a drop in performance, understanding some of the most common causes can help laboratories identify issues early and avoid unnecessary risks!

Reduced Airflow & Poor Containment

One of the most common reasons a fume cupboard stops performing effectively is a reduction in airflow. Fume containment relies on maintaining the correct face velocity, allowing hazardous fumes to be safely drawn away from the operator and into the extraction system.

If airflow falls below the required level, contaminants may no longer be properly contained. This can increase the risk of exposure and compromise the safety of the entire laboratory environment.

Reduced airflow can occur for several reasons, including partially blocked ductwork, worn extract fans, debris caught within the fans or changes elsewhere in the ventilation system. In many cases, these issues develop slowly, making regular testing and inspection particularly important.

Added information from the Health and Safety Executive (HSE) highlights the importance of maintaining Local Exhaust Ventilation (LEV) systems to ensure they continue to provide effective protection!

Blocked Or Damaged Ductwork

Although the fume cupboard itself is the most visible part of the system, its performance depends heavily on the condition of the extract ductwork and associated components. Damage, corrosion or restrictions within the ducting can significantly reduce airflow and impact containment.

Over time, certain substances may cause deposits to build up inside the system, while ageing ductwork can crack, develop leaks or suffer from general wear – changes to the extract system or poor installation practices can also contribute to performance issues.

These problems are often hidden from view, they may only become apparent during maintenance or formal testing. This is one of the reasons why routine inspections are essential for maintaining reliable operation.

Debris Within The Fan

Over the years, we have removed hundreds of items from the insides of fan cases, usually tissues, gloves, tin foil, etc, but also multiple species of birds (including once, an owl!), footballs, tennis balls and even a bright pink inflated party balloon (we still have no idea how this got in there)!

Sometimes these are drawn up the duct into the fan from within the fume cupboard, sometimes they drop down the open end of the stack into the fan.

Even a small piece of material caught around the impeller within the fan casing can cause significant vibration and a drop in performance. 

If you have a partial drop in performance on your fume cupboard, this is nearly always the first place we would look for the cause of it.

Worn Components and Mechanical Issues

Like any equipment that sees regular use, a fume cupboard is subject to wear and tear. Components such as sash mechanisms, airflow monitors, fans and alarms can all deteriorate over time.

Some of the most common issues may include:

• Faulty airflow alarms that provide inaccurate readings.
• Damaged sash mechanisms that affect safe operation.
• Fan motors that become noisy or lose efficiency.
• General wear affecting seals and moving components.

While these faults may seem relatively minor individually, they can collectively reduce the overall performance of the system, addressing these problems early helps prevent more significant failures and minimises disruption to laboratory operations.

Changes To The Laboratory Environment

Sometimes the issue isn’t with the fume cupboard itself but with the environment around it. Airflow patterns within a laboratory can be influenced by a range of external factors, including air conditioning systems, open doors and windows, or the introduction of new equipment.

Even changes to the layout of the room can create turbulence that affects containment performance, this is particularly important in busy laboratory environments where layouts and workflows evolve over time.

Modern fume cupboards are designed and tested to standards such as BS EN 14175, but maintaining performance still relies on the surrounding environment being suitable for safe operation. Reviewing room conditions and airflow patterns should therefore form part of any ongoing maintenance strategy.

Lack Of Routine Fume Cupboard Testing & Maintenance

Many issues that affect fume cupboards do not occur suddenly. Instead, they develop gradually over months or even years. Without regular testing and maintenance, these problems can go unnoticed until performance has already been compromised.

Routine inspections help identify issues such as airflow changes, component wear and extraction problems before they become serious safety concerns. Fume cupboard testing also provides reassurance that the system continues to operate in line with current standards and performance requirements.

Maintaining accurate service records and following recommended inspection intervals can help laboratories minimise downtime and extend the life of their equipment.

Incorrect Use Of The Fume Cupboard

Even a properly functioning system can struggle to perform effectively if it is not used correctly. Overcrowding the work area, placing large equipment too close to the sash opening or storing unnecessary materials inside the cupboard can disrupt airflow and reduce containment efficiency.

Some common practices that can negatively affect performance include:

• Blocking the face of the fume cupboard or the slots in the rear baffle with equipment or containers.
• Operating with the sash raised higher than recommended.
• Allowing excessive clutter to build up inside the chamber.

Good laboratory practices are just as important as mechanical performance when it comes to ensuring safe operation. Even a well maintained fume cupboard can struggle to provide effective containment if it is not used correctly.

Encouraging good housekeeping, following recommended operating procedures and ensuring staff are properly trained can all help maintain consistent airflow and maximise the level of protection provided by the system. Over time, these simple practices can make a significant difference to both safety and overall performance!

Faults With Monitoring Systems & Controls

Modern fume cupboards are often fitted with airflow monitors and alarm systems that continuously measure performance. These systems provide an additional level of safety by warning users when airflow falls outside acceptable limits.

However, sensors and control systems can themselves develop faults over time, false alarms, inaccurate readings or complete failures may prevent users from recognising genuine performance issues.

Regular calibration and maintenance of these systems help ensure that any alerts are accurate and that the fume cupboard continues to operate safely.

Why Early Intervention Matters

Minor issues can quickly become major problems if they are ignored. A reduction in airflow or a faulty alarm may not immediately stop a fume cupboard from operating, but over time these issues can compromise safety and lead to expensive repairs.

Taking a proactive approach to maintenance and testing allows laboratories to address problems before they escalate, it also helps maintain compliance and provides confidence that the system is continuing to protect laboratory users as intended.

Keeping Your Fume Cupboard Performing At Its Best!

A well maintained fume cupboard should provide years of reliable performance, but like any specialist system, it requires regular attention. Understanding the most common causes of poor performance allows laboratories to identify potential problems early and take corrective action before safety is compromised.

At Fumair, we provide complete support for all makes and models of fume cupboards, including design, installation, testing, maintenance and repairs. Our experienced team works with laboratories across the UK to help ensure systems continue to operate safely, efficiently and in accordance with current standards.

If you are experiencing issues with your fume cupboard or would like advice on maintaining optimum performance, get in touch with our expert team today to discuss your requirements.